Iron Bisglycinate: Benefits, Dosing & Tolerability
Also known as: ferrous bisglycinate, chelated iron, gentle iron, iron glycinate
Iron bisglycinate (ferrous bisglycinate) is a 'chelated' form of iron in which the mineral is bound to the amino acid glycine, which makes it well absorbed and typically gentler on the stomach than older forms like ferrous sulfate. It's often chosen by people who need iron for iron-deficiency or iron-deficiency anemia but couldn't tolerate the constipation and nausea of standard iron. Absorption improves with vitamin C and on a relatively empty stomach, and is reduced by calcium, coffee, and tea taken at the same time. Because too much iron is harmful, it should generally be taken to correct a confirmed deficiency rather than routinely — ideally guided by blood tests.
Iron bisglycinate at a glance
| What it is | Chelated iron (iron + glycine)A well-absorbed form often marketed as 'gentle iron'. |
| Typical dose | ~14–28 mg elemental iron/dayDeficiency dosing varies; follow your clinician and lab results. |
| Best taken with | Vitamin C, empty-ish stomachVitamin C (or a glass of orange juice) boosts absorption. |
| Avoid taking with | Calcium, coffee, tea, dairyThese reduce iron absorption — separate by ~2 hours. |
| Tolerability | Usually gentler than sulfateLess constipation/nausea for many people. |
Elemental iron is what counts — check the label. Iron needs and dosing should be based on blood tests and clinician guidance.
Why people choose iron bisglycinate
- Well absorbed thanks to its chelated (glycine-bound) structure, which is protected from some absorption inhibitors.
- Typically gentler on the gut than ferrous sulfate, with less constipation, nausea, and cramping.
- Useful for treating iron deficiency and iron-deficiency anemia, especially in people who couldn't tolerate other forms.
- Often better tolerated during pregnancy or heavy menstrual periods, when iron needs rise (use under medical guidance).
- May be effective at lower elemental doses because of good absorption, which can further reduce side effects.
Dosing and timing
- Take the elemental iron dose your clinician recommends based on your labs — don't guess, since needs vary a lot.
- Pair it with vitamin C (a supplement or a glass of orange juice) to boost absorption.
- Take it away from calcium supplements, dairy, coffee, and tea — separate these by about 2 hours.
- A relatively empty stomach absorbs iron best, but taking it with a little food is fine if it causes nausea.
- Emerging evidence suggests every-other-day dosing may absorb as well as daily dosing for some people — ask your clinician.
- Recheck iron studies (ferritin, etc.) with your doctor to confirm you're replenishing stores and to know when to stop.
Side effects and cautions
- Iron can still cause constipation, dark stools, or stomach upset, even in gentler forms — dark stools are expected and harmless.
- Don't take iron without a reason: excess iron is harmful, and conditions like hemochromatosis make supplementing dangerous.
- Iron overdose is a leading cause of poisoning in children — keep it well out of reach.
- Iron reduces absorption of some medications (levothyroxine, certain antibiotics) — separate the doses.
- Persistent fatigue or suspected anemia should be evaluated with blood tests rather than self-treated, since the cause matters.
Is Iron Bisglycinate right for you?
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Frequently asked questions
Is iron bisglycinate better than ferrous sulfate?
Iron bisglycinate is a chelated form that's well absorbed and usually gentler on the stomach, so many people who get constipation or nausea from ferrous sulfate tolerate it better. Both can correct iron deficiency; bisglycinate's main advantage is tolerability, which helps people actually stick with treatment.
When is the best time to take iron bisglycinate?
Iron absorbs best on a relatively empty stomach and alongside vitamin C (such as orange juice). Take it away from calcium supplements, dairy, coffee, and tea — ideally separated by about 2 hours — since those reduce absorption. If it upsets your stomach, a little food is acceptable.
Does iron bisglycinate cause constipation?
It can, but generally less than older forms like ferrous sulfate. Dark stools are a normal, harmless effect of iron. Staying hydrated, eating fiber, and (with your clinician's okay) trying every-other-day dosing can help with tolerability.
Should I take iron without a blood test?
Generally no. Because excess iron is harmful and some people accumulate too much (as in hemochromatosis), iron supplements should be used to correct a confirmed deficiency, guided by blood tests and a clinician — not taken routinely just for fatigue.
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Medically reviewed by Antonieta Rueda, MD and Kyle R. Toth, MD · Last reviewed July 6, 2026
This article is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Dietary supplements are not regulated like medications, quality varies between products, and they can interact with prescription drugs and existing conditions. Talk to your doctor or pharmacist before starting any supplement, especially if you are pregnant, nursing, have a medical condition, or take other medications.