Each marker below carries its technical name, what it measures in plain language, the limits of what it can tell you, and the nutrients known to move it. Where a framework and mainstream practice disagree, both views are shown rather than one being hidden.
Iron Panel (Serum Iron, Ferritin, TIBC, Transferrin Saturation)
Cellular Six: ExchangeThis marker sits in Exchange -- moving iron across boundaries and handing it between carriers.
Serum iron is circulating iron at the moment of the draw; ferritin reflects iron stores (but is also an acute-phase inflammatory protein); TIBC reflects how much transferrin (the iron-carrier protein) is available; transferrin saturation is the percentage of that capacity currently in use.
Typical range: Ferritin ~15-150 ng/mL (women), ~20-250 ng/mL (men), lab-dependent; serum iron ~60-170 mcg/dL; saturation 20-50%; TIBC 250-450 mcg/dL (conventional ranges, consistent with mainstream lab medicine).
How it is used clinically
Ferritin as a positive acute-phase reactant rising independent of iron status is well established [SOLID] -- this is exactly why mainstream labs pair ferritin with CRP/iron saturation rather than reading it alone. "Anemia of inflammation/chronic disease" is a recognized mainstream diagnosis, and its mechanism (hepcidin-driven iron sequestration in macrophages during inflammation) is well described, but this is attributed to hepcidin/inflammatory signaling, not primarily to copper-ceruloplasmin insufficiency. True tissue iron overload in humans is a well-characterized condition (hereditary hemochromatosis, most often HFE gene mutations, or secondary overload from repeated transfusions) that is diagnosed via genetic testing and/or elevated transferrin saturation and ferritin together -- not inferred from "normal" labs. Hemosiderin itself is a real, recognized iron-storage form (seen on biopsy/imaging in genuine overload states), but using it as a routinely-tested marker of subclinical "hidden" overload in people with normal iron panels is not standard practice.
What this framework claims
Robbins argues "ferritin is nothing, hemosiderin is everything" -- that a "normal" or even low ferritin doesn't rule out tissue iron overload, because without adequate ceruloplasmin ferroxidase activity, iron can't be safely loaded into ferritin's storage shell and instead degrades into hemosiderin, a less-regulated iron-storage form that the functional model treats as a marker of chronic iron mishandling. The functional model also argues that a large share of "anemia of chronic disease/inflammation" is actually a copper-ceruloplasmin problem (iron stuck in tissue, unable to move) rather than a true iron shortage, and warns against iron supplementation in this pattern because it can add fuel to an already-dysregulated system.
Nutrients that move it
- Copper/ceruloplasmin (mechanistic support for the functional model's model)emerging -- in mice engineered to lack both multicopper ferroxidases (hephaestin and ceruloplasmin), animals developed severe anemia and low serum/spleen iron *alongside* iron overload in the liver, heart, kidney, and duodenum -- a real, published finding that does partially mirror the functional model's "low serum iron with tissue overload" picture. (source: Fuqua BK et al., Cellular and Molecular Gastroenterology and Hepatology, 2018) A separate mouse study found dietary copper deficiency alone (not full ferroxidase gene knockout) caused anemia, duodenal hypoxia, and altered iron-absorption gene expression. (source: Matak P et al., PLOS ONE, 2013) **Important caveat:** these are severe genetic-knockout or induced-deficiency animal models, not evidence that ordinary, mild nutritional copper insufficiency produces this pattern in humans with normal genes -- extrapolating from double-knockout mice to "most fatigued adults have this" is the functional model's leap, not something demonstrated in human trials.
- Vitamin Csolid -- enhances non-heme iron absorption; meta-analyses of iron-deficiency-anemia trials show a small but real boost to hemoglobin/ferritin when added to iron supplementation. (source: systematic review/meta-analysis, ASH Blood Vessels Thrombosis & Hemostasis, 2024)
- Riboflavin (B2)emerging -- The functional model claims B2 is required to mobilize iron out of storage. There is real, if limited, supporting evidence: riboflavin-dependent enzymes participate in reductively releasing iron from ferritin, riboflavin deficiency impairs iron mobilization in animal models, and population studies link inadequate riboflavin intake to higher anemia risk; a supplement trial in mildly anemic populations showed riboflavin enhanced the hemoglobin response to standard iron treatment. This is real, but modest, supportive evidence -- not proof that B2 is a primary driver of most iron-panel abnormalities. (source: Nutrition Reviews, 2023; Jiangsu Nutrition Study, PMC3923059)
Food first: Heme iron (red meat, poultry, fish) is more bioavailable than plant iron; pair plant iron with vitamin C; ensure adequate riboflavin (dairy, eggs, leafy greens, organ meats) and copper (liver, shellfish) as supporting cofactors.
