The shot works by releasing progestin hormones over a 3 month period. This thickens cervical mucus which blocks sperm from meeting an egg to fertilize. It also makes it harder for the egg to attach to the uterine wall if it is fertilized, preventing pregnancy once again.

There’s not really much you have to do in order to use the shot—just make sure to keep regular appointments with your health care provider. You just go to the clinic and get an injection. Every three months, you’ll go in for another injection. Easy.
Make sure to discuss the timing of your period and the shot with your provider, because that’ll help determine how soon after the shot you’ll be protected. If you get the shot while you are on your period, it is effective immediately. If you get it while not on your period, it will take the shot 1 week to become effective.
Also, it’s really important to get your shots on time. If you’re more than four weeks late for an injection and have been having unprotected sex, you may have to get a pregnancy test before the next shot.

• Easy to use
• Doesn’t interrupt sex
• Super private—no one will know unless you tell them
• You don’t have to worry about remembering to take birth control every day
• Might give you shorter, lighter periods—or no periods at all
• Your birth control is taken care of for 3 months at a time
• Can be used by women who can’t take estrogen
• It’s very effective at preventing pregnancy—if you get the shots on time
• Safe to use while you’re breastfeeding

Worrying about negative side effects is normal, but for most women, they are not a problem. If you do experience side effects, they should go away over time. As you are introducing hormones into your body, it might take a little time to adjust.

Most common complaints:

• Irregular bleeding, especially for the first 6-12 months (This could mean longer, heavier periods, or spotting in between periods, or your period stopping completely).
• Change in appetite or weight gain (It’s common for some women to gain around 5 pounds in the first year, while other women gain nothing).
• Having to visit the clinic every 13 weeks.
• Delay in returned fertility for a few months after injections are stopped.

Less Common Side Effects:

• Change in sex drive
• Depression
• Hair loss or more hair on your face and body
• Headaches
• Nausea
• Sore Breasts

Remember with the shot, there’s no way to stop the side effects. If you still feel uncomfortable after the course of 2 shots in a row, it might be worth it to switch methods.

Common misunderstandings

• Loss of monthly bleeding is not harmful and does not mean that the blood is “building up” inside the woman.
• Does not make women infertile.
• Even though the shot can delay the return to fertility, it is still important for women to get a shot every 3 months (13 weeks) if they want to effectively prevent pregnancy.
• Getting the shot does not disrupt an existing pregnancy.