What Is Iron Bisglycinate? Identity, Source and Supplement Use

1. Direct 40–80 word answer

Iron bisglycinate, also called ferrous bisglycinate, is a form of iron in which one iron (II) ion is bound to two glycine molecules, forming a stable ring-shaped compound called a chelate. Manufacturers make it by reacting an iron source with glycine, and it is used in supplements and fortified foods as a source of elemental iron. It is often marketed as gentle on the stomach, but the evidence for that claim is still limited.

2. Key facts box

Key fact	Detail
Common names	Iron bisglycinate; ferrous bisglycinate; iron bisglycinate chelate
Category	Mineral supplement ingredient; amino acid chelate of iron
Chemical makeup	One iron (II) ion bound to two glycine molecules (formula C4H8FeN2O4)
Elemental iron content	About 27% in the pure compound; commercial ingredients often about 20%; use the label figure
Source	Manufactured from an iron source and glycine; not a plant extract
Typical forms	Capsules, tablets, powders, liquid drops, chewables, gummies, multivitamins and prenatal products
Why it is used	Source of non-heme iron; marketed as gentle on the stomach
Evidence summary	Some trials show effectiveness at lower doses; overall certainty is low to moderate
Reference intakes	RDA 8 mg (men), 18 mg (women 19 to 50); adult upper limit 45 mg per day
Key caution	Not for people with iron overload; dangerous in overdose, especially for children

 

This summary is educational and is not medical advice. Whether you need iron, and how much, should be decided with a health professional.

3. Scientific/common names

The most precise name is ferrous bisglycinate, which tells you three things. "Ferrous" means the iron is in the iron (II) state. "Bis" means two. "Glycinate" means glycine that has bound to the metal. The same compound appears on labels under several names.

•      Ferrous bisglycinate or ferrous bis-glycinate: the standard chemical and regulatory name.

•      Iron bisglycinate: the common supplement name, used on most consumer labels.

•      Ferrous bisglycinate chelate or iron bisglycinate chelate: names that emphasize the chelated structure.

•      Iron glycinate or ferrous glycinate: shorter names that are sometimes used for the same compound, although labels should be read carefully because the term is not always applied consistently.

•      Iron amino acid chelate: a broader term for iron bound to amino acids, which can describe bisglycinate but can also describe other products.

Some versions are sold under trademarked brand names. A brand name is a marketing label, not a different chemical, though the manufacturing process and specifications may differ between suppliers. The chemical formula of the pure compound is C4H8FeN2O4, with a molecular weight of about 204.

4. Ingredient category

Iron bisglycinate is a mineral supplement ingredient, specifically an amino acid chelate of a mineral. In nutrition terms, it is a source of the essential mineral iron. It is not a vitamin, an herb or a hormone, and it is not a drug in its use as a nutrient.

Within the family of iron supplements, bisglycinate belongs to the chelated forms, in contrast to simple iron salts such as ferrous sulfate, ferrous fumarate and ferrous gluconate. A chelate is a structure in which a metal ion is held by a molecule that grips it at more than one point. In bisglycinate, each glycine molecule attaches to the iron through its nitrogen and oxygen atoms, forming two five-membered rings around a single iron ion.

Regulators treat it as an approved mineral source in many places. In the European Union, ferrous bisglycinate is listed among the permitted iron sources for food supplements and food fortification under the supplements directive and its amendments. In other countries, it is used as a dietary ingredient and a food fortificant, with rules that vary. Buyers should check the regulations in their own country.

5. Natural source / plant part / nutrient form

Iron bisglycinate does not come from a plant part. It is not a botanical extract, and it is not a compound that people eat as such in food. Foods contain iron in two main forms: heme iron in meat, fish and poultry, and non-heme iron in plants, eggs, dairy and fortified foods. Iron bisglycinate is a manufactured nutrient form that is used as a non-heme iron source.

Its two building blocks both exist in nature. Iron is a mineral found throughout the earth's crust, and glycine is the simplest amino acid, present in all dietary proteins. What does not occur in food is the specific iron bisglycinate chelate, which is made under controlled conditions.