When to see someone: Iron overload -- from hereditary haemochromatosis or from sustained over-supplementation -- causes irreversible damage to the liver, heart and pancreas, so a confirmed deficiency should come before iron is added. A genuinely abnormal panel, particularly a raised transferrin saturation with a raised ferritin, warrants a standard workup including consideration of HFE genetic testing rather than a self-directed mineral protocol. Ferritin is always read alongside CRP.
Read the studies on Iron Panel (Serum Iron, Ferritin, TIBC, Transferrin Saturation)High-Sensitivity C-Reactive Protein (hs-CRP)
Cellular Six: MaintainThis marker sits in Maintain -- the cleanup and defence system, and whether it is switched on.
A liver-produced marker of systemic inflammation, standard in cardiology risk assessment.
Typical range: <1.0 mg/L low cardiovascular risk, 1.0-3.0 average, >3.0 high risk (standard AHA/CDC cutoffs).
How it is used clinically
This particular use -- pairing CRP with ferritin to sort out whether ferritin is elevated due to inflammation versus true iron stores -- is actually standard, mainstream laboratory-medicine practice, not an the functional model-specific innovation. **[SOLID]** Where the functional model diverges is in attributing the underlying inflammation itself primarily to copper/iron/magnesium mineral dysregulation rather than the broader, well-established list of drivers (diet, adiposity, infection, autoimmune activity, smoking, poor sleep, etc.).
What this framework claims
the functional model uses hs-CRP as a companion marker to the iron panel -- specifically to help decide whether an elevated or "normal" ferritin is being driven by inflammation (masking a true iron problem) rather than genuine iron stores, and treats persistent inflammation itself as a downstream sign of the mineral-dysregulation/oxidative-stress model.
Food first: Mediterranean-pattern eating, weight management, smoking cessation -- these move hs-CRP more reliably than any single mineral intervention.
When to see someone: hs-CRP rises with any acute infection, injury, or recent exercise/dental work -- a single elevated reading isn't meaningful in isolation.
Read the studies on High-Sensitivity C-Reactive Protein (hs-CRP)Serum Copper
Cellular Six: ExchangeThis marker sits in Exchange -- moving iron across boundaries and handing it between carriers.
Total circulating copper, of which roughly 95% is normally bound to ceruloplasmin and about 5% is loosely bound to albumin and small peptides (the "free" or "non-ceruloplasmin-bound" fraction).
Typical range: Roughly 70-140 mcg/dL for men, 80-155 mcg/dL for women (ranges vary somewhat by lab/method).
How it is used clinically
Serum copper is used mainly to screen for overt copper deficiency (rare, usually from malabsorption, bariatric surgery, or chronic excess zinc intake) or Wilson's disease/copper overload, alongside ceruloplasmin. It's a recognized positive acute-phase reactant [SOLID] -- it rises with inflammation, infection, pregnancy, and estrogen (including oral contraceptives), which is a real and important interpretive caveat but is a different mechanism than the functional model's "bioavailability" framing.
What this framework claims
Robbins argues total serum copper alone is close to meaningless, because it doesn't tell you how much of that copper is actually "bioavailable" -- i.e., properly incorporated into functional ceruloplasmin versus floating "unbound." the functional model treats a "normal" total copper as potentially masking a functional copper deficiency.
Nutrients that move it
- Zinc antagonismsolid -- chronic high-dose zinc intake (>40 mg/day) induces intestinal metallothionein, which binds copper and blocks its absorption; this is a well-documented, mainstream-recognized cause of copper deficiency, not an the functional model-specific claim.
- Retinol/vitamin Aemerging -- see Ceruloplasmin section below; retinoic acid can induce ceruloplasmin gene expression in cell models, which is the mechanistic basis for the functional model's copper + retinol pairing, but this is early-stage/cell-culture evidence, not a clinical trial in humans with "low energy."
Food first: Beef/chicken liver, oysters and shellfish, cacao are copper-dense whole foods the functional model favors; standard nutrition guidance agrees these are good copper sources for people with confirmed low intake or deficiency.
When to see someone: Copper has a genuinely narrow window in both directions. Overload is Wilson's disease, a genetic condition causing serious liver and neurological damage that needs hepatology or genetics management. A raised serum copper on its own should prompt checking ceruloplasmin and ruling out inflammation, pregnancy or oestrogen therapy -- all of which raise it -- before it is read as dysregulation.
Read the studies on Serum CopperSerum Ceruloplasmin
Cellular Six: ExchangeThis marker sits in Exchange -- moving iron across boundaries and handing it between carriers.
