Depo-Provera: How effective is the birth control shot?

The birth control shot has created quite a buzz in the last couple of decades as one of the most effective forms of hormonal birth control methods currently available. It boasts a 99% effectiveness rate with perfect use and a 96% rate with typical use (more on those metrics below). 

Aside from being highly effective, the birth control shot’s appeal also comes from the fact that you only need to get it once every 13 weeks, or about 4 times per year. You can essentially “get it and forget it,” as long as you have your appointments regularly booked. But let’s rewind a second and start with the basics:

What is the birth control shot?

The birth control shot is a form of contraception that involves an injection of hormones every 8 to 13 weeks to prevent pregnancy. You may also see it referred to as the Medroxyprogesterone acetate (MPA) injection by the medical community, and “the depo shot” or Depo-Provera (its brand name) informally.

The shot is known as a medium-term contraceptive. It is longer lasting than short-term birth control methods like condoms, but it is a shorter-term solution compared to intrauterine devices (IUDs) and implants, as it is generally not recommended to get the shot for more than two years at a time. [1] The shot is also a more temporary option as you don’t need to get anything removed if you choose to stop using it, the effects will eventually wear off. 

How does the birth control shot work?

The birth control shot contains progestin, a synthetic version of the natural hormone progesterone. Progestin prevents ovulation, which implies you cannot conceive. It also thickens your cervical mucus, making it difficult for sperm to get through. These two combined processes make the birth control shot highly effective at preventing pregnancy. [2]

While you can start the shot at any time during your cycle, you’ll be protected from pregnancy right away if you receive it:

• Within the first 7 days of your cycle after starting your period
• Within 7 days after an early pregnancy has terminated
• Within 3 weeks after giving birth

This is because the shot has time to take effect before you ovulate again. If you get the shot outside of these timeframes, you’ll need to use a backup form of birth control like condoms for one week to make sure you’re fully protected while the shot takes effect. 

One of the most important things to remember about the birth control shot is that the dosage wears off in your body. If you do not get your next shot within the 8 to 13 week window following the initial shot, you won’t be properly protected from pregnancy anymore. [3]

What is Depo-Provera?

Depo-Provera is the brand name of the most common birth control shot available in the United States. It’s also referred to as DMPA or the depo shot, but when people use the term “the birth control shot,” they’re referring to Depo-Provera most of the time.

How effective is Depo-Provera?

When the health community evaluates the rate of “effectiveness” of a birth control method, it is described in terms of “perfect” and “typical” use. Perfect use refers to how effective a birth control method is at preventing pregnancy if it’s used perfectly as recommended every single time. Typical use refers to the way a contraception is used in the real world, including human error, e.g. missing an appointment and getting the shot later than intended.

With that in mind, the birth control shot is considered highly effective with perfect use, showing a 99.8% effectiveness rate. If we think about this percentage in terms of actual people, that means that out of 100 people using the birth control shot perfectly for a year, less than one will get pregnant.

However, the birth control shot is 96% effective with typical use, meaning that four out of every 100 people getting the shot for a year will get pregnant. [4]

For the shot specifically, the potential for human error increases if the injection isn’t administered on time, so if you do choose to go on Depo-Provera, make sure that you and your doctor are on the same page about keeping your four shot appointments each year at the right time for continuous contraception.

Who should get Depo-Provera?

The Depo-Provera birth control shot is typically recommended if you feel that taking a daily contraception pill doesn’t fit into your lifestyle, if you do not plan to become pregnant for the next two years, and if you do not want a longer term birth control method like an IUD or implant. If you have certain health conditions like endometriosis, the shot is also a great option due to its lack of estrogen.

It’s a good choice for nursing mothers as well. According to Planned Parenthood, the shot is safe when nursing and won’t affect your baby or the amount of milk you produce. [3] However, it’s worth noting that the manufacturer of Depo-Provera recommends waiting until 6 weeks after childbirth to receive your first injection if you are nursing exclusively. [5]

Make sure to consider your unique lifestyle factors and preferences, such as cost and side effects, as well when researching contraception methods like the birth control shot.

