Iron deficiency symptoms tend to arrive quietly: a tiredness that sleep does not fix, less puff on the stairs, friends saying you look pale. The body uses up its iron stores first, and anaemia only follows once they are empty. It is very common in women with heavy periods and during pregnancy, but in a man or a woman past the menopause it always needs a cause to be found.
In short
| What to know | The benchmark |
|---|---|
| Most common signs | Tiredness, shortness of breath, palpitations, paler skin than usual |
| Less common signs | Hair loss, a sore tongue, spoon-shaped nails, cravings for ice, restless legs |
| First value to fall | Ferritin, which reflects iron stores: below 15 micrograms per litre confirms deficiency in a healthy adult (WHO, 2020) |
| Anaemia | Haemoglobin below 120 g/L in non-pregnant women and 130 g/L in men (WHO) |
| Daily need | 8.7 mg for men and women aged 50 and over, 14.8 mg for women aged 19 to 49 (NHS) |
| Most common causes | Heavy periods, pregnancy, bleeding from the stomach or bowel, a diet low in iron |
What iron does
Iron is part of haemoglobin, the protein in red blood cells that carries oxygen from the lungs to the rest of the body. Muscles and many of the reactions that produce energy in your cells also depend on it.
The body keeps a reserve, stored as ferritin. When intake does not cover losses, that reserve is used first. Doctors therefore distinguish two stages: iron deficiency without anaemia, when stores are low but haemoglobin is still normal, and iron deficiency anaemia, when there is no longer enough iron to make red blood cells. The NHS describes it as the most common type of anaemia.
The symptoms of iron deficiency
The most common signs
According to the NHS, the usual symptoms are:
- tiredness and lack of energy;
- shortness of breath, especially on effort;
- noticeable heartbeats (palpitations);
- paler skin than usual.
Headaches and difficulty concentrating are also common complaints. Some people feel tired with low ferritin even before their haemoglobin drops; others notice nothing until the anaemia is marked, because the body adapts when the fall is slow.
Less common signs
The NHS also lists signs that are less frequent:
- hair loss, with more hair coming out when brushing or washing it;
- a sore tongue, painful sores in the corners of the mouth;
- spoon-shaped nails;
- wanting to eat non-food items such as ice or paper (pica);
- restless legs, itching, ringing in the ears, food tasting strange;
- difficulty swallowing.
Why symptoms alone are not enough
None of these signs is specific. Tiredness has many other causes, from poor sleep and stress to thyroid problems or vitamin D deficiency. A sore tongue and pins and needles can also point to vitamin B12 deficiency. Only a blood test can tell whether iron is involved.
The most common causes
Heavy periods
This is the most frequent cause in women of childbearing age. The NHS considers periods heavy if you need to change a pad or tampon every 1 to 2 hours, or empty a menstrual cup more often than recommended. Heavy periods can be treated, which also helps prevent the deficiency from coming back.
Pregnancy
Needs rise sharply to build the baby’s blood and the placenta. In pregnancy, the NHS notes that iron deficiency is most often due to a lack of iron in the diet, and iron levels are checked as part of antenatal care.
Bleeding from the stomach or bowel
Slow bleeding in the digestive tract can go unnoticed for months. Causes include stomach ulcers, inflammation of the gut, and long-term use of anti-inflammatory painkillers such as ibuprofen or aspirin. Less often, it is a cancer of the stomach or bowel. This is why unexplained iron deficiency in a man or a woman who no longer has periods is always investigated.
Diet and absorption
Iron from meat, fish and shellfish is absorbed more easily than iron from pulses, cereals and vegetables. Vegetarians and vegans can meet their needs but have less margin. Coeliac disease and stomach surgery can also reduce absorption. Regular blood donors are at higher risk too.
The blood test and what it shows
Your GP will usually ask for a full blood count, which measures haemoglobin and the size of the red blood cells, and a ferritin test.
| Test | What it shows | Benchmark |
|---|---|---|
| Ferritin | Iron stores | Below 15 micrograms per litre confirms deficiency in a healthy adult (WHO, 2020) |
| Haemoglobin | Whether there is anaemia | Below 120 g/L in non-pregnant women, below 130 g/L in men (WHO) |
| MCV (mean cell volume) | The size of red blood cells | Often low in iron deficiency, but it can be normal |
| Transferrin saturation | The iron available in the blood | Useful when ferritin is unclear |
Ferritin rises with any inflammation or infection, so a “normal” ferritin does not always rule out a deficiency. In people with inflammation, the WHO considers that a value below 70 micrograms per litre may already indicate a lack of iron. Your GP reads the result alongside the rest of the blood count, and the reference range printed by your laboratory is the one that applies.
If the cause is not clear, the NHS explains that the GP may suggest a FIT test, which looks for hidden blood in a stool sample, or refer you for further checks.
How much iron you need and where to find it
The NHS gives these daily amounts:
- 8.7 mg a day for men aged 19 and over;
- 14.8 mg a day for women aged 19 to 49;
- 8.7 mg a day for women aged 50 and over.
Good sources include red meat, liver (avoid it if you are pregnant), beans and lentils, dark-green leafy vegetables such as watercress and curly kale, dried fruit such as apricots, and breakfast cereals fortified with iron.
To get more out of plant iron:
- pair it with a source of vitamin C, such as peppers, tomatoes, citrus fruit or a glass of orange juice;
- keep tea and coffee away from main meals, because they reduce iron absorption.
How it is treated
Treatment is decided by your GP and always goes with finding the cause:
- when a blood test confirms iron deficiency anaemia, iron tablets are usually prescribed, often for around six months to refill the stores as well as correct the haemoglobin;
- side effects such as constipation, diarrhoea, stomach pain, nausea or darker stools are common; the NHS suggests taking the tablets with or soon after food and keeping going, but tell your GP if they are hard to tolerate;
- repeat blood tests over the following months check that your levels are coming back to normal.
Do not start iron supplements on your own to treat tiredness. They can correct the anaemia while the cause, such as bleeding in the bowel, goes undiagnosed. For people not under medical supervision, the NHS says that taking 17 mg or less a day of iron supplements is unlikely to cause any harm; higher doses are for when a GP advises them.
More on common deficiencies in our Health section.
When to see a GP
Book an appointment if you have:
- tiredness, shortness of breath or pale skin that last several weeks;
- hair loss, brittle or spoon-shaped nails, or cravings for ice without explanation;
- periods that are heavy or last longer than usual;
- a pregnancy, or plans for one, with a diet low in iron.
Ask for an urgent appointment if you have black or bloody stools, unexplained weight loss, a lasting change in your bowel habits or tummy pain that does not go away, or if iron deficiency is found and you are a man or a woman past the menopause.
Call 999 if you have chest pain, severe shortness of breath at rest, you faint, or you vomit blood.