The major copper-transport protein made in the liver; it carries the large majority of circulating copper and functions as a ferroxidase enzyme, oxidizing ferrous iron (Fe2+) to ferric iron (Fe3+) so iron can bind to transferrin and be moved and stored safely. This ferroxidase role is well-established, mainstream biochemistry. **[SOLID]** (source: Vashchenko G, MacGillivray RT, Nutrients, 2013; StatPearls, NCBI Bookshelf)
Typical range: Roughly 20-40 mg/dL in most adult reference ranges (some labs cite 27-37 mg/dL); varies by assay.
How it is used clinically
Ceruloplasmin is primarily used clinically to screen for Wilson's disease (characteristically low) and to help confirm copper deficiency; it is also a well-established positive acute-phase reactant [SOLID] -- levels rise during infection, inflammation, tissue injury, and pregnancy/estrogen exposure. This matters directly for the functional model's framing: a "normal" or even elevated ceruloplasmin during an inflammatory state doesn't necessarily mean someone is copper-replete and metabolically healthy, and a "low-normal" reading isn't automatically a sign of an underlying, correctable "bioavailable copper" deficiency the way the functional model frames it. (cite: StatPearls, NCBI Bookshelf; Inflammation Research review)
What this framework claims
Robbins treats ceruloplasmin as the single most important lab in the protocol -- low or "sub-optimal" ceruloplasmin is, in the functional model's model, the functional bottleneck that lets iron and copper go "unbound" and drive oxidative stress and fatigue. the functional model asserts ceruloplasmin synthesis specifically requires adequate magnesium plus retinol (true vitamin A), and pushes cod liver oil and magnesium supplementation on this basis from day one of the protocol.
Nutrients that move it
- Coppersolid -- copper is ceruloplasmin's direct structural substrate (six copper atoms per molecule); without adequate copper, ceruloplasmin cannot be made, regardless of other nutrient status.
- Retinol/vitamin Aemerging -- retinoic acid (a vitamin A metabolite) has been shown to induce ceruloplasmin gene expression and rescue ceruloplasmin secretion specifically in Wilson's-disease-patient-derived liver cells in a lab-dish (in vitro) model. (source: PMC9616579) This gives the functional model's retinol-ceruloplasmin pairing a real mechanistic basis, but it's disease-specific, cell-culture evidence -- it does not show that giving healthy or mildly fatigued people extra retinol meaningfully raises their ceruloplasmin or resolves symptoms.
- Magnesium (functional-model assertion, not established in peer-reviewed literature) -- Robbins states magnesium is directly required for ceruloplasmin synthesis. Magnesium's broad role as a cofactor in protein synthesis and hundreds of enzymatic reactions is [SOLID], well-documented physiology, but a specific, dedicated magnesium-to-ceruloplasmin-synthesis pathway was not found in the peer-reviewed literature searched for this file. This specific claim should be treated as the functional model's extrapolation from magnesium's general biochemical importance, not a demonstrated mechanism.
Food first: Copper-rich foods (liver, shellfish) support the substrate side; retinol-rich foods (liver, egg yolk, dairy fat, cod liver oil) are the the functional model-favored vitamin A source, on the theory that preformed retinol (not beta-carotene) is what's needed.
When to see someone: A low ceruloplasmin together with a high non-ceruloplasmin-bound ("free") copper and/or neurological or liver symptoms warrants a Wilson's disease workup with a specialist -- this is a serious genetic condition, not something to self-manage with a mineral protocol.
Read the studies on Serum CeruloplasminReticulocyte Hemoglobin (Ret-He / CHr)
How much haemoglobin is actually being packed into the newest red blood cells, made in the last few days. Because reticulocytes are young, this is close to a real-time readout of the iron supply reaching the bone marrow, where ferritin reports a storage balance accumulated over months. **[SOLID]** (source: Transferrin saturation versus reticulocyte hemoglobin content for iron deficiency, 2003)
Typical range: Commonly reported around 28-35 pg depending on analyser, with values below roughly 28 pg treated as suggesting functional iron restriction. Analyser-dependent, so use the reporting laboratory's range.
How it is used clinically
Well established in laboratory haematology and directly compared against transferrin saturation for detecting iron-deficient erythropoiesis. It is often already available on modern analysers as part of a full blood count, which means it can sometimes be added at no extra draw and little extra cost.
Nutrients that move it
- Ironsolid -- the direct input, and the reason the marker moves quickly when supply changes.
- Vitamin B12 and folatesolid -- both are required to build red cells at all, so a shortfall in either changes cell production independently of iron and has to be read alongside it.
