An exogenous or from outside the body method of replacing or supplementing what the body is lacking or deficient in. Replacement therapy can have many different forms. Some deficiencies can be treated using oral medications, such as pills or liquids, others may need to be given subcutaneously, intramuscularly, or intravenously. Replacement therapy is carried out until the body has or can produce what it needs on a regular basis in enough quantities to keep it healthy.