Hormonal injection for birth control works by suppressing the egg from coming out of the ovary every month (ovulation). Protection begins immediately after the first shot if given during a menstrual period. They are 99% effective in preventing birth.
However, it is not recommended for women who have:
- unexplained vaginal bleeding
- liver disease
- breast cancer
- chest pains, stroke or heart attack
- suspicion of being pregnant
Side effects include:
- Irregular menstrual periods or no periods
- Acne (pimples)
- Changes in appetite
- Weight gain
- Excessive growth of facial and body hair
- Hair loss
Some women may not get pregnant after stopping the injections. It may take up to 2 years to conceive.
You need to stop taking hormone shots several months ahead of time if you plan to become pregnant.