- Coppersolid -- copper deficiency produces an anaemia that does not respond to iron, and this marker will stay low through iron repletion if copper is the actual limit.
Food first: The same levers as iron repletion, with the advantage that this marker will tell you within a couple of weeks whether they are landing.
When to see someone: Analyser-dependent, and not comparable between laboratories using different instruments. Track it in the same lab or the trend means nothing.
Read the studies on Reticulocyte Hemoglobin (Ret-He / CHr)Soluble Transferrin Receptor (sTfR)
Cellular Six: ExchangeThis marker sits in Exchange -- moving iron across boundaries and handing it between carriers.
How loudly the tissues are asking for iron. Cells that need iron put more transferrin receptors on their surface, and a soluble fragment of those receptors appears in the blood. Unlike ferritin, sTfR is not an acute-phase reactant, so it does not rise with inflammation -- which is precisely why it is useful when ferritin cannot be trusted. **[SOLID]** (source: Iron-related Biomarkers in the Diagnosis and Management of Iron Disorders, 2024)
Typical range: Assay-specific. Frequently reported alongside the sTfR/log-ferritin index, which combines demand and storage into one figure and separates the two common pictures more cleanly than either number alone.
How it is used clinically
Recognised in the laboratory literature as a useful adjunct where inflammation confounds ferritin, and used in exactly that way in the diagnostic literature comparing iron-deficiency anaemia with anaemia of chronic disease. Availability and cost, rather than validity, are the usual reasons it is not ordered.
Nutrients that move it
- Ironsolid -- sTfR falls as tissue iron supply is genuinely restored, which makes it a reasonable marker of whether repletion is actually working rather than merely raising a storage number.
- Vitamin Aemerging -- vitamin A status influences the mobilisation of stored iron, one of several places where the iron system depends on a nutrient that is not iron.
- Coppersolid -- the ferroxidase step again: demand signalling does not help if the loading step is impaired.
Food first: Where sTfR is genuinely raised, the tissues are asking for iron and the usual food levers apply: haem iron from red meat and shellfish, non-haem sources paired with vitamin C, and attention to whatever is limiting absorption.
When to see someone: sTfR is not affected by inflammation, but it IS raised by anything that increases red cell production, including haemolysis and recent altitude exposure. Read it beside a blood count rather than alone.
Read the studies on Soluble Transferrin Receptor (sTfR)Hepcidin
Cellular Six: ExchangeThis marker sits in Exchange -- moving iron across boundaries and handing it between carriers.
The hormone that controls how much iron enters the bloodstream at all. Made in the liver, hepcidin binds the iron exporter ferroportin on gut and macrophage cells and degrades it, which shuts the door on both dietary absorption and the recycling of iron out of storage. It is the master regulator, and it is the reason iron status is a question of traffic control rather than intake. **[SOLID]** (source: Hepcidin and Iron in Health and Disease, 2023)
Typical range: Assay-dependent and not yet standardised across laboratories, which is the main practical limitation of ordering it. Interpret it against the reporting range of the specific lab, and against ferritin and CRP drawn at the same time.
How it is used clinically
Hepcidin's regulatory role is established biochemistry and is central to how anaemia of inflammation is understood. Its use as a routine clinical test is still limited, mainly because assays are not harmonised between laboratories. It is best read as an explanatory marker alongside ferritin, transferrin saturation and CRP rather than as a standalone number.
Nutrients that move it
- Vitamin Csolid -- improves absorption of non-haem iron at the gut, which matters most when hepcidin is not elevated. It does not override a hepcidin block.
- Copper and ceruloplasminsolid -- iron cannot be loaded onto transferrin without ferroxidase activity, so the copper side of the system sits directly upstream of whether absorbed iron becomes usable.
- Addressing the inflammation itselfsolid -- because hepcidin follows inflammatory signalling, the lever that moves it is whatever is driving that signal, not more iron.
Food first: There is no food that lowers hepcidin directly. The honest answer is that this marker points upstream: it tells you to look for the inflammatory driver rather than to add iron, and adding iron against a high hepcidin is the specific mistake it exists to prevent.
When to see someone: A raised hepcidin with low serum iron is not a reason to supplement iron. Iron given into an inflammatory state is poorly absorbed and adds oxidative load. This is one of the clearest cases where the correct action is the opposite of the intuitive one.
Read the studies on HepcidinVitamin B12 & Folate
Cellular Six: BuildThis marker sits in Build -- the raw material for making and renewing structure.
