Iron wrapped in two amino acid molecules. Raises blood and stored iron at least as well as older iron tablets, at roughly half the iron dose, with markedly fewer digestive complaints. Benefit is confined to those genuinely depleted; higher lifelong iron levels track with shorter life expectancy. The cleanest trials confirmed depletion first, dosed minimally, and stopped once stores filled. (Full Review)

Protocol

Standard repletion dose

25–30 mg elemental iron

25 mg matched 50 mg of ferrous sulfate for prophylaxis in a randomized pregnancy trial.

Alternate-day scheduling

Every second day

Equal ferritin, fewer complaints, and less deficiency at six months in a randomized trial.

Best time of day

Morning, empty stomach

Or 1 hour before food. Hepcidin rises through the day, so later doses are absorbed less efficiently.

Time to effect

Hemoglobin

3–4 weeks

Young red cells rise within 7–10 days; hemoglobin recovers before stores do.

Ferritin and symptom relief

8–12 weeks

The point at which ferritin and transferrin saturation are rechecked.

Full store repletion

3–6 months

A corrective course rather than an indefinite daily supplement.

Benefits

High: Correction of iron-deficiency anemia; replenishment of body iron stores; lower gastrointestinal adverse-event burden than conventional iron salts; reduction of fatigue in iron deficiency without anemia

Medium: Preserved absorption from plant-rich and inhibitor-heavy meals; improvement of restless legs syndrome symptoms

Low: Exercise capacity and aerobic performance; cognitive performance and mood in iron deficiency without anemia

Speculative: Favourable intestinal redox and bile-acid signalling; support of iron-dependent mitochondrial enzymes in later life

Contraindications

Hereditary hemochromatosis (HFE C282Y homozygotes, compound heterozygotes), even with normal iron indices

Transfusion-dependent thalassemia, sideroblastic anemia, myelodysplastic syndrome with iron loading

Transferrin saturation above 45%, or ferritin above 300 µg/L (men) or 200 µg/L (women), without documented deficiency

Porphyria cutanea tarda and erythropoietic protoporphyria

Active untreated peptic ulcer or unevaluated gastrointestinal bleed

Anemia not established as iron-deficient (chronic disease, B12 or folate deficiency)

Children under 6 in the household without child-resistant storage

Concurrent iron chelators (deferoxamine, deferasirox)

Therapeutic phlebotomy for iron overload

Key Interactions

Levothyroxine (thyroid hormone replacement)

Tetracyclines and fluoroquinolones (doxycycline, minocycline, ciprofloxacin, levofloxacin)

Bisphosphonates (alendronate, risedronate), levodopa, methyldopa

Proton pump inhibitors and H2 blockers (omeprazole, famotidine)

Mycophenolate, penicillamine, and integrase inhibitors (dolutegravir, raltegravir)

Calcium and zinc supplements

Vitamin C (ascorbic acid); additive

Lactoferrin, heme iron polypeptide, iron-containing multivitamins; additive

Blood donation

Risk & Side Effects

High: Gastrointestinal adverse effects; acute toxicity after accidental overdose

Medium: Iron accumulation in genetically susceptible individuals; reduced absorption of co-administered medication; black stools masking gastrointestinal bleeding

Low: Higher iron status and long-term cardiometabolic and lifespan signals; iron supplementation in infection-prone settings; elevated serum ferritin without corresponding iron excess

Speculative: Expansion of Enterobacteriaceae in the gut microbiome; ferroptosis and oxidative tissue injury from chronic iron excess

Monitoring

Marker	Target	Why
Ferritin	50–100 ng/mL (women); 50–150 ng/mL (men)	Best single index of total body iron stores
Transferrin saturation	25–35%	Iron available for delivery to tissues; the earliest overload signal
Hemoglobin	13.0–15.0 g/dL (women); 14.0–16.0 g/dL (men)	Confirms whether deficiency has progressed to anemia and tracks response
MCV and RDW	MCV 85–92 fL; RDW below 13%	Early morphological signature of iron deficiency; RDW rises before MCV falls
Soluble transferrin receptor	Within the assay's stated reference interval, toward the lower half	Reflects tissue iron demand and, unlike ferritin, is not raised by inflammation
High-sensitivity C-reactive protein	Below 1.0 mg/L	Determines whether a ferritin value is trustworthy
ALT	Below 25 U/L (men); below 20 U/L (women)	Detects hepatic injury from iron accumulation
HbA1c	Below 5.4%	Iron loading impairs beta-cell function, tracking the metabolic consequence of excess
HFE genotype (C282Y and H63D)	No numeric range; track the paired transferrin saturation trend	Identifies the small group at high risk of iron loading before any supplementation begins

Cadence: Baseline panel before starting; ferritin and complete blood count at 8 and 12 weeks, then every 3–6 months while supplementation continues, dropping to every 6–12 months on maintenance. HFE genotype is a one-time test.

Qualitative Assessment

Daytime fatigue and exercise recovery, scored weekly on a consistent scale
Cold intolerance, particularly in the hands and feet
Restless legs symptoms and the number of night-time awakenings
Cognitive clarity and short-term memory during demanding work
Exercise capacity at a fixed workload, such as heart rate at a habitual pace
Hair shedding, brittle nails, and paleness of the inner eyelid
Pica (craving non-food substances such as ice or clay)
Gastrointestinal comfort and stool consistency on the current dose

Ferrous Bisglycinate for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment