Depo-Provera (medroxyprogesterone) is a drug used for birth control that must be injected under the skin or into a muscle every three months. It is a type of progestin and works by preventing ovulation and by thinning the lining of the uterus. It is also used to treat endometriosis - a disorder characterized by the spread of tissue from the uterus to other parts of the body.
I discussed your question with Victoria Maizes, M.D., executive director of the Arizona Center for Integrative Medicine. While she rates Depo-Provera as a very effective method of birth control, she worries about its effect on bones. The drug is associated with a loss of bone density resulting in an increased risk of osteoporosis. Worse, the bone loss associated with the injections does not appear to be reversed when women stop using the drug. For this reason, Depo-Provera isn't recommended for long-term use (two years maximum for most women) and shouldn't be used by young women whose bones are still growing. Women who do use Depo-Provera for birth control are urged to eat plenty of foods that are high in calcium and to make sure that they get adequate vitamin D.
Apart from that, women who take Depo-Provera may experience many side effects. The most serious of these is a slightly increased risk of breast cancer and of pulmonary embolism and stroke due to increased clotting tendency of blood.
You don't mention your daughter's age. If she's a teenager, I would be surprised if her physician would agree to treat her with Depo-Provera for birth control in view of the threat to growing bones. I would encourage your daughter to have a frank talk with her physician about the benefits and risks of the various methods of birth control and to consider safer options.
Andrew Weil, M.D.