Iron

Common forms: Ferrous Bisglycinate Chelate · Ferrous Sulfate · Ferrous Fumarate

Recommended test

Ferritin, with Iron & TIBC

Ferritin reflects total body iron stores and is typically the earliest marker to drop as deficiency develops — it can flag a problem well before hemoglobin or standard "anemia" markers change. Serum iron alone fluctuates throughout the day and after meals, so it's unreliable on its own. Pairing ferritin with Total Iron Binding Capacity (TIBC) and transferrin saturation gives a fuller functional picture, since ferritin can also rise independently as an inflammation marker, which can mask a true deficiency.

Practice threshold: total (serum) iron ≤50 — supplementation is used here once serum iron is at or below this level, rather than ferritin specifically.

Interpret all results with a healthcare provider — ferritin is also an acute-phase inflammatory marker, so a normal or even elevated result doesn't always rule out iron deficiency if inflammation is present at the same time.

Common forms & typical benefits

Which form, and why

Ferrous Bisglycinate Chelate

Iron bound to glycine amino acids, absorbed via peptide transporters rather than the standard iron pathway
Well tolerated with food; less affected by calcium, phytates, and other dietary inhibitors that block standard iron
The form used in Iron Bisglycinate and in HemeVite Plus (which pairs it with bovine liver extract and vitamin C as absorption cofactors)

Research noteA systematic review of 17 RCTs (over 1,100 children and pregnant women) found ferrous bisglycinate achieved comparable or better ferritin and hemoglobin improvements than standard iron salts, at lower elemental doses, with significantly fewer GI side effects. A pilot RCT in anemic children found bisglycinate significantly increased ferritin where a comparison iron form did not, and absorption appeared self-regulated by the body's existing iron stores — the lower someone's starting ferritin, the more efficiently it was absorbed.

What the research says

Evidence by outcome

Outcome	Approx. evidence base	Typical finding
Ferritin / hemoglobin repletion (bisglycinate)	Systematic review, 17 RCTs (1,100+ people)	Comparable or better repletion vs. standard iron salts, at lower elemental doses
GI tolerability (bisglycinate vs. standard iron)	Same review + supporting trials	Significantly fewer GI side effects; better adherence over time
Ferritin response in children (bisglycinate vs. polymaltose iron)	Pilot RCT, anemic children	Bisglycinate significantly increased ferritin; comparison form did not

In practice, this is reached for specifically when someone's iron is too low to bring up through diet alone — not a default first step ahead of dietary correction.

Research summary chart

View PDF ↗

Dosages used in studies

What the research actually tested

Goal	Typical elemental dose	Common forms	Duration
Practitioner-used dose (this site)	25 mg/day, up to 25 mg 1-3x/day per label	Thorne Iron Bisglycinate / HemeVite Plus, standard label dosing	Ongoing, retest at 8-12 weeks
Confirmed deficiency repletion (research range)	25–36 mg (bisglycinate)	Ferrous bisglycinate	8–12+ weeks, then retest
Standard-form comparison dose (research range)	60–200 mg (ferrous sulfate)	Ferrous sulfate	8–12 weeks
Lower-dose / alternate-day approach (research range)	40–80 mg every other day	Various	8–12+ weeks

Note: bisglycinate's lower effective dose is a function of better absorption, not a weaker product — check labels for elemental iron content specifically, since compound weight is higher.

Safety notes & high-dose risks

What to watch for

Don't supplement iron without a confirmed deficiency — unlike magnesium, iron doesn't have a simple built-in excretion mechanism, so unnecessary supplementation can actually build up in the body over time.
Common side effects: constipation, nausea, dark stools — bisglycinate forms tend to cause these less often than standard iron salts.
Higher-risk groups: anyone with hemochromatosis or other iron-overload conditions should not supplement iron without direct medical supervision.
Serious risk — accidental overdose in children: iron-containing supplements are a leading cause of fatal accidental poisoning in young children. Keep all iron products well out of reach.

Additional notes

Worth knowing

Absorption tips: avoid taking with calcium/dairy at the same time, which competes for absorption; vitamin C alongside iron (as in HemeVite Plus) improves uptake.
Medication interactions: can reduce absorption of certain antibiotics and thyroid medication if taken together — space these doses apart.
Extra caution: anyone with a history of iron overload, hemochromatosis, or GI conditions like ulcerative colitis.
More is not better: once serum iron is repleted, continuing high-dose supplementation isn't protective and can contribute to overload over time.
Retesting: serum iron (the practice threshold used here), alongside ferritin and the full iron panel, roughly every 8-12 weeks after starting supplementation is a reasonable check-in point.
Form and quality matter: standard ferrous sulfate is cheap but often poorly tolerated long-term; a chelated form is usually worth the cost difference for adherence.

Shop on Fullscript Shop on Prodrome

Educational information only — not medical advice. Lab testing and any supplementation decisions should be made with a qualified healthcare provider who knows your personal health history. Research findings vary by population, dose, form, and study quality.

Some links go to Fullscript, where I may earn a commission at no extra cost to you. I only recommend supplements I've either used myself or seen work in my clients' lab data. Results vary from person to person.