Depo-Provera side effects may occur as your body adjusts to the progestin provided by each depo injection. Each Depo Provera shot slowly releases medroxyprogesterone acetate and can protect against pregnancy for a period of 11-14 weeks. Because there can be some more common side effects, it may be helpful to know what to expect when you begin using this method. Unfortunately, there is no way to stop possible Depo Provera side effects or know ahead of time if you will experience them. For some, side effects may continue until the injection wears off (12 to 14 weeks) whereas others may not have any Depo Provera side effects. Being aware of these prior to beginning Depo Provera may help increase your success with this method.
1. Irregular Menstrual Bleeding
Many women stop using Depo Provera during the first year of use due to irregular bleeding (spotting) and/or prolonged bleeding – both of these Depo Provera side effects are especially common for most women during the first 3 months of use. Research has shown that women who have been informed about the potential for either irregular (spotting) bleeding or prolonged bleeding before beginning this method are more likely to continue taking Depo Provera. Most women who have used this method report that the irregular spotting tends to lessen with each shot. According to Pfizer (the manufacturer of Depo Provera), “unusually heavy or continuous bleeding is not a usual effect of Depo Provera and if this happens, you should see your health-care provider right away.
2. No More Periods
After a few shots, Depo Provera usually stops menstruation. It may make your periods very light, and periods may stop altogether. Pfizer reports that over a third of the women in clinical trials had stopped having periods (this is called "amenorrhea") by month 6. After 1 year of use, 55% of the women studied reported no menstrual bleeding and 68% of the women studied reported having no periods after 2 years of use. Many women are willing to go through the initial bleeding in exchange for the chance of not having to have a period anymore.
3. Bone Loss
Depo Provera contains a black box warning about possible bone loss: "Women who use Depo Provera may lose significant bone mineral density (BMD)." BMD measures how much calcium is stored in the bones. This loss of BMD is of particular concern during adolescence and early adulthood. Pfizer warns that Depo Provera use may decrease the amount of calcium in your bones, and the longer you are on Depo Provera, the more calcium you may lose. If you use Depo Provera continuously for more than 2 years, the loss of calcium could increase the risk of your bones weakening, which in turn may increase your risk of osteoporosis and broken bones. Because of this, it is recommended that most women should not use Depo Provera for more than 2 years. A woman should continue with this method (for more than 2 years) only after weighing all other potential options, and it is determined that there are no other birth control methods right for her. Calcium does start to return in the bones once this method is stopped., and your doctor may ask you to take calcium and Vitamin D supplements while using Depo Provera.
4. Weight Gain
Weight gain is frequently cited by women as a reason for discontinuing Depo Provera. That being said, research has shown mixed findings as to whether this method of birth control actually contributes to weight gain. About two-thirds of the women who used Depo Provera in the clinical trials reported a weight gain of about 5 pounds during the first year of use. According to Pfizer, weight gain may continue even after the first year. In a large study of Depo Provera users, women using this method for 2 years gained an average total of 8.1 pounds over those 2 years, or roughly 4 pounds per year. Women who continued for 4 years gained an average total of 13.8 pounds over those 4 years (or about 3.5 pounds per year). Women who continued for 6 years gained an average total of 16.5 pounds over those 6 years (2.75 pounds per year).
5. Return of Fertility
Depo Provera has a prolonged contraceptive effect. Due to this, Pfizer recommends that a woman stop her Depo Provera injections one year before she wishes to become pregnant. This is because it takes an average of 9 to 10 months (sometimes more than a year) to regain fertility and begin ovulating after receiving your last Depo Provera shot. In a large US study of women who discontinued Depo Provera to become pregnant, (based on Life-Table analysis of these data), it is expected that 68% of women who do become pregnant may conceive within 12 months, 83% may conceive within 15 months, and 93% may conceive within 18 months from the last injection. This Depo Provera side effect can occur regardless to the amount of time you have been using this method.
6. Skin Reactions/Pain
Some women report mild pain associated with the injection. In clinical studies, about 6% of women experienced skin reactions in the area where they got their shot. The skin around the injection site may become dimpled or feel lumpy.
7. Less Common Depo Provera Side Effects
In the largest clinical trial of over 3,900 women, the following additional Depo Provera side effects were reported by more than 5% of subjects:
- Abdominal pain or discomfort
- Weakness or fatigue
The following Depo Provera side effects were reported by 1% to 5% of the women:
- Decreased libido
- Leg cramps
- Pelvic pain
- Breast pain
- Hair loss and/or increased hair on the face or body
- Change of appetite
- Skin Rash or spotty darkening of the skin
Depo Provera. Physician Prescribing Information. Pfizer. Accessed: August 24, 2010. http://media.pfizer.com/files/products/uspi_depo_provera_contraceptive.pdf