Depo-Provera is a convenient and effective form of birth control, but it’s not without its risks. If you’ve been on Depo-Provera for a while, it may be time to switch to another form of birth control such as the pill. There are a number of things you should know before you make the change.

Depo-Provera is a hormonal form of birth control. It’s delivered through a shot and lasts for three months at a time. The shot contains the hormone progestin. This hormone protects against pregnancy by preventing your ovaries from releasing eggs, or ovulating. It also thickens cervical mucus, which can make it more difficult from sperm to reach an egg, should one be released.

This method is up to 99 percent effective when used as directed. This means that if you receive your shot every 12 weeks, you’re protected against pregnancy. If you’re late in getting your shot or otherwise disrupt the release of hormones, it’s about 94 percent effective. If you’re more than 14 days late in getting your shot, your doctor may require you to take a pregnancy test before you can get another shot.

Some women experience the side effects on Depo-Provera. These can include:

  • irregular bleeding
  • lighter or fewer periods
  • a change in sex drive
  • increased appetite
  • weight gain
  • depression
  • increased hair loss or hair growth
  • nausea
  • sore breasts
  • headache

You may also experience bone loss while taking Depo-Provera, especially if you take the drug for two years or more. In 2004, the U.S. Food and Drug Administration issued a boxed label warning indicating Depo-Provera may cause significant bone mineral density loss. The warning cautions that bone loss may not be reversible.

Unlike with other forms of birth control, there’s no way to relieve Depo-Provera’s side effects immediately. If you’re experiencing side effects, they may persist until the hormone is out of your system completely. This means that if you get a shot and begin experiencing side effects, they may continue for up to three months, or when you’re due for your next shot.

Birth control pills are also a form of hormonal birth control. Some brands contain progestin and estrogen, whereas others contain only progestin. They work to prevent pregnancy by stopping ovulation, increasing cervical mucus, and thinning the uterine lining. The pills are taken daily.

When taken at the same time every day, birth control pills are up to 99 percent effective. If you miss a dose or are late taking your pill, they’re 91 percent effective.

Potential side effects will depend on the type of pill you take and how your body reacts to the hormones present. If you choose a progestin-only pill, the side effects may be minimal or similar to what you’re used to experiencing with the Depo-Provera shot.

Common side effects of the pill may include:

  • breakthrough bleeding
  • nausea
  • vomiting
  • tender breasts
  • weight gain
  • mood changes
  • headache

Side effects may lessen or go away over time. Unlike with the Depo-Provera shot, these side effects should stop immediately if you go off of the pill.

Read more: Understanding why missed periods can happen while on birth control »

If you choose a combination pill, you may experience new side effects. This may be because of the estrogen present in the pill. These side effects may include:

  • increased bleeding
  • breast sensitivity
  • decreased appetite
  • cramping
  • headaches
  • vomiting

It’s normal to experience breakthrough bleeding after you first start the pill. If it lasts more than a week or is severe, you should tell your doctor.

Some women may skip periods entirely while on the pill. This is normal. However, you may be pregnant if this happens while you’re sexually active and miss a pill or two or take them late. You should take a pregnancy test and should speak with your doctor about any next steps.

Most side effects disappear within a few pill cycles. You should contact your doctor if your side effects are difficult to cope with or impact your ability to go about your day. Unlike with Depo-Provera, you can stop taking the pill to eliminate side effects at any time.

There are steps you should take when switching from Depo-Provera to the pill if you want to prevent pregnancy.

The most effective way to switch birth control is the “no gap” method. With this method, you go from one type of birth control to another without waiting to get your period.

To do this, there are a few steps that you should follow:

  1. Contact your doctor to verify when you should take your first pill.
  2. Get your first birth control pill pack from your doctor’s office, pharmacy, or local clinic.
  3. Learn the right schedule for taking your pills. Figure out a time to take them each day and put a refill reminder on your calendar.
  4. Take your first birth control pill. Because Depo-Provera remains in your body for up to 15 weeks after your last shot, you can start your first birth control pill at any time within that time frame. Most doctors recommend taking your first pill the day your next shot would be due.

Not every woman should use Depo-Provera or the pill. On rare occasions, both types of birth control have been found to cause blood clots, heart attacks, or strokes. This risk is higher if:

  • you smoke
  • you have a blood-clotting disorder
  • you have a history of blood clots, a heart attack, or a stroke
  • you’re age 35 or over
  • you have diabetes
  • you have high blood pressure
  • you have high cholesterol
  • you have migraines
  • you’re overweight
  • you have breast cancer
  • you’re on long-term bed rest

If you have any of these risk factors, your doctor may advise you not to take the pill.

If you experience severe or sudden symptoms, you should seek immediate medical attention. These symptoms include:

  • abdominal pain
  • chest pain
  • pain in the leg
  • swelling in the leg
  • severe headaches
  • dizziness
  • coughing up blood
  • vision changes
  • shortness of breath
  • slurring your speech
  • weakness
  • numbness in your arms
  • numbness in your legs

If you were on Depo-Provera for two years before switching to the pill, you should talk to your doctor about having a bone scan to detect bone loss.

For many women, a major advantage of Depo-Provera over the pill is that you only have to worry about remembering one shot and one doctor’s appointment for three months. With the pill, you have to remember to take it every day and refill your pill pack each month. If you don’t do this, you may become pregnant.

Before making the switch from Depo-Provera to the pill, think about all available birth control options, their benefits, and drawbacks. Keep in mind your pregnancy goals, medical history, and the potential side effects for each method. If you prefer hormonal birth control that you don’t have to think about often, you may want to consider an intrauterine device (IUD). Your doctor can implant an IUD and it can be left in place for up to 10 years.

Neither form of birth control protects against sexually transmitted infections. You should use a barrier method, such as a male condom, to protect against infection.

For the most part, switching from Depo-Provera to the pill should be simple and effective. Although you may experience some side effects, they’re usually minor. They’re also temporary. Make sure to educate yourself about the symptoms of serious and life-threatening side effects. The faster you get emergency help if they occur, the better your outlook.

Your doctor is the best person to help you plan a birth control switch. They can answer your questions and address your concerns. The most important thing is to choose a method that fits your lifestyle and family-planning needs.