Forms of iron compared
Iron in a supplement is always part of a compound, and the share of iron in that compound varies. The NIH Office of Dietary Supplements gives ferrous fumarate as 33% elemental iron by weight, ferrous sulfate as 20% and ferrous gluconate as 12%. The label states the elemental iron, so you do not have to calculate it.
| Form | What it is | Iron per dose on our labels |
|---|---|---|
| Iron bisglycinate (Ferrochel) | iron bound to two glycine molecules, an amino acid chelate | 18 mg or 36 mg |
| Ferrous fumarate | iron salt of fumaric acid, 33% iron | 18 mg |
| Iron citrate | iron salt of citric acid | 25 mg |
The EU health claims apply to iron in any of these forms. What differs between products is the amount of iron, the directions and the price per day.
Reading the dose
The EU NRV for iron is 14 mg.
| Iron per dose | % of NRV (14 mg) |
|---|---|
| 18 mg | 128% |
| 25 mg | 179% |
| 36 mg | 257% |
Read the directions as well as the number. One of our 36 mg products is meant to be taken every other day, so its daily average is half the label figure. Keep that in mind when you compare prices per day.
Haem and non-haem iron
NIH ODS describes two kinds of iron in food. Haem iron comes from meat, poultry and seafood. Non-haem iron is found in plant foods and in fortified foods, and it is the kind used in supplements. The body absorbs haem iron more readily, which is why the way you take a supplement matters.
Price per day and pack size
We calculate the price per day from the directions on the label. For a product taken every other day, a pack of 60 capsules, for example, covers 120 days, so its price per day is half of what the capsule count suggests. Compare the price per day rather than the pack price.
What affects iron absorption
Supplements contain non-haem iron, the same type as in plant foods. NIH ODS describes what changes how much of it is absorbed:
- vitamin C taken at the same meal increases absorption of non-haem iron;
- phytates in grains and beans, and some polyphenols, reduce it;
- calcium may interfere with iron absorption, although this has not been firmly established;
- supplements with 25 mg of iron or more, taken at the same time as zinc, can reduce zinc absorption.
If you take calcium or zinc as well, it is simplest to take them at a different time of day from the iron. Our zinc supplements show the zinc per dose, so you can see how much you take.
EU health claims for iron
Regulation (EU) No 432/2012 permits these statements for products that provide at least 15% of the NRV per daily dose:
- Iron contributes to normal formation of red blood cells and haemoglobin.
- Iron contributes to normal oxygen transport in the body.
- Iron contributes to the reduction of tiredness and fatigue.
Questions
Which iron supplement should I choose?
Compare the iron per daily dose, the directions on the label and the price per day. Bisglycinate, fumarate and citrate all carry the same EU claims, so the form alone does not decide it.
When should I take iron?
Follow the directions on the label. Keep iron apart from calcium and zinc supplements, and take it with a drink or meal that contains vitamin C if that suits you. If your product is the every-other-day one, mark the days so you do not take it two days running.
How much iron a day is too much?
The EU NRV is 14 mg. NIH ODS gives 45 mg a day as the upper limit for adults, counting iron from every source. Add the iron in any multivitamin you take and keep to the daily doses on the labels.
Can I take iron with other supplements?
Yes, but count the iron in any multivitamin you take and keep to the daily doses on the labels. Take calcium and zinc at a different time from iron; vitamin C can go with it.
Do vegetarians need more iron?
NIH ODS states that the recommended intakes for vegetarians are 1.8 times higher than for people who eat meat, because non-haem iron from plants is absorbed less well. If you avoid animal products, also check whether the capsule shell is gelatin.
How should I store iron supplements?
Follow the storage text on the label and keep the pack out of reach of children. NIH ODS warns that accidentally swallowed iron supplements are especially dangerous for young children.
Sources
- Regulation (EU) No 1169/2011, Annex XIII (reference intakes)
- Regulation (EU) No 432/2012 (permitted health claims)
- NIH Office of Dietary Supplements: Iron fact sheet
- NIH Office of Dietary Supplements: Zinc fact sheet
- EFSA: Health claims
Content reviewed by Inese Kalniņa, dietitian.
2026-09-04
