Ferritin blood test: normal range explained

A ferritin test measures the level of ferritin, a protein that binds iron and stores it, mostly in the liver, spleen and bone marrow. Testing.com says the result reflects iron in reserve rather than iron moving through the blood, and that it can show low iron stores before symptoms develop.

Ferritin is not only an iron marker. MedlinePlus and Testing.com both say it rises with inflammation, infection and liver disease, even when iron stores are normal, so a result in range does not always rule out low iron.

Doctors order ferritin, often with other iron tests, to check whether the body is storing the right amount of iron. MedlinePlus says it can help diagnose or rule out iron deficiency anaemia and iron overload (haemochromatosis), and can be used in liver disease, restless legs syndrome and adult Still disease.

It is also used to screen people at higher risk of low iron before symptoms appear, such as those with heavy menstrual bleeding or pregnancy, and to follow treatment. NHS says a GP usually starts with a full blood count when iron deficiency anaemia is suspected.

Ferritin can rise or fall for reasons other than the amount of iron in store.

• Inflammation from infection or surgery, autoimmune disorders, liver disease, cancer, obesity and alcohol use disorder can raise ferritin.
• An overactive thyroid and frequent red cell transfusions are listed causes of a high level.
• Heavy menstrual bleeding, pregnancy, a low-iron diet and bleeding in the stomach or bowel lower it over time.
• Poor absorption of iron from food, medicines or vitamins can lower it, and MedlinePlus says some medicines raise or lower ferritin.
• Biotin supplements can interfere with some assays; Testing.com says to stop them at least 72 hours before the draw, if your doctor agrees.
• NHS says large amounts of tea, coffee, milk and dairy, and wholegrain cereals high in phytic acid, make iron harder to absorb.