Transferrin saturation

Some laboratories use 16 to 50 or 20 to 55 %; it follows the serum iron, so it is highest in the morning and after iron tablets; use the range your lab printed.

Transferrin saturation is the proportion of the iron carrying protein that is actually carrying iron, calculated from the serum iron and the transferrin or TIBC. It shows how much iron is available to the tissues right now. It is low when iron is short and high when there is more iron than the body can store.

Doctors request it as part of iron studies when looking into anaemia, and it is the key test when iron overload is suspected, since a persistently high saturation is the earliest change in haemochromatosis. It is also used in kidney disease and heart failure to decide whether iron is short.

• A recent meal or iron tablet, for a few hours
• Iron overload, including haemochromatosis and repeated transfusions
• Liver disease
• Conditions where red cells are broken down early
• Low vitamin B12 or folate
• Some bone marrow conditions

• Low iron stores
• Inflammation or infection
• Later in the day, following the daily rhythm of serum iron
• Long-term kidney disease
• Pregnancy

• It follows the serum iron, so the time of day and any recent meal or iron tablet change it a great deal
• A single high value is common and is repeated fasting in the morning before any conclusion is drawn
• A recent infection lowers it

Best taken in the morning, fasting, with no iron tablets for 24 hours beforehand. A single high value is repeated before further tests.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.