What iron is and when we speak of a deficiency
Iron is a mineral the body needs to make haemoglobin – the protein in red blood cells that carries oxygen around the body. Part of the iron is kept in stores, which are estimated in the blood through the protein ferritin. The body cannot make iron itself, so it comes from food.
A deficiency develops gradually: first the stores run down (low ferritin), and only later does haemoglobin start to fall. That is iron deficiency anaemia, which according to the World Health Organization (WHO) is the most common form of anaemia. The WHO estimates that around 30 percent of women aged 15 to 49 and 37 percent of pregnant women have anaemia.
Symptoms of iron deficiency and who is more at risk
The most common symptoms of iron deficiency and anaemia are tiredness, pale skin, shortness of breath on exertion, a pounding heart and headaches. Less often there is hair loss, brittle or spoon-shaped nails, a sore tongue, cracks at the corners of the mouth, restless legs and unusual cravings for ice or non-food items (pica). The signs are not specific to iron: a lack of vitamin B12, thyroid disease, too little sleep or stress can look similar.
Women with heavy periods, pregnant women, frequent blood donors, vegans and vegetarians, and people with coeliac disease, inflammatory bowel disease or after digestive surgery are affected more often. In men and in women after the menopause, iron deficiency is often a sign of hidden blood loss, for example from the gut – so a doctor also looks for the cause, not only at replacing iron.
Why not to take iron on your own
The only reliable way to find out whether you are really low in iron is a blood test: a GP usually orders haemoglobin, ferritin and sometimes other markers. Only the result shows whether there is a deficiency, how marked it is and whether the cause needs to be found.
The body does not actively get rid of excess iron, so long-term use without a need can lead to iron building up in organs, which is a particular risk with hereditary haemochromatosis. High doses can cause constipation, nausea and stomach pain, and for young children swallowing iron tablets can be fatal, so keep them out of their reach. Leave the dose and duration to a doctor.
Iron-rich foods
Iron in food comes in two forms. Haem iron from meat, fish and liver is absorbed relatively well, non-haem iron from pulses, seeds, grains and vegetables less so. The table below lists the iron content per 100 grams of some foods according to the USDA FoodData Central database.
| Food | Iron (mg/100 g) | Origin |
|---|---|---|
| Sesame seeds | 14.6 | plant |
| Chicken liver, cooked | 11.6 | animal |
| Pumpkin seeds | 8.8 | plant |
| Mussels, cooked | 6.7 | animal |
| Cashew nuts | 6.7 | plant |
| Rolled oats | 4.3 | plant |
| White beans, cooked | 3.7 | plant |
| Lentils, cooked | 3.3 | plant |
| Chickpeas, cooked | 2.9 | plant |
| Spinach, raw | 2.7 | plant |
| Tofu, firm | 2.7 | plant |
| Egg | 1.8 | animal |
A tip for your plate: vitamin C in the same meal lets the body absorb more iron from plant foods. So pair lentils or chickpeas with peppers, oats with kiwi or strawberries, and a spinach salad with orange or lemon juice. Drink tea, coffee and milk between meals rather than with them, as they make iron harder to absorb.
Frequently asked questions
What are the first signs of iron deficiency?
Most often tiredness and lack of energy, pale skin, shortness of breath on exertion and headaches. At first the signs can be barely noticeable or absent, so a deficiency is often found only by a blood test.
How do I check whether I am low in iron?
With a blood test at your GP. It usually looks at haemoglobin, which shows anaemia, and ferritin, which shows the iron stores. The self-check on this page is only an orientation and does not replace a test result.
What is the difference between iron deficiency and anaemia?
With iron deficiency the stores (ferritin) are low, while haemoglobin may still be in the normal range. When the deficiency lasts longer, haemoglobin starts to fall too – that is iron deficiency anaemia. Anaemia can also have other causes, for example a lack of vitamin B12 or folate.
Which foods are richest in iron?
Among the foods in the table above, sesame and pumpkin seeds, liver, mussels, cashews and oats have the most iron, and among everyday dishes pulses such as lentils, beans and chickpeas. The body absorbs iron from plant foods better if you also eat a food with vitamin C in the same meal.
When should I see a doctor straight away?
Call 112 or go to an emergency department straight away if you have chest pain, severe shortness of breath, fainting, black tarry stool or blood in your stool or vomit. Book a GP appointment if signs of iron deficiency last for weeks, if you are pregnant or if you have very heavy periods.
Sources
- NHS – Iron deficiency anaemia
- NHS – Iron (vitamins and minerals)
- Mayo Clinic – Iron deficiency anemia: Symptoms and causes
- WHO – Anaemia (fact sheet)
- NIH Office of Dietary Supplements – Iron: Fact Sheet for Consumers
- USDA FoodData Central – food composition
Updated: October 2026
An informational test, not a substitute for medical advice.