Two cofactors that work as a pair. Both are required to build red blood cells and to run methylation, the reaction that recycles homocysteine and builds neurotransmitters. Because they overlap, folate can mask a B12 shortfall in the blood count while the neurological cost of that shortfall continues -- which is why they are read together rather than separately.
Typical range: Standard B12 is roughly 200-900 pg/mL, a range set to catch frank deficiency rather than sufficiency. Functional-optimal (opinion): above about 400-500 pg/mL is commonly cited. Serum B12 is an imperfect measure of what is inside the cell, which is why methylmalonic acid is the better follow-up when symptoms and serum disagree.
Nutrients that move it
- B12 from animal foods, or supplemented on a plant-only patternsolid -- B12 is made by bacteria and reaches humans through animal foods. A fully plant-based pattern has no reliable food source, which makes supplementation or fortified foods a structural requirement rather than an optimisation.
- Folate from food, and the folic acid distinctionsolid -- Folate from leafy greens, legumes and liver is not the same molecule as synthetic folic acid in fortified flour. The two are handled differently, and this is a place where the form on the label matters.
- What depletes thememerging -- Long-term metformin and acid-suppressing medication both reduce B12 absorption -- a systematic review of 40 studies examined how micronutrients and metformin interact. Alcohol and low stomach acid also reduce uptake. A shortfall here is more often absorption than intake.
Food first: Liver, shellfish, oily fish, eggs and dairy for B12; nutritional yeast and fortified foods on a plant-only pattern. Dark leafy greens, legumes, asparagus and avocado for folate. Cooking water leaches folate, so steam rather than boil.
Read the studies on Vitamin B12 & FolateMethylmalonic Acid (MMA)
A more specific and sensitive marker of vitamin B12 status than serum B12 itself, especially useful when B12 sits in a borderline range.
Typical range: Standard: under 0.4 micromol/L typically normal (assay-dependent); elevated MMA with borderline-low B12 confirms true B12 deficiency at the cellular level.
Nutrients that move it
- Vitamin B12 -- Required as a cofactor for L-methylmalonyl-CoA mutase; when B12 is insufficient, MMA accumulates. Considered the most reliable functional marker of B12 deficiency, more specific than homocysteine.
Food first: Animal products (meat, fish, eggs, dairy) or fortified foods/supplements for vegans; absorption also requires adequate stomach acid and intrinsic factor.
When to see someone: A raised MMA alongside a normal B12 can also reflect reduced kidney function or, rarely, another metabolic condition -- so it is read next to kidney function rather than taken on its own as proof of B12 deficiency.
Read the studies on Methylmalonic Acid (MMA)Homocysteine
Cellular Six: BuildThis marker sits in Build -- the raw material for making and renewing structure.
The level of an amino acid byproduct of protein metabolism that reflects how well B-vitamin-driven remethylation is converting it back to methionine.
Typical range: Standard: 4-15 micromol/L (lab-dependent), with above 15 often used as a cutoff suggestive of B12/folate insufficiency. Functional-optimal (opinion): under 7-8 micromol/L commonly cited as a better cardiovascular-risk target, tighter than the standard upper limit.
Nutrients that move it
- Vitamin B12 -- The cofactor for methionine synthase, the enzyme that converts homocysteine back to methionine; homocysteine rises predictably as B12 status declines and normalizes with repletion.
- Vitamin B9 (Folate) -- Donates the methyl group used in the same reaction; folate deficiency raises homocysteine independent of B12 status, and the two nutrients are frequently deficient together.
- Vitamin B6 -- Required for the alternate (trans-sulfuration) pathway that clears homocysteine; B6 deficiency also raises levels.
Food first: Leafy greens and legumes (folate), animal products/fortified foods (B12), poultry/fish/potatoes/bananas (B6).
When to see someone: Kidney disease independently raises homocysteine regardless of B-vitamin status -- always interpret alongside kidney markers (eGFR/creatinine). Very high-dose B6 (>100mg/day long-term) can cause peripheral neuropathy.
Read the studies on HomocysteineIntrinsic Factor Antibody and Parietal Cell Antibody (Pernicious Anemia)
Antibodies seen in autoimmune (pernicious) anemia, one of the most common causes of true vitamin B12 deficiency in adults -- intrinsic factor antibodies block the protein needed to absorb B12 in the gut; parietal cell antibodies attack the stomach cells that make both intrinsic factor and stomach acid.
