Iron supplements compared: Which is the best?

Iron is an essential trace element that the body needs for oxygen transport, energy production, and the immune system. A deficiency can lead to symptoms such as fatigue, concentration problems, or hair loss. Women, in particular, often suffer from this and try to meet their needs with iron supplements.

But which iron supplement is right for you? There's a wide selection, but not all products are equally well-tolerated and effective. Here, you'll learn about the different types of iron supplements available, what to look for when choosing, and how you can optimize your iron absorption.

Here you will find out...

What iron products are available? What should I look for in an iron supplement? Conclusion

The most important things in brief

Bioavailability & Tolerability : Iron(II) compounds such as iron bisglycinate are better absorbed and are gentler on the stomach.

Combination with vitamin C : Promotes iron absorption and improves effectiveness.

Fewer side effects : Stomach-friendly additives such as lactoferrin reduce symptoms such as nausea or constipation.

What iron products are there?

Which dosage form is best for you depends on various factors such as tolerability, the amount required and your personal needs.

You can find an overview of the most common variants here:

Tablets

Most common form of iron supplements
Usually contains iron(II) sulfate or iron(III) gluconate
Often high doses
May cause gastrointestinal discomfort

Capsules

Better tolerated than tablets
Often with vitamin C or lactoferrin for better absorption
Stomach-friendly coating possible

Liquid iron supplements

Ideal for people with swallowing problems
Easy to dose, but often lower concentration
Longer intake period necessary

Iron infusions

Fast effect in cases of severe iron deficiency
Only administered by a doctor
More expensive and associated with risks such as allergic reactions [1]

Natural sources of iron

Contains iron from spirulina, plant extracts or meat concentrates
Gentle on the stomach, but often lower dosage [2,3]

Are you suffering from iron deficiency and looking for a tolerable solution? The FemBe Iron & Lactoferrin - Be3 Iron Formula offers a stomach-friendly combination of highly bioavailable iron bisglycinate, natural vitamin C from rose hips, and bioactive lactoferrin. Perfect for gently and effectively replenishing your iron stores – without the typical side effects of conventional iron supplements.

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The perfect iron supplement

Here are some things to look for when looking for a high-quality iron supplement:

1. High bioavailability

Bioavailability describes how well the body can absorb and utilize a substance. Iron in its divalent form, 'iron(II),' is better absorbed by the body than its trivalent form, 'iron(III).' Organic compounds such as iron bisglycinate or iron fumarate are particularly bioavailable and, at the same time, more gentle on the stomach than inorganic compounds [4].

2. Combination with vitamin C

Vitamin C improves iron absorption. A good iron supplement therefore often contains ascorbic acid. Alternatively , vitamin C-rich foods such as orange juice or a piece of bell pepper should be consumed [5].

3. Gentle on the stomach composition

Gentle-on-the-stomach supplements such as lactoferrin or special tablet coatings can help prevent stomach upset or constipation. Lactoferrin , a milk protein, promotes iron absorption and also has anti-inflammatory properties. This makes the iron supplement gentler on the stomach and even more effective [6].

4. Free from unnecessary additives

The perfect iron supplement should not contain unnecessary fillers, preservatives or dyes that can cause allergies or intolerances [7].

5. Flexible dosage

Particularly practical are preparations with different dosage options , which can be used both preventively and in cases of acute iron deficiency . This allows you to tailor the dosage to your individual needs.

Conclusion

Iron is essential for the body, but not every supplement will provide the desired effect. To ensure you replenish your iron levels in a targeted manner, the right supplement should be highly bioavailable, well-tolerated, and free of unnecessary additives. Iron bisglycinate or iron fumarate have proven particularly effective—ideally combined with vitamin C for optimal absorption.

💡 Tip: Compare different products and find the iron supplement that best suits your body and needs!

How do I recognize a high-quality iron supplement?

A good iron supplement should:
✔ Contain highly bioavailable iron (e.g. ferrous bisglycinate or ferrous fumarate).
✔ Combined with vitamin C to improve iron absorption.
✔ Be gentle on the stomach , e.g. with lactoferrin or a special coating.
✔ Be free from unnecessary additives such as preservatives or artificial colors.
✔ Offer flexible dosage options depending on individual needs.

Why should iron be combined with vitamin C?

Vitamin C significantly improves iron absorption in the intestine by converting trivalent iron (Fe³⁺) into the more easily absorbed divalent form (Fe²⁺). Therefore, iron should ideally be taken with vitamin C-containing foods such as orange juice or a vitamin C supplement.

What side effects can iron supplements have?

Common side effects include:
- Gastrointestinal complaints (nausea, abdominal pain)
- Constipation or diarrhea
- Dark discoloration of the stool (harmless)
- Metallic taste in the mouth

Tip: Forms of iron that are gentle on the stomach, such as iron bisglycinate or iron in combination with lactoferrin, are often better tolerated.

How long should you take iron supplements?

The duration depends on the iron deficiency:
For mild deficiency: 1–3 months
In case of severe deficiency: 3–6 months (or after consultation with a doctor)
Preventive for risk groups (pregnant women, vegans): long-term in low dosage

Important: Checking the ferritin level (storage iron) helps to determine the optimal duration of use.

Why shouldn't iron be taken with coffee or milk?

Coffee, tea, and milk contain inhibitors such as tannins, polyphenols, and calcium , which significantly reduce iron absorption in the intestines. Therefore, iron should be taken with water or juice , and at least 1–2 hours apart from coffee, tea, or milk.

References for further reading:

Bloor SR, Schutte R, Hobson AR. Oral Iron Supplementation—Gastrointestinal Side Effects and the Impact on the Gut Microbiota. Microbiology Research 2021; 12(2):491–502. doi: 10.3390/microbiolres12020033.
Cotoraci C, Ciceu A, Sasu A, Hermenean A. Natural Antioxidants in Anemia Treatment. Int J Mol Sci 2021; 22(4). doi: 10.3390/ijms22041883.
Janda-Milczarek K, Szymczykowska K, Jakubczyk K, Kupnicka P, Skonieczna-Żydecka K, Pilarczyk B et al. Spirulina Supplements as a Source of Mineral Nutrients in the Daily Diet. Applied Sciences 2023; 13(2):1011. doi: 10.3390/app13021011.
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(8):904–20. doi: 10.1093/nutrit/nuac106.
Piskin E, Cianciosi D, Gulec S, Tomas M, Capanoglu E. Iron Absorption: Factors, Limitations, and Improvement Methods. ACS Omega 2022; 7(24):20441–56. doi: 10.1021/acsomega.2c01833.
Zhao X, Zhang Nutrients 2022; 14(3). doi: 10.3390/nu14030543.
Lloyd I. Excipients and Fillers - Health Facts; 2013 [as of February 4, 2025]. Available at: https://www.ndhealthfacts.org/wiki/Excipients_and_Fillers.