LIBC refers to the additional, reserve amount of iron that can still bind to transferrin. (see transferrin).

There is approximately 2.5 mg of iron in the blood, which is mainly bound to a protein, transferrin, which is necessary for the transport of the trace element as well as to protect the body from the accumulation of toxic iron ions.

Typically, transferrin iron saturation is approximately 30 to 40% of the maximum possible saturation level.

Total iron-binding capacity of serum results from adding up the LIBC and serum iron. This formula can be used to calculate the iron saturation factor, which normally is from 16% to 25%:

serum iron/TIBC*100%

The analysis is necessary to determine the cause of anemia.