Nutrients that move it
- Vitamin B12solid -- B12 deficiency from pernicious anemia is managed with B12 replacement (typically injectable/high-dose oral or sublingual, since intrinsic-factor-dependent gut absorption is impaired), not by "curing" the underlying autoimmune attack on parietal cells or intrinsic factor. (source: NIH ODS Vitamin B12 Health Professional Fact Sheet)
Food first: Once diagnosed, B12 repletion via a route that bypasses the intrinsic-factor absorption step (IM injection, high-dose oral B12 which has a small intrinsic-factor-independent absorption pathway, or sublingual) is the standard, evidence-based approach.
When to see someone: Pernicious anemia is a lifelong condition requiring ongoing B12 monitoring/repletion, and it raises long-term risk of gastric carcinoid tumors and gastric cancer due to chronic atrophic gastritis -- this needs gastroenterology follow-up (periodic endoscopic surveillance in some cases), not just a B12 supplement.
Read the studies on Intrinsic Factor Antibody and Parietal Cell Antibody (Pernicious Anemia)Hemoglobin, Hematocrit, RBC Count, MCV & RDW
The oxygen-carrying red blood cell system -- total oxygen-carrying capacity, average red cell size, and how much red cell sizes vary.
Typical range: Standard: Hemoglobin 13.5-17.5 g/dL (men), 12.0-15.5 g/dL (women); MCV 80-100 fL; RDW 11.5-14.5%.
Nutrients that move it
- Iron -- Deficiency classically causes microcytic (low MCV) anemia with elevated RDW as cell sizes become more variable during the deficiency process; correcting deficiency normalizes these over weeks to months.
- Vitamin B12 -- Deficiency causes macrocytic (high MCV) anemia, since B12 is needed for DNA synthesis during red cell division; correcting the deficiency reverses the macrocytosis.
- Vitamin B9 (Folate) -- Same macrocytic-anemia mechanism as B12 -- both are needed for DNA synthesis during red cell division.
- Copper -- Deficiency can cause anemia (sometimes microcytic, sometimes normocytic) due to copper's role in iron mobilization; uncommon but seen with chronic excess zinc intake displacing copper.
Food first: Address the specific deficiency identified (iron-rich foods + vitamin C for absorption if microcytic; B12/folate-rich foods or supplementation if macrocytic).
When to see someone: Confirm before correcting. A mixed deficiency can normalise MCV while both problems are still present, so concurrent iron and B12 shortfall can hide behind an ordinary-looking number. Pair the CBC with the iron panel or B12/folate/MMA rather than reading it alone.
Read the studies on Hemoglobin, Hematocrit, RBC Count, MCV & RDWZinc and the Zinc:Copper Ratio
Cellular Six: ExchangeThis marker sits in Exchange -- moving iron across boundaries and handing it between carriers.
Serum zinc reflects circulating zinc status (an imperfect marker, since most zinc is intracellular); the zinc:copper (or copper:zinc) ratio compares the two minerals, which compete for absorption via intestinal metallothionein.
Typical range: Serum zinc roughly 60-120 mcg/dL. A reference interval for the plasma copper/zinc ratio of about 0.54-1.68 has been established in healthy women of childbearing age; the functional model and some functional-medicine sources cite a narrower "optimal" ratio of roughly 0.7-1.0, which is an opinion range, not a diagnostic cutoff. (source: Nutrients, 2021, PMC7999022)
How it is used clinically
The zinc-copper antagonism itself (high-dose zinc inducing metallothionein, which binds and blocks copper absorption) is well-established, mainstream physiology [SOLID], and is the basis of a recognized clinical entity: zinc-induced copper deficiency, usually from chronic high-dose zinc supplementation or denture-cream misuse, causing myeloneuropathy and anemia. Using the specific ratio as a routine wellness marker for anxiety, mood, or hormone symptoms in the general population is **[CONTESTED]** -- reference intervals for the ratio exist, but tying specific ratio bands to those symptoms hasn't been established in controlled studies.
What this framework claims
the functional model watches this ratio closely, treating a copper-dominant or zinc-dominant imbalance as a driver of symptoms (copper excess linked to anxiety/estrogen dominance in the functional model writing; zinc excess linked to blunted immunity and copper deficiency).
Nutrients that move it
- Zinc and immune functionsolid -- zinc lozenges/supplementation shortens common cold duration in meta-analysis (see Function Health panel file for citation).
Food first: Balance zinc-rich foods (oysters, red meat, seeds) with copper-rich foods (liver, shellfish, cacao) rather than supplementing either in isolation long-term without monitoring.
When to see someone: Chronic zinc supplementation above ~40 mg/day risks copper deficiency and its neurological/hematologic consequences; anyone on long-term zinc should have copper status periodically checked.
Read the studies on Zinc and the Zinc:Copper RatioRetinol (Vitamin A)
Cellular Six: BuildThis marker sits in Build -- the raw material for making and renewing structure.
