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, difficulty concentrating, or hair loss. Women are particularly prone to this and often try to meet their needs with iron supplements.
But which iron supplement is right for you? The selection is vast, 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 one, and how to optimize your iron absorption.
Here you will learn...
The most important points 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 discomfort such as nausea or constipation.
What iron products are available?
Which form of administration is best for you depends on various factors such as tolerability, the required amount and your personal needs.
You can find an overview of the most common variants here:
tablets
- Most common form of iron supplements
- Mostly contains iron(II) sulfate or iron(III) gluconate
- Often high doses
- May cause gastrointestinal discomfort
Capsules
- Better tolerated than tablets
- Often with added vitamin C or lactoferrin for better absorption.
- Stomach-friendly coating available
Discover our FemBe iron capsules with lactoferrin & vitamin C
Liquid iron supplements
- Ideal for people with swallowing difficulties
- Easy to dose, but often lower concentration
- Longer course of treatment required
Iron infusions
- Fast-acting in cases of severe iron deficiency
- Administered only by doctors
- 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]
The perfect iron supplement
Here are some things to consider 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 absorbed by the body better than iron in its trivalent form, 'iron(III)'. Organic compounds such as iron bisglycinate or ferrous fumarate are particularly bioavailable and, at the same time, gentler on the stomach than inorganic compounds [4].
2. Combination with Vitamin C
Vitamin C helps improve iron absorption. Therefore, a good iron supplement often contains ascorbic acid. Alternatively , vitamin C-rich foods such as orange juice or a piece of bell pepper should be consumed when taking iron [5].
3. Stomach-friendly composition
Stomach-friendly additives 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. In this way, it 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 colorants that may cause allergies or intolerances [7].
5. Flexible Dosage
Preparations with different dosage options are particularly practical, as they can be used both preventively and in cases of acute iron deficiency . This allows you to tailor the dosage to your individual needs.
Discover our FemBe iron capsules with lactoferrin & vitamin C
Conclusion
Iron is essential for the body, but not every supplement delivers the desired effect. To effectively replenish your iron levels, the right supplement should be highly bioavailable, well-tolerated, and free of unnecessary additives. Iron bisglycinate or iron fumarate have proven particularly effective – ideally in combination with vitamin C for optimal absorption.
💡 Tip: Compare different products and find the iron supplement that best suits your body and your needs!
Our expert
Dr. Anne Bansleben
Nutritionist
Key areas:
Product development in analytical chemistry | botany | microbiology
How can I recognize a high-quality iron supplement?
A good iron supplement should:
✔ Contains highly bioavailable iron (e.g., iron bisglycinate or iron fumarate).
✔ Should be 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.
✔ Offers 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 readily absorbed divalent form (Fe²⁺). Therefore, iron should ideally be consumed with vitamin C-rich foods such as orange juice or a vitamin C supplement.
What side effects can iron supplements have?
Common side effects include:
- Gastrointestinal problems (nausea, abdominal pain)
- Constipation or diarrhea
- Dark discoloration of the stool (harmless)
- Metallic taste in the mouth
Tip: Stomach-friendly forms of iron 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:
In case of mild deficiency: 1–3 months
In case of severe deficiency: 3–6 months (or after consulting a doctor)
Preventive use for at-risk groups (pregnant women, vegans): long-term use in low doses
Important: Checking the ferritin level (stored iron) helps to determine the optimal intake duration.
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 should be allowed between consuming it and drinking 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.