Quick answer
What are iron blood tests?
Iron blood tests measure ferritin, which reflects your iron stores, alongside serum iron and transferrin saturation, to diagnose iron deficiency anaemia. Ferritin is usually low in deficiency but can appear normal if inflammation is present. Your GP treats the underlying cause and may prescribe iron supplements.
What iron blood tests measure
Iron blood tests typically include ferritin, serum iron, total iron-binding capacity and transferrin saturation. These results are interpreted together with a full blood count, since each measurement gives a different piece of the overall picture of your iron status.
Causes of iron deficiency
Iron deficiency can be caused by menstrual blood loss, an inadequate diet, poor absorption of iron in the gut, or bleeding from the gastrointestinal tract. Pregnancy also increases the body’s demand for iron, which can lead to deficiency if intake does not keep pace.
How iron deficiency is treated
Treatment usually involves oral ferrous sulphate or an alternative iron preparation if this is not tolerated. Alongside this, the underlying cause needs to be addressed, which may include an endoscopy if gastrointestinal bleeding is suspected.
Monitoring iron levels during treatment
Ferritin and haemoglobin are usually repeated after a period of weeks to check that levels are improving. Treatment continues until iron stores are replenished and the underlying cause has been properly addressed.
Common questions about the iron blood tests
- What does a low ferritin level mean?
- A low ferritin level means your iron stores are becoming depleted, even before full anaemia develops. Iron supplementation is often needed at this stage to prevent things worsening.
- Can ferritin be normal even with iron deficiency?
- Yes, inflammation in the body can raise ferritin and mask an underlying iron deficiency. Your GP interprets ferritin alongside markers such as CRP and your overall clinical picture.
- What are the side effects of iron tablets?
- Constipation and black stools are common side effects of iron tablets. Alternative formulations are available if the usual tablets do not suit you.
- When does iron deficiency need further investigation?
- Iron deficiency in men and in women past the menopause usually needs investigation of the gut for a possible source of bleeding. This is because these groups are less likely to have an obvious cause such as heavy periods.