Serum retinol reflects circulating, "storage-form" vitamin A status, though serum levels are homeostatically buffered and don't fall until liver stores are substantially depleted.
Typical range: Roughly 20-60 mcg/dL in most adult reference ranges (some labs cite 28-86 mcg/dL); levels at or below ~20 mcg/dL suggest moderate deficiency, ≤10 mcg/dL suggests severe deficiency.
How it is used clinically
Retinol's role in normal hematopoiesis (red blood cell production) and immune function is well-established [SOLID] mainstream nutrition science, and severe vitamin A deficiency is a recognized cause of anemia in deficient populations. Retinoic acid inducing ceruloplasmin expression has real in vitro support (see Ceruloplasmin section). Where mainstream and the functional model diverge: the functional model's claim that most people in food-secure countries are meaningfully retinol-deficient despite normal labs, and that this deficiency is a major driver of everyday fatigue, is **[CONTESTED]** -- overt vitamin A deficiency is uncommon in well-nourished populations, and there is no clinical trial showing that supplementing retinol above sufficiency in non-deficient adults improves fatigue or ceruloplasmin function.
What this framework claims
the functional model holds that most people are functionally retinol-insufficient despite "normal" serum levels, that only preformed, animal-sourced retinol (not plant beta-carotene) can be efficiently used to build ceruloplasmin and support red blood cell production, and recommends cod liver oil from the start of the protocol on this basis, citing historical (19th-century) use of cod liver oil for anemia and mid-20th-century research on vitamin A deficiency and blood formation.
Food first: Liver, egg yolks, full-fat dairy, and (per the functional model) cod liver oil are preformed-retinol sources; orange/yellow vegetables provide beta-carotene, a precursor the body converts to retinol at a variable and self-limiting rate.
When to see someone: Preformed vitamin A (retinol, as in cod liver oil and liver) has real toxicity risk that beta-carotene does not. Intakes above roughly 10,000 IU/day (3,000 mcg RAE) of preformed retinol during pregnancy are linked to increased birth-defect risk, with clearer teratogenic signal above 25,000-30,000 IU/day; a single very high acute dose (>100,000 IU) in early pregnancy is a recognized teratogenic risk. (cite: Rothman KJ et al., NEJM, 1995; EFSA Scientific Opinion, 2024) Pregnant or potentially pregnant women should not start high-dose cod liver oil or retinol supplementation without discussing dose with a clinician. Chronic high-dose preformed vitamin A in anyone can cause liver toxicity, bone pain, and headaches (hypervitaminosis A).
Read the studies on Retinol (Vitamin A)Magnesium RBC (Red Blood Cell Magnesium)
Cellular Six: TransformThis marker sits in Transform -- the cofactors enzymes need to turn fuel into usable energy.
Magnesium concentration inside red blood cells, which -- because RBCs live about 120 days -- reflects a longer-term, more stable snapshot of intracellular magnesium status than serum magnesium, which represents less than 1% of total body magnesium and can shift acutely with stress hormones. This physiological rationale (serum magnesium as a poor proxy for tissue status) is well-supported. **[SOLID]**
Typical range: Roughly 4.0-6.8 mg/dL depending on the lab (e.g., Quest ~4.0-6.4 mg/dL, LabCorp ~4.2-6.8 mg/dL).
How it is used clinically
RBC magnesium is a legitimate research and specialist-clinical tool, and there is real physiological support for the idea that serum magnesium can be misleading: in one classic study, intravenous epinephrine significantly lowered serum magnesium without changing free intracellular RBC magnesium (measured by NMR), showing that acute stress can drop serum readings without reflecting true tissue depletion. (cite: Joborn H et al., PMID 2187026) That said, RBC magnesium is not part of routine primary-care panels, and clinical chemistry does not treat it as a perfected "gold standard" -- there's ongoing debate about which test (serum ionized magnesium, total serum magnesium, RBC magnesium, or a magnesium-loading/retention test) best reflects true body magnesium status; RBC magnesium is a reasonable, evidence-supported option, not a settled superior standard the way the functional model sometimes implies. **[EMERGING/SOLID, mixed]**
What this framework claims
the functional model considers RBC magnesium a meaningfully better status marker than serum magnesium and central to the whole protocol, targeting the upper part of the reference range or above.
