Total iron binding capacity

Some laboratories use 45 to 70 or 47 to 81 umol/L; it rises in pregnancy and on oestrogen-containing medicines; use the range your lab printed.

The total iron binding capacity is the amount of iron the blood could carry if every carrier protein (transferrin) were fully loaded. It is another way of expressing the amount of transferrin. When iron stores are low, the body makes more transferrin and the TIBC rises; the serum iron divided by the TIBC gives the transferrin saturation.

Doctors request it as part of iron studies, to calculate the transferrin saturation and to help separate low iron stores from the low iron of inflammation. Many laboratories print either TIBC or transferrin rather than both.

• Low iron stores
• Pregnancy
• Oestrogen-containing medicines

• Inflammation or infection from any cause
• Liver disease
• Poor nutrition or protein loss
• Iron overload
• Long-term kidney disease
• Some cancers

• It rises in pregnancy and on oestrogen-containing medicines as an expected effect
• Any recent infection or inflammation lowers it
• Some laboratories calculate it from transferrin rather than measuring it, so small differences between laboratories are common

No fasting needed for TIBC itself; the paired serum iron is best taken fasting in the morning.

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