Iron Bisglycinate: Is It Better Than Ferrous Sulfate? 8 Facts Before You Buy
What Is Iron Bisglycinate?
Constipation and nausea are among the main reasons people stop taking iron tablets. That is why iron bisglycinate has become popular. It is ferrous iron bound to two molecules of the amino acid glycine in a chelated form. Here are 8 facts to help you understand this form, when it may suit you and when you should not take it at all.
1. How Iron Bisglycinate Differs From Other Forms
In the chelate, iron is shielded inside a glycine ring, so it reacts less in the gut with food components such as phytates. Small studies suggest it is well absorbed at lower doses of elemental iron and that many people find it gentler on the stomach. However, the trials are small, and what matters most is correcting a confirmed deficiency.
2. Comparing Iron Forms
| Form | Approx. elemental iron | Notes |
|---|---|---|
| Ferrous sulfate | 20% (higher in dried form) | Cheapest and best studied, but constipation and nausea are common |
| Ferrous fumarate | 33% | A lot of iron per tablet, with similar stomach effects to sulfate |
| Ferrous gluconate | 12% | Slightly milder but needs more tablets |
| Iron bisglycinate | 20% | Chelated, often better tolerated, less affected by food |
| Intravenous iron | Set by the doctor | Given in hospital for severe deficiency or poor absorption |
Always compare elemental iron rather than the weight of the salt. For example, 135 mg of iron bisglycinate provides 27 mg of elemental iron.
3. Confirm the Deficiency First
Feeling tired does not prove iron deficiency. Diagnosis needs a full blood count and ferritin, and sometimes transferrin saturation. Just as important is finding the cause, such as heavy periods, poor diet or hidden bleeding from the gut, which may need its own investigation.
4. Alternate-Day Dosing
After an iron dose, the hormone hepcidin rises for up to about a day and reduces absorption of the next dose. Studies have found that taking iron every other day can improve the fraction absorbed and reduce side effects in some people. Your doctor will choose the schedule that suits your levels and how quickly they need to rise.
5. What Blocks Absorption and What Helps
- Keep at least 2 hours between iron and tea, coffee, calcium, dairy and antacids.
- Keep at least 4 hours between iron and levothyroxine (thyroxine).
- Separate it from quinolone and tetracycline antibiotics as the antibiotic leaflet advises.
- Vitamin C or a glass of orange juice helps absorption.
6. Expected Side Effects
Dark or black stools are normal with any iron. Black, sticky stools with abdominal pain or dizziness, or vomiting blood, need urgent medical care. Constipation is usually less common with iron bisglycinate, but it can still happen, along with mild nausea or stomach discomfort.
7. Who Should Not Take Iron Bisglycinate Without a Doctor?
- People with hereditary haemochromatosis, because extra iron builds up in the liver and heart.
- People with thalassaemia or thalassaemia trait, whose small red cells may not reflect true iron deficiency.
- People who receive regular blood transfusions.
- Children: accidental iron overdose is a leading cause of fatal poisoning in children under 6, so keep tablets locked away.
8. Iron Bisglycinate in NOW Iron Complex
Each NOW Iron Complex tablet provides 27 mg of iron from 135 mg of iron bisglycinate (Ferrochel), with 50 mg vitamin C, 200 mcg folic acid, 50 mcg vitamin B12, 100 mg organic dong quai root and 100 mg red raspberry leaf. The dose is 1 tablet daily with a meal, for adults only. Because of the dong quai, it should not be used in pregnancy without a doctor, and it needs caution with warfarin because of a possible bleeding risk.
Since it contains folic acid, do not combine it with NOW Folic Acid 800 mcg without medical advice; read folic acid and vitamin B12. For a food-based option, see beef liver supplements and NOW Liver Caps. For the wider role of B vitamins, read B-complex benefits.
Frequently Asked Questions About Iron Bisglycinate
When does haemoglobin rise?
It usually starts rising within 2 to 4 weeks, and treatment typically continues for months to refill stores, guided by ferritin.
Should I take it on an empty stomach?
Absorption is higher on an empty stomach, but the product label says to take it with a meal, which is easier on the stomach.
Is it suitable in pregnancy?
Pregnant women need iron chosen by their doctor, and a herbal combination product should not be used without approval.
Can I double the dose to recover faster?
No. Higher doses raise side effects without a guaranteed benefit, and only your doctor should set the right iron bisglycinate dose based on ferritin and haemoglobin.
Is iron bisglycinate suitable for vegetarians?
NOW Iron Complex is labelled vegetarian and vegan, and plant-based diets often contain less absorbable iron, so a confirmed deficiency is common in this group.
Conclusion
Iron bisglycinate is a chelated form that is often better tolerated than ferrous sulfate, but it should only be taken for a deficiency confirmed by blood tests. Separate it from tea, calcium and thyroxine, consider alternate-day dosing with your doctor, and always store iron out of children’s reach. Find NOW Iron Complex at No Style Like Pharmacy.
This article was reviewed by the No Style Like pharmacy content team. It is for general awareness only and does not replace advice from your doctor or pharmacist.
Keep iron tablets away from children, and call emergency services at once if a child swallows any. For more information see the NIH Office of Dietary Supplements iron fact sheet.