Nutrients that move it
- Magnesium and ATP/enzymatic functionsolid -- magnesium is a required cofactor for several hundred enzymatic reactions and stabilizes the negative charges on ATP's phosphate groups, a foundational and uncontested piece of biochemistry. (source: de Baaij JH, Hoenderop JG, Bindels RJ, Clinical Kidney Journal, 2012)
- Magnesium and blood pressuresolid -- meta-analysis of 38 RCTs found magnesium supplementation modestly lowers blood pressure, more so in hypertensive/hypomagnesemic people. (source: Hypertension journal meta-analysis, 2025 -- see Studies library, Vitamins/Minerals section)
- Magnesium and glycemic controlemerging -- modest HbA1c/glucose improvement in magnesium-deficient or diabetic populations (see Function Health panel file for full citation detail).
Food first: Leafy greens, nuts, seeds, legumes, whole grains, dark chocolate; supplemental forms like magnesium glycinate or citrate are generally better tolerated than oxide.
When to see someone: Anyone with reduced kidney function (low eGFR) needs medical guidance before supplementing magnesium at the functional model-recommended doses -- magnesium is renally cleared and can accumulate to dangerous levels in kidney disease. High-dose oral magnesium commonly causes diarrhea before anything more serious in people with normal kidneys.
Read the studies on Magnesium RBC (Red Blood Cell Magnesium)Whole-Blood / Hair Mineral Analysis (HTMA)
Cellular Six: TransformThis marker sits in Transform -- the cofactors enzymes need to turn fuel into usable energy.
Hair tissue mineral analysis (HTMA) measures mineral and trace-element concentrations in a hair sample, marketed as a window into longer-term tissue mineral status; the functional model sometimes references whole-blood or hair testing as a supplementary way to assess mineral patterns beyond a standard serum panel.
Typical range: No standardized reference ranges exist across labs; each commercial HTMA lab uses its own ranges and often its own proprietary "ratio" interpretive system.
How it is used clinically
HTMA's reliability is genuinely contested even outside the functional model specifically. **[CONTESTED]** A landmark study sent split samples from a single healthy volunteer to six US commercial hair-testing labs and found more than 10-fold differences in reported concentrations for 12 different minerals between labs. (cite: JAMA, 2001, PMID 11150111) More recent work confirms that intra- and inter-laboratory reliability for HTMA remains inconsistent and heavily dependent on which lab and methodology is used, and correlation between hair mineral levels and actual serum/tissue status is weak to moderate for most minerals (hair zinc versus serum zinc correlates only weakly, for example). (cite: PMC3582931) HTMA is on firmer ground for detecting toxic heavy metals (lead, mercury, cadmium, arsenic), where peer-reviewed and CDC/ATSDR biomonitoring methods have more established validity -- but using it to diagnose "metabolic types," mineral-ratio-based disease patterns, or to guide the functional model's specific mineral-dosing decisions is not supported by controlled clinical evidence.
What this framework claims
HTMA and mineral-ratio analysis are used by some the functional model-adjacent practitioners to infer "oxidation type," adrenal/thyroid patterns, and mineral dysregulation not visible on standard blood work.
Food first: N/A.
When to see someone: Don't make major supplementation decisions (especially involving iron, copper, or high-dose minerals) based solely on an HTMA result -- confirm with standard serum/blood testing, since HTMA's inter-lab reliability for general mineral status is weak.
Read the studies on Whole-Blood / Hair Mineral Analysis (HTMA)Lead
The level of a toxic heavy metal with no known safe or beneficial level in the body, accumulating in bone and affecting the brain, kidneys, and cardiovascular system with chronic exposure.
Typical range: Standard: under 3.5 mcg/dL is the current CDC reference/action level for adults -- there is no optimal nonzero level; lower is always better.
Nutrients that move it
- Calcium -- Competes with lead for absorption in the gut and for storage sites in bone; a randomized placebo-controlled trial in pregnant women found calcium supplementation reduced blood lead levels by about 11% compared to placebo.
- Iron -- Iron deficiency increases intestinal lead absorption (the gut appears to substitute lead for iron when iron is scarce); iron repletion in iron-deficient individuals modestly lowers blood lead.
- Vitamin C -- Observational data associates adequate vitamin C status with lower lead absorption, though dedicated high-quality RCT evidence is thinner than for calcium/iron.
- Zinc -- Observational data associates adequate zinc status with lower lead absorption, though dedicated high-quality RCT evidence is thinner than for calcium/iron.
Food first: Ensure adequate dietary calcium, iron, and vitamin C, especially in children and pregnant women (the highest-risk groups for lead's neurodevelopmental effects).
When to see someone: Nutritional strategies reduce absorption of *ongoing* low-level exposure -- they do not treat significant lead toxicity, which requires medical evaluation and, in some cases, chelation therapy. Any meaningfully elevated lead level needs a source investigation, not just a supplement response.
Read the studies on Lead