Iron deficiency

Iron lets the blood carry oxygen. Iron deficiency is the most common nutrient deficiency in the world, and it is most common in women who have periods. Not every anaemia is caused by low iron, and low iron can exist without anaemia.

Symptoms

Most signs are non-specific: low iron causes them, and so do many other things.

• tiredness, even after enough sleep;
• breathlessness or a pounding heart on mild effort, light-headedness on standing;
• brittle, ridged or spoon-shaped nails;
• a sore or smooth tongue, cracks at the corners of the mouth;
• restless legs in the evening or at night;
• craving ice or non-food things such as chalk, starch or soil. This is one of the few genuinely characteristic symptoms, although only a minority of people with low iron have it.

Low iron can also cause no symptoms at all, especially before anaemia develops.

Who is at risk

Circumstances say more than symptoms:

• heavy periods;
• pregnancy and the year after birth;
• frequent blood donation;
• little or no meat;
• years of stomach-acid reducers such as omeprazole;
• stomach or bowel surgery, coeliac disease, inflammatory bowel disease;
• a lot of endurance training.

Which test to ask for

Ask about ferritin with a full blood count. If the result is doubtful or you are unwell, transferrin saturation or C-reactive protein are added.

Two pitfalls:

• ferritin rises with inflammation and can look normal when iron is low;
• a normal haemoglobin does not rule out low iron: stores run down before anaemia appears.

Men and women after the menopause

In these groups low iron usually means blood is being lost somewhere. In about a third of them, iron-deficiency anaemia has a cause in the gut. See a doctor to find the cause, rather than buying iron.

What not to do

Do not take iron “just in case”. Too much iron damages the liver, heart and other organs, and builds up silently in people with hereditary haemochromatosis. Iron also reduces how well levothyroxine is absorbed. Test first, then decide with a doctor.