6. Where it comes from

Iron bisglycinate is produced industrially. In general terms, an iron source, such as a ferrous salt or iron compound, is reacted with glycine in water under controlled conditions. The iron binds to glycine to form the chelate, and the product is purified, dried and milled into a powder. The exact method and the iron source vary between manufacturers.

Glycine itself can be produced by chemical synthesis or obtained from protein hydrolysis or fermentation. The source of glycine is rarely stated on the label, which is why people who avoid animal-derived ingredients may need to ask the manufacturer.

7. How it is used in supplements

Iron bisglycinate is used as a source of elemental iron in supplements designed to supply or replenish iron. Manufacturers use it in stand-alone iron supplements, multivitamins, prenatal products, children's formulas and fortified foods and drinks.

The main reason it is chosen is tolerability. Standard iron salts cause stomach upset in many people, and chelated forms are marketed as gentler. A second reason is that the chelate may be protected from some inhibitors of absorption in the gut, such as phytate from grains and legumes. This may help explain why some studies find similar results with a lower iron dose, although the mechanism is not fully established.

In practice, label doses for bisglycinate products often fall in the range of about 18 to 30 mg of elemental iron per serving, though both lower and higher doses exist. What matters is the elemental iron per serving and not the total weight of the bisglycinate compound. A pure ferrous bisglycinate molecule is about 27% iron by weight, and commercial ingredients are often specified at a lower figure, around 20%, so always rely on the label's elemental iron amount.

8. Main active constituents

The active constituent of iron bisglycinate is elemental iron in the ferrous state. This is the nutrient that the body uses to build hemoglobin, transport oxygen and support enzymes involved in energy metabolism.

The glycine portion acts as a carrier. It makes up roughly 70% of the weight of the pure compound, but at typical supplement doses it adds only tens of milligrams of glycine, far below the grams used in glycine supplements. It is not considered the active ingredient in this context.

9. Why people research it

People look up iron bisglycinate mostly for one reason: they want an iron supplement that is effective and easy on the stomach. Several groups raise this question, including pregnant women, people with heavy menstrual bleeding, vegetarians and vegans, athletes, and people who stopped taking iron because of side effects.

The research is encouraging but not conclusive. In a randomized trial in pregnant women in Denmark, 25 mg of iron as ferrous bisglycinate was as effective as 50 mg of iron as ferrous sulfate for preventing iron deficiency and anemia, with fewer gastrointestinal complaints. A study in infants and young children reported that ferrous bisglycinate was effective in treating iron-deficiency anemia. A 2023 systematic review of randomized trials in adults and children found that bisglycinate improved hemoglobin and ferritin, often at lower elemental doses, but it rated the certainty of the evidence as low because of study quality and differences between trials.

Absorption studies add some mechanistic support. Research using labeled iron suggests that absorption from bisglycinate responds to a person's iron status, which is a desirable property, and may be less affected by phytate than that of ferrous sulfate. However, most evidence comes from small studies, many used ferrous sulfate as the only comparator, and some trials were funded by companies with an interest in the ingredient. For these reasons, it is fair to say that bisglycinate is a well-studied alternative, not a proven superior form.

10. Common supplement forms

Iron bisglycinate is sold in a variety of formats. The best format depends on the person's needs, preferences and age, and on the quality of the manufacturer.

Form	Typical use	Buyer notes
Capsules	Everyday supplementation	Check the elemental iron and the capsule material
Tablets	Higher-dose or low-cost products	Look for evidence of proper disintegration
Powder	Mixing into drinks or food	Taste and accurate measuring matter
Liquid drops or syrups	Infants, children, people who struggle with pills	Needs exact dosing and secure child-resistant storage
Chewables and gummies	Children and adults who prefer them	Can look like sweets; store out of reach; check iron per serving
Multivitamins and prenatals	Broad nutrient coverage	Other minerals, such as calcium, may reduce iron absorption

 

Whatever the format, the key checks are the same: the label states elemental iron per serving, the form is named, the product has testing documents, and the other ingredients are acceptable to the buyer.

11. What it is not / common confusion

•      It is not the same as ferrous sulfate. Ferrous sulfate is a simple iron salt and the most studied form. Bisglycinate is a chelate. They contain different amounts of iron per tablet weight.

•      It is not "iron glycinate" in every case. Some labels use the term loosely, so the full name on the supplement facts panel is the safest reference.

