Strong evidence · Vitamins & minerals
Iron
Oxygen transport — but only with a proven deficiency
Strong evidence
Multiple good studies and reviews point the same way.
Iron deficiency can cause fatigue and disappointing performance. Whether you have a deficiency can only be seen from your blood values (including ferritin). Supplementing only makes sense with a proven deficiency.
- Dosage
- Only based on a blood value
- Timing
- Discuss with your doctor; taking it every other day as a single dose seems to be absorbed better
- Approx. price
- €5–12 per month
Watch out
Don't take iron just to be safe: your body has difficulty getting rid of an excess. Have ferritin and haemoglobin tested first. In a small study of 40 women with low iron stores, iron taken every other day as a single morning dose was absorbed 34% better than daily (Stoffel, 2017).
Frequently asked questions about supplements
How much Iron per day?
Only based on a blood value
When should you take Iron?
Discuss with your doctor; taking it every other day as a single dose seems to be absorbed better
Does Iron really work?
Strong evidence. Multiple good studies and reviews point the same way.
What does Iron cost?
€5–12 per month
Basics first, then the tub
Supplements are called supplements because they add to something. Sleep, a protein intake that hits your protein calculator , a programme where you lift progressively heavier and enough food together do a hundred times more than the best-researched item on this list. Once those are in place, creatine, caffeine and vitamin D in winter are the three you can spend money on with a clear conscience — for less than ten euros a month combined.
Sources
- Stoffel NU et al. (2017). Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women. Lancet Haematol 4(11):e524-e533. (randomized trial, n = 40)
More supplements in this category
Last updated: October 2026
This page summarises scientific research and is not medical advice. If you take medication, are pregnant or have a liver, kidney or thyroid condition, discuss supplements with your doctor or pharmacist — even the innocent-looking ones.
← All supplements