Depo-Provera is the brand name of the birth control shot. It’s an injectable form of the drug depot medroxyprogesterone acetate, or DMPA for short. DMPA is a man-made version of progestin, a type of hormone.

DMPA was approved by the U.S. Food and Drug Administration in 1992. It’s highly effective at preventing pregnancy. It’s also very convenient — one shot lasts for three months.

DMPA blocks ovulation, the release of an egg from the ovaries. Without ovulation, pregnancy can’t occur. DMPA also thickens cervical mucus to block sperm.

Each shot lasts for 13 weeks. After that, you must get a new shot to continue preventing pregnancy. It’s important to schedule your appointment to get the shot well before your last shot is due to expire.

If you don’t receive the next shot in time, you risk becoming pregnant because of decreased levels of the drug in your body. If you can’t get your next shot on time, you should use a backup method of birth control.

The shot is generally not recommended for use longer than two years, unless you’re not able to use other methods of birth control.

Your doctor needs to confirm that it’s safe for you to receive the shot. You can make an appointment to receive it after your doctor’s confirmation as long as you’re reasonably sure you’re not pregnant. Your doctor will usually give the shot in your upper arm or buttocks, whichever you prefer.

If you get the shot within five days of starting your period or within five days of giving birth, you’re protected immediately. Otherwise, you need to use a backup birth control method for the first week.

You’ll need to return to your doctor’s office every three months for another injection. If 14 weeks or more have passed since your last shot, your doctor may perform a pregnancy test before giving you another shot.

The Depo-Provera shot is a highly effective birth control method. Those who use it correctly have a risk of pregnancy that’s less than 1 percent. However, this percentage increases when you don’t receive the shot at the recommended times.

Most women taking the shot have progressively lighter periods. Your period may even end up stopping entirely after you’ve received the shot for a year or longer. This is perfectly safe. Others may get longer, heavier periods.

Other common side effects include:

  • headaches
  • abdominal pain
  • dizziness
  • nervousness
  • decrease in sex drive
  • weight gain, which can be more common the longer you use it

Less common side effects of the shot include:

  • acne
  • bloating
  • hot flushes
  • insomnia
  • achy joints
  • nausea
  • sore breasts
  • hair loss
  • depression

Women who use Depo-Provera may also experience decreased bone density. This happens more the longer you use it and stops when you stop using the shot.

You’ll recover some bone mineral density after you stop using the shot, but you may not have full recovery. Your doctor may recommend you take calcium supplements and eat foods rich in calcium and vitamin D to help protect your bones.

Serious side effects

Though rare, serious side effects can occur. You should seek immediate medical attention if you start having the following symptoms while you’re on the birth control shot:

  • major depression
  • pus or pain near the injection site
  • unusual or prolonged vaginal bleeding
  • yellowing of your skin or the whites of your eyes
  • breast lumps
  • migraines with aura, which is a bright, flashing sensation that precedes migraine pain

The primary benefit of the birth control shot is its simplicity. However, there are also some drawbacks to this method.

Pros

  • You only have to think about birth control once every three months.
  • There’s less opportunity for you to forget or miss a dose.
  • It can be used by those who can’t take estrogen, which isn’t true for many other types of hormone contraception methods.

Cons

  • It doesn’t protect against sexually transmitted infections.
  • You may have spotting between periods.
  • Your periods may become irregular.
  • You have to remember to schedule an appointment to get a shot every three months.
  • It’s usually not recommended for long-term use.

If you’re considering options for birth control, talk with your doctor. They can help you balance the facts about each option with your health history and lifestyle considerations to help determine which method is best for you.