•      It is not heme iron. Heme iron comes from animal blood or tissue and is absorbed by a different pathway.

•      It is not a plant extract or a "natural" food iron. It is a manufactured mineral form.

•      It is not guaranteed to be free of side effects. Constipation, nausea and dark stools still occur in some people.

•      It is not a treatment for anemia on its own. Anemia has many causes and needs diagnosis.

•      It is not exempt from dose limits. Chelation does not change the 45 mg adult tolerable upper intake level.

12. Safety note

Iron bisglycinate carries the same core safety considerations as other iron supplements. The recommended dietary allowance is 8 mg per day for adult men and 18 mg per day for women aged 19 to 50, and the adult tolerable upper intake level is 45 mg per day. Doses used in trials to treat deficiency are often higher and were given under supervision.

•      Overdose in children: Iron is a leading cause of fatal poisoning in young children. Keep all iron products, including chewables and gummies, locked away. In case of ingestion, call a poison center or emergency service immediately.

•      Iron overload: People with hemochromatosis or other iron-overload conditions should not take iron unless a clinician directs it.

•      Unexplained deficiency: Low iron can signal blood loss or another condition, so it should be investigated and not just treated.

•      Medicine interactions: Iron can reduce the absorption of some medicines, including levothyroxine and certain antibiotics, and calcium, tea, coffee and some acid-reducing medicines can reduce iron absorption.

•      Pregnancy and breastfeeding: Iron needs change, and dosing should follow professional advice.

•      Side effects: Nausea, constipation, diarrhea, stomach pain and dark stools can occur. Severe pain, vomiting blood or black tarry stool needs urgent care.

This page is not medical advice. Speak with a doctor or pharmacist before taking iron, especially if you take prescription medicines, are pregnant or have a medical condition.

13. FAQ

Is iron bisglycinate better absorbed than ferrous sulfate?

Some studies show similar or better results at lower doses, but the evidence is limited and often low certainty. Ferrous sulfate remains the best-studied form.

Does iron bisglycinate cause less constipation?

It may cause fewer stomach complaints in some people, based on trials and reviews, but individual responses vary and side effects can still occur.

Is iron bisglycinate vegan?

It is usually made synthetically, so it may be suitable, but the glycine source and the capsule or other ingredients should be confirmed with the manufacturer.

How much iron does iron bisglycinate contain?

The pure compound is about 27% iron by weight, and commercial ingredients are often around 20%. Always use the elemental iron figure on the label.

Can I take iron bisglycinate with food?

Food reduces absorption of most non-heme iron but may lessen stomach upset. Tea, coffee and calcium reduce absorption, and vitamin C can help. Timing advice should come from your clinician.

14. References

1.      Hertrampf E, Olivares M. Iron amino acid chelates. Int J Vitam Nutr Res. 2004;74:435-443.

2.      Milman N, Jønsson L, Dyre P, Pedersen PL, Larsen LG. Ferrous bisglycinate 25 mg iron is as effective as ferrous sulfate 50 mg iron in the prophylaxis of iron deficiency and anemia during pregnancy in a randomized trial. J Perinat Med. 2014;42:197-206.

3.      Pineda O, Ashmead HD. Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate. Nutrition. 2001;17:381-384.

4.      Jeppsen RB, Borzelleca JF. Safety evaluation of ferrous bisglycinate chelate. Food Chem Toxicol. 1999;37:723-731.

5.      Bovell-Benjamin AC, Viteri FE, Allen LH. Iron absorption from ferrous bisglycinate and ferric trisglycinate in whole maize is regulated by iron status. Am J Clin Nutr. 2000;71:1563-1569.

6.      Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. Nutr Rev. 2023;81:904-920.

7.      Tolkien Z, Stecher L, Mander AP, Pereira DI, Powell JJ. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One. 2015;10:e0117383.

8.      Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397:233-248.

9.      Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academies Press; 2001.

10.   National Institutes of Health, Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. Bethesda, MD: NIH.

11.   European Parliament and Council. Directive 2002/46/EC on the approximation of the laws of the Member States relating to food supplements, as amended.

12.   National Center for Biotechnology Information. PubChem compound database: ferrous bisglycinate. Bethesda, MD: NCBI.