Progesterone is primarily used to promote fertility in women with low blood Progesterone levels. Low Progesterone levels make the tissue lining the uterus thinner and less nutrient-rich than is required for implantation by the fertilized egg and growth of the embryo. Progesterone treatment after ovulation can make the uterine lining thicker and more suitable for implantation to occur. Progesterone is also needed during pregnancy for normal fetal development and to relax the uterus. Progesterone supplements may therefore be prescribed for several weeks during early pregnancy, up until the placenta is well formed and is able to produce sufficient Progesterone to meet the needs of the growing fetus.

Besides pregnancy-related uses, Progesterone is also prescribed to control bleeding in women who are not ovulating. In women who wish to postpone becoming pregnant, high-dose Progesterone injections act by preventing ovulation and by making mucus in the lower reproductive tract thicker. This thickened mucus makes it more difficult for sperm to ascend up through the cervix and uterus into the fallopian tube.

In post-menopausal women with a uterus who are also receiving estrogen replacement, Progesterone is given to control overgrowth of the uterine lining. Short-term hormone replacement therapy during menopause may also reduce side effects such as hot flashes.

Progesterone can be taken in the form of capsules, injections or vaginal suppositories. While a number of Progesterone creams and natural Progesterone products are available, some without prescription, these may be ineffective in treating hot flashes, preventing osteoporosis, increasing sexual desire or preventing endometrial and breast cancer. Both the American Menopause Society and the American College of Obstetricians and Gynecologists caution against the use of such compounds with unproven benefits and unknown risks. It is always advisable to take Progesterone under the careful monitoring of a trained and licensed medical provider.