Haemoglobin is the red pigment within red blood cells. Its role is to transport oxygen around the body. Haemoglobin is manufactured in the body from iron. Normal levels are at least 13g per 100ml of blood for men, and at least 11.5g for women. Low haemoglobin is termed anaemia. Excessive haemoglobin is called polycythaemia. It is more common for haemoglobin levels to be too low than too high, especially in women.
Lowered haemoglobin means insufficient oxygen is supplied to the tissues. This results in tiredness and lethargy. Anaemic patients may be breathless, pale and have a rapid pulse. The pulse increases because the heart tries to compensate for inadequate oxygen by pumping faster. Over time, this can cause heart problems, chest pains and dizzy spells. In children, anaemia can cause heart murmur, developmental delay and lowered resistance to infection. Both anaemia and polycythaemia may cause headaches; both place a strain on the heart. Polycythaemia increases the viscosity (thickness) of blood, sometimes leading to stroke.
Raised haemoglobin may indicate dehydration, heavy smoking or underlying disease. Anaemia is most commonly caused by bleeding, including heavy menstruation. Commonly, women become anaemic in pregnancy due to the baby's demand for iron. Deficiencies of vitamin B12 or folic acid also inhibit red blood cell production. Crohn's and coeliac's patients cannot properly digest iron. Although most Western diets contain sufficient iron, vegetarian and vegan diets may not. Iron from vegetable sources is less readily digested than iron in meat. Women cutting calories risk consuming insufficient iron. Athletes have increased requirements for haemoglobin and increased iron loss through sweat.
Anaemia is associated with kidney failure, cirrhosis and diabetes. It may indicate bleeding from the stomach or bowel, associated with ulcers or colon cancer. Insufficient red blood cell production may indicate leukaemia. Excessive haemoglobin may indicate severe lung disease or excessive production in the bone marrow. Neither anaemia nor polycythaemia are diagnoses in themselves – it is essential to investigate the cause. Never self-medicate with iron supplements – too much iron can be harmful, even fatal.
Doctors will check for elevated heart and breathing rates indicative of anaemia. A full blood count (FBC) includes a haemoglobin level (Hb) test and a haematocrit test. The haematocrit reveals the percentage of the blood comprised by red blood cells. Haemoglobin may be low because there are insufficient red cells, or because they are too small or contain insufficient haemoglobin. Where an FBC reveals abnormal haemoglobin levels, doctors may suggest a faecal occult blood test to detect bleeding from the stomach or bowel, a bone marrow biopsy, or in cases of excess red blood cells, a red cell mass study.
Doctors must investigate and treat the cause. Severe polycythaemia is treated by blood-letting; serious anaemia with a blood transfusion. Lesser deficiencies may be prescribed an iron supplement. Beyond this, patients can maintain normal haemoglobin levels by eating a balanced diet. Foods to prevent anaemia include meat, eggs, milk, green leafy vegetables, fortified cereals and oranges. Cutting down on tea and coffee and cooking using iron cookware also helps.