Iron Bisglycinate: Uses, Benefits, Dosage & Safety
Last updated: August 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy
Quick summary
Iron bisglycinate is chelated iron with markedly better tolerability than ferrous sulphate — far less constipation and nausea — at comparable absorption. It is the form worth trying if standard iron has defeated you.
What is Iron Bisglycinate?
Iron chelated to two glycine molecules. The chelate is absorbed through amino acid transport routes rather than the standard ferrous iron pathway, which reduces free iron in the gut and therefore the irritation and oxidative effects that cause most iron side effects.
What Iron Bisglycinate is commonly used for
Iron deficiency and iron deficiency anaemia, pregnancy supplementation, and iron repletion in anyone who cannot tolerate ferrous sulphate.
How Iron Bisglycinate works
Absorbed iron is incorporated into haemoglobin, myoglobin and iron-dependent enzymes. The bisglycinate advantage is entirely about the absorption route: less unabsorbed free iron in the gut lumen means less irritation, less constipation, and less of the gut microbiome disruption that high-dose ferrous salts cause.
What the evidence says
Each claim below is tied to the specific study behind it, rather than to a general reading list.
- Iron bisglycinate showed better tolerability than ferrous sulphate at comparable efficacy. Name et al., Frontiers in Nutrition, 2018 — comparative clinical study. (PubMed)
- Alternate-day iron dosing improves fractional absorption by lowering hepcidin. Stoffel et al., Lancet Haematology, 2017 — randomised controlled trial. (PMID 29032957)
- Chelated iron produces less gastrointestinal irritation than ferrous salts. Comparative iron tolerability literature. (PubMed)
Typical dosage used in studies
25–50 mg elemental iron daily is typical, less than the 65 mg+ of ferrous sulphate regimens. Alternate-day dosing improves fractional absorption by reducing hepcidin response — a genuinely useful and underused finding. Vitamin C improves absorption.
Side effects and safety
Much better tolerated than ferrous salts. The important rule is not to supplement iron without a confirmed deficiency — iron overload damages liver, heart and pancreas, and haemochromatosis is common. Iron tablets are also a leading cause of fatal poisoning in young children.
Medication interactions and who should avoid Iron Bisglycinate
Medication & safety check
Reduces absorption of levothyroxine, quinolone and tetracycline antibiotics, bisphosphonates and levodopa — separate by two hours. Calcium, tea, coffee and PPIs reduce iron absorption; vitamin C improves it. Never supplement in haemochromatosis.
General information, not personal medical advice. If you take any medication, confirm it is safe to combine with Iron Bisglycinate with your doctor or pharmacist first.
Sources & further reading
The claim-level citations above are drawn from these sources:
- Name et al., Frontiers in Nutrition, 2018 — comparative clinical study — find on PubMed
- Stoffel et al., Lancet Haematology, 2017 — randomised controlled trial — PMID 29032957
- Comparative iron tolerability literature — find on PubMed
- NIH Office of Dietary Supplements
- NIH National Center for Complementary and Integrative Health
Frequently asked questions
Should I take iron every day?
Alternate-day dosing may absorb better, because daily dosing raises hepcidin which blocks the next dose. Discuss it with whoever is managing your deficiency.
Do I need a blood test first?
Yes. Ferritin and full blood count. Supplementing iron without deficiency risks overload, which causes real organ damage.
Why does regular iron constipate me?
Unabsorbed ferrous iron irritates the gut lining and disrupts the microbiome. Bisglycinate leaves much less free iron behind.
Part of a wider guide
Iron Bisglycinate is one form of Iron. This page covers what is specific to this form — absorption, tolerability, dosing and who it suits. For the underlying nutrient itself, its overall evidence base and general safety, read the Iron guide.
Where you'll find Iron Bisglycinate
Iron Bisglycinate appears in Minerals & Anaemia formulas. Browse the supplement guides to see the products we review, each with a full breakdown of formula, pricing and safety.
Related ingredients to explore
Ingredients often studied or formulated alongside Iron Bisglycinate.
General information, not medical advice.