What is iron deficiency?
Iron deficiency occurs when the body does not have enough iron to meet its needs. Iron is an essential mineral, needed above all to make haemoglobin — the substance in red blood cells that binds oxygen and carries it around the body. When iron runs low, the body cannot make enough healthy haemoglobin, and eventually not enough healthy red blood cells, which is called iron deficiency anaemia. This is one of the most common nutritional deficiencies worldwide.
Iron deficiency can develop gradually, and mild deficiency may cause few or no symptoms at first. As it progresses toward anaemia, symptoms like tiredness and weakness become more noticeable, because the body's tissues are not getting as much oxygen as they need. The good news is that iron deficiency is common, well understood, and usually straightforward to treat once the cause is identified — though finding and addressing the underlying cause is an important part of managing it properly.
Symptoms
The symptoms of iron deficiency, especially once it causes anaemia, largely stem from tissues not getting enough oxygen. They develop gradually and can include:
- •Tiredness and lack of energy, often the most noticeable symptom
- •Shortness of breath, especially on exertion
- •Pale skin
- •Heart palpitations (noticeable heartbeats)
- •Headaches and dizziness
- •Brittle nails and hair changes
- •Unusual cravings for non-food items like ice (in some cases)
Causes
Iron deficiency develops when the body loses iron, uses more than it takes in, or does not absorb or consume enough. Identifying the cause is an important part of treatment. Common causes include:
- •Blood loss — a very common cause, including heavy periods in women
- •Blood loss from the digestive system, which may need investigation
- •A diet low in iron
- •Pregnancy, which increases iron needs
- •Conditions that reduce iron absorption from the gut
- •Increased needs during growth in children and teenagers
Diagnosis, treatment and diet
Iron deficiency is diagnosed with blood tests that check for anaemia and measure iron stores (such as ferritin). Because finding low iron is only part of the picture, a doctor will also consider why it has happened, and may recommend further investigation to find the source, particularly where blood loss from the digestive system is possible. Identifying and treating the underlying cause is as important as replacing the iron.
Treatment usually involves iron supplements to restore the body's iron levels, taken as directed for a period of time, along with treating the cause. Iron tablets can sometimes cause side effects like constipation or tummy upset, so a doctor or pharmacist can advise on how to take them and what to do if they cause problems. Alongside supplements, eating more iron-rich foods supports recovery and helps maintain levels: good sources include red meat, pulses, beans, dark green leafy vegetables, and fortified foods. Vitamin C (for example from fruit) can help the body absorb iron from plant sources.
Recovery, prevention and when to see a doctor
With treatment, most people with iron deficiency recover well, and their energy and other symptoms improve as iron levels and haemoglobin return to normal. It usually takes some weeks to months to fully replenish the body's iron stores, so treatment is often continued for a while after symptoms improve, and follow-up blood tests check that levels have recovered. Keeping up with any treatment and addressing the cause reduces the chance of it returning.
For prevention and maintenance, a balanced diet containing iron-rich foods supports healthy iron levels, which is particularly relevant for groups with higher needs or losses — such as women with heavy periods, pregnant women, growing children, and those following diets low in iron. Where periods are heavy, addressing that can help; where diet is the issue, adjusting it or supplementing under guidance helps.
It is important to see a doctor rather than simply self-treating suspected iron deficiency, both to confirm it with a blood test and, crucially, to identify the cause. This matters because some causes — particularly unexplained blood loss from the digestive system — need investigation in their own right. For most people, though, iron deficiency is a common, treatable condition, and once the cause is addressed and iron replaced, they recover fully.