bioavailability

Amount of a substance that becomes available (reaches the target organ or systemic circulation) to an organism's body for bioactivity when introduced through ingestion, inhalation, injection, or skin contact. Rate of bioavailability depends on factors such as the type of the substance (whether fat soluble or water soluble, for instance) and the composition of diet. The ability of a body to absorb lead, for example, is enhanced if the diet is deficient in calcium or iron.