The Depo shot (Depo-Provera) is a hormonal birth control injection given every three months, and it comes with a well-documented list of side effects. The most common are irregular bleeding or spotting (affecting 57% of users in the first year), weight gain over 10 pounds (38% of users by two years), and headaches (17%). Most side effects ease over time, but some, like bone density loss, have prompted an FDA boxed warning that limits recommended use to two years.
Irregular Bleeding and Period Changes
Changes to your menstrual cycle are the single most reported side effect and the top reason people stop using the shot. In the first year, 57% of users experience irregular bleeding or spotting. This can mean anything from light spotting between periods to longer, unpredictable bleeding episodes. The pattern usually shifts over time: by month 12, about 55% of users stop getting a period entirely. By 24 months, irregular bleeding drops to 32% as more users reach full amenorrhea.
For some people, losing their period is a welcome benefit. For others, the months of unpredictable spotting leading up to that point are frustrating enough to quit. In clinical trials, 8.2% of participants discontinued because of bleeding issues, making it the most common reason for stopping.
Weight Gain
Weight gain is real with the Depo shot, though it tends to be gradual. By 24 months, 38% of users gain more than 10 pounds. Over three years, users gain an average of about 11 pounds, and research shows most of that increase is body fat rather than water retention. The gain is also concentrated around the midsection, with a measurable shift in the ratio of central to peripheral fat.
This stands in contrast to other hormonal methods. In a comparative study, users of birth control pills and hormonal implants actually lost a small amount of weight over one year, while Depo users stayed roughly the same in year one and then gained steadily in years two and three. Weight gain was significant enough that 2% of clinical trial participants stopped the shot specifically because of it.
Headaches, Mood, and Energy
Headaches affect about 17% of users, and nervousness is reported by 11%. Other neurological side effects include dizziness (6%), insomnia (1%), and fatigue (4.2%). Decreased sex drive affects roughly 6% of users.
Depression and mood changes are a more complicated picture. The FDA label lists depression at a rate of 1.5%, but real-world experiences vary widely. A three-year study of 183 women found that Depo users had higher depressive symptoms compared to non-users, and women who eventually stopped the shot had elevated depression levels right around the time they quit. However, a separate large study of 495 women found that those who continued using the shot actually saw a slight improvement in depression scores over 12 months. The American College of Obstetricians and Gynecologists has stated that the shot does not appear to be broadly associated with mood worsening, but individual responses clearly differ. If you have a history of depression, this is worth monitoring closely.
Bone Density Loss
This is the side effect serious enough to earn the FDA’s strongest label warning. The Depo shot lowers estrogen levels, which leads to measurable bone mineral density loss. The longer you use it, the more bone you lose, and the FDA recommends against using it for more than two years unless other birth control options aren’t suitable for you.
The good news is that bone density does partially recover after stopping. In adults, the spine tends to return to baseline levels within a couple of years. But recovery isn’t always complete. Women who used the shot for more than two years did not fully regain bone density at the hip, even five years after their last injection. This is especially concerning for teenagers and young adults, whose bodies are still building peak bone mass. In a study of adolescent users, hip bone density had not fully recovered by five years post-treatment.
Getting adequate calcium and vitamin D supports bone health during and after use. The standard recommendation for most women under 50 is 1,000 mg of calcium daily, and weight-bearing exercise (walking, running, strength training) also helps maintain bone density.
Digestive and Physical Symptoms
A cluster of physical side effects falls in the 1% to 5% range. Abdominal pain or discomfort affects about 11% of users, making it one of the more common complaints. Nausea (3.3%), bloating (2.3%), and leg cramps (3.7%) round out the physical symptoms you might notice in the first few months. Fluid retention or mild swelling affects about 2.2% of users, and back pain shows up in roughly 2.2%.
Skin and Hair Changes
Some users notice skin breakouts: acne is reported in about 1.2% of users. Hair thinning or reduced hair growth occurs at a similar rate (1.1%), and about 1.1% develop a rash. These are less commonly discussed side effects, but they can be distressing when they appear, particularly since the shot lasts three months and can’t simply be stopped like a daily pill.
Breast Tenderness and Reproductive Symptoms
Breast pain affects about 2.8% of users. Vaginal discharge (2.9%) and vaginal irritation (1.2%) are also reported. Hot flashes occur in about 1% of users, which makes sense given that the shot suppresses estrogen in a way that partially mimics menopause.
On the cancer front, the data is reassuring. Research from ACOG shows that injectable contraceptives like Depo-Provera do not appear to increase breast cancer risk, and hormonal contraception in general is associated with decreased risk of ovarian, endometrial, and colon cancers.
Delayed Return to Fertility
Unlike the pill or an IUD, the Depo shot takes considerably longer to clear your system. After your last injection, it can take 10 months or more before you start ovulating again. About 50% of people who stop using it conceive within 10 months. One study found the average time to return of fertility was roughly five to seven months depending on dose, but some women wait a year or longer. If you’re planning a pregnancy in the near future, this delay is worth factoring into your timeline.
The delay doesn’t mean permanent infertility. Fertility does return for the vast majority of users. But the shot is a poor fit if you want the option to get pregnant quickly after stopping birth control.