Iron deficiency: signs, causes and what to do
Iron deficiency is one of the most common nutritional deficiencies. It most often shows up as tiredness, but many other things can also cause tiredness.
In this article you will learn which signs should prompt you to get checked, how to get more iron from food and when supplements are appropriate.
In brief. Iron contributes to the normal formation of red blood cells and haemoglobin, which transports oxygen.1 Only a blood test can confirm iron deficiency.2 Do not take high-dose supplements “just in case”, because too much iron is also harmful.
What is iron needed for?
Iron contributes to:1
- the normal formation of red blood cells and haemoglobin;
- normal oxygen transport in the body;
- the reduction of tiredness and fatigue;
- the normal function of the immune system and normal cognitive function.
What are the signs of iron deficiency?
The most common signs:2
- tiredness and lack of energy;
- shortness of breath when walking or climbing stairs;
- pale skin;
- noticeable heartbeat (palpitations);
- headache;
- brittle nails, hair loss, cracks at the corners of the mouth.
A mild deficiency often causes no signs at all.2 So if you notice several of these signs for more than a few weeks, it is worth having a blood test.
Who is more likely to be deficient?
- Women with heavy periods.2
- Pregnant women – the body needs more iron.2
- Vegetarians and vegans, because plant-based iron is absorbed less well.3
- People who donate blood often.3
- People with certain bowel conditions, e.g. coeliac disease.2
How is iron deficiency diagnosed?
A doctor will order a blood test. Haemoglobin and ferritin are most commonly tested. Ferritin shows how much iron is stored in the body.2 If a deficiency is confirmed, the doctor looks for its cause and chooses the dose and duration of use.
Example. Haemoglobin may still be normal while ferritin is already low. This means that iron stores are running down even though there is no anaemia yet.
How much iron is needed per day?
| For whom | Amount per day | What it means for you |
|---|---|---|
| Men | 11 mg4 | A varied diet is usually enough. |
| Pre-menopausal women | 16 mg4 | It is harder to get from food, especially if periods are heavy. |
| Post-menopausal women | 11 mg4 | The requirement decreases. |
| Safe intake from all sources for adults | Up to 40 mg5 | Take higher doses only if prescribed by a doctor. |
How can you get more iron from food?
Iron of animal origin (in meat, liver, fish) is absorbed better than plant-based iron (in pulses, seeds, dark green vegetables).3
- Combine it with vitamin C. Vitamin C increases iron absorption.1 For example, have a pepper or an orange with a lentil stew.
- Drink tea and coffee between meals. They reduce iron absorption.3
- Take a calcium supplement at a different time from an iron supplement.3
What should you know about iron supplements?
- Look at the amount of iron, not of the compound. For example, 300 mg of an iron compound may contain only 15 mg of iron.
- Add it up. If you take multivitamins with iron and a separate iron supplement, add the amounts from both.
- Common side effects are nausea, constipation and dark stools.2 If this happens, discuss another form or dose with your doctor.
- Taking it every other day. In a study of women with low iron stores, iron taken on alternate days was absorbed better than iron taken daily.6 Discuss such a regimen with your doctor.
Important. Keep iron supplements out of the reach of children. In young children they can cause serious poisoning. If a child has swallowed iron tablets, call 112.3
Selected iron products
Commercial information. These are products available in our shop. This is not a ranking of effectiveness. Before buying, check the ingredients and directions for use on the product page.
Iron, 18mg - 120 vcaps - NOW Foods
Iron bisglycinate, 18 mg of iron per capsule. The manufacturer recommends 1 capsule per day with food. If you also take multivitamins with iron, add up the amounts.7
Iron Protein Plus, 300mg - 100 vcaps - Life Extension
300 mg of iron protein succinylate per capsule, of which 15 mg is iron. A good example of why it is worth looking at the amount of iron rather than of the compound.8
Iron 10 Daily Oral Spray (10mg), Pomegranate - 25 ml - BetterYou
Oral spray, 10 mg of iron in 4 sprays. Pomegranate flavour, labelled as vegan. It contains xylitol, which in larger amounts can have a laxative effect.9
FerraCaps Iron 30 mg 60 capsules - AURA HERBALS
Each capsule contains 30 mg of iron together with 40 mg of vitamin C, vitamins B6 and B12 and 400 µg of folic acid. The dose is higher, so it is advisable to discuss it with a doctor. The capsule contains gelatine.10
Frequently asked questions
Can I take iron without a test?
A small dose in a multivitamin is usually not harmful. However, it is better to take a separate iron supplement only when a test has confirmed a deficiency. In some people, too much iron builds up in the body.2
How long does it take for iron stores to recover?
It usually takes several months. A doctor will usually repeat the blood test to assess whether the supplement is helping.2
Is spinach high in iron?
Spinach does contain iron, but plant-based iron is absorbed less well than the iron found in meat.3 Eat it together with foods containing vitamin C.
Scientific sources
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods (consolidated version). EUR-Lex
- NHS. Iron deficiency anaemia. nhs.uk
- NIH Office of Dietary Supplements. Iron – Fact Sheet for Health Professionals. ods.od.nih.gov
- EFSA NDA Panel. Scientific opinion on dietary reference values for iron. EFSA Journal. 2015;13(10):4254. doi:10.2903/j.efsa.2015.4254
- EFSA NDA Panel. Scientific opinion on the tolerable upper intake level for iron. EFSA Journal. 2024;22(6):8819. doi:10.2903/j.efsa.2024.8819
- Stoffel NU, Cercamondi CI, Brittenham G et al. 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: two open-label, randomised controlled trials. Lancet Haematol. 2017;4(11):e524–e533. doi:10.1016/S2352-3026(17)30182-5
- NOW Foods. Iron, 18 mg, 120 capsules. Product label.
- Life Extension. Iron Protein Plus, 300 mg, 100 capsules. Product label.
- BetterYou. Iron 10 Daily Oral Spray, Pomegranate, 25 ml. Product label.
- AURA HERBALS. FerraCaps iron 30 mg, 60 capsules. Product label.
Disclaimer. This article is for information purposes only and does not replace a consultation with a doctor or pharmacist. Food supplements are not intended to treat or prevent diseases and are not a substitute for a varied diet and a healthy lifestyle. Before taking supplements, especially during pregnancy or breastfeeding, if you have a chronic condition or if you are taking medicines, consult a healthcare professional.