Benefits of birth control shot

Aside from your individual needs and preferences, there are a few advantages across the board when it comes to the shot [3]:

• Get it and forget it: Unlike the pill, you don’t need to think about your birth control daily with the shot. You also won’t have to worry about your dosage (your doctor handles that).
• Less PMS: The shot can reduce premenstrual symptoms and pain, and may even lighten or stop your period altogether. 
• No interruptions: The shot doesn’t interrupt sex like condoms sometimes can.

What are the disadvantages of the birth control shot?

With that in mind, the shot definitely isn’t right for everyone looking for hormonal contraception methods. Here are a few Depo-Provera side effects and drawbacks you need to consider if you’re thinking about starting the birth control shot:

No STI protection

The shot does not protect against sexually transmitted infections (STIs), which can be serious and lead to worse overall health issues. If you want maximum protection from both pregnancy and getting/spreading STIs, it’s recommended to use a condom in conjunction with the shot. [3]

Personal health

There are also medical side effects associated with the shot that can affect your short and long term health:

• Bone Density: The shot has been known to decrease bone density over time, which is why most doctors recommend only getting the shot for a period of two years or less to avoid unnecessary damage. If you’re in your teens or early 20’s, your doctor may be especially hesitant to recommend the shot as these are formative years for bone density development. If you can’t use other methods of birth control and need to be on the shot at this age and/or for longer than two years, it’s recommended to take calcium and vitamin D supplements to help prevent bone density issues. [5]
• Hormone Fluctuations: Like most hormonal birth control methods, there are Depo-Provera side effects that are caused by synthetic hormone intake. These include weight gain, nausea, headaches, tender breasts, mood swings, and changes to the flow and frequency of your period. The progestin in the birth control shot can also worsen migraine, depression, or epilepsy. [5] All of these side effects can last up to the full course of the first shot (13 weeks), although they may go away faster. [3]
• Family History: Your doctor might not recommend the shot if you have a personal or family history of breast cancer, liver disease, asthma, heart disease, or allergies to ingredients in the shot. If you have high blood pressure or diabetes, your doctor will want to monitor your symptoms and reaction to the shot very closely. This is all because the shot, along with other forms of hormonal birth control, can affect blood pressure and glucose tolerance. [5]

Timeline

As mentioned previously, you’ll need to be diligent about making and keeping your scheduled injection appointments with your doctor in order to maintain the effectiveness of the Depo-Provera shot. If you travel or move frequently, or have other priorities that cause you to reschedule appointments often, the shot may not fit into your lifestyle.

Furthermore, it can take up to 10 months for your system to regulate after your last shot. If you make the decision that you want to get pregnant, this may push your timeline out by nearly a year. [3] If you’re planning on getting pregnant soon after you stop using birth control, you should consider another method such as Natural Cycles to help you plan your pregnancy when the time is right.

When to see a doctor

Reach out to your healthcare provider as soon as possible if you have any of the underlying conditions mentioned above (migraine, depression, or epilepsy) and you notice a change in symptoms after getting the shot. You should also see a doctor if you’ve gotten the shot and you notice [1]:

• Itching, hives, or difficulty breathing
• Pain and/or pus at the injection site
• Worsening depression
• Jaundice
• Sharp pain in your chest and blood in your cough
• Lump in the breast or chest
• Pain and/or swelling in your lower leg
• Severe abdominal pain on one side
• Unusual or prolonged vaginal bleeding (besides light bleeding or spotting between periods, which is normal)
• Stroke symptoms such as sudden dizziness, fainting, vomiting, trouble seeing or speaking, and numbness in the limbs 

Aside from these extreme reactions, it’s best to share any side effects you experience with your doctor, especially those that affect your daily life. They can provide guidance on managing symptoms or switching contraception methods if necessary in accordance with your personal health history and lifestyle.

With all of this in mind, if the birth control shot sounds like the best method for you, reach out to your healthcare provider and make an appointment to explore this contraception option. They’ll likely ask all the lifestyle questions outlined in this article, along with questions about other types of birth control you’ve used and how you reacted in the past, your current menstrual cycle, and the possibility of pregnancy. This is all with your best interest in mind, making sure it’s safe for you to receive the birth control shot.

Natural Cycles as an alternative

Looking for a non-hormonal birth control method? Natural Cycles may be the best choice for you. Remember our “perfect” and “typical” use effectiveness measurement from earlier? Natural Cycles is 98% effective with perfect use and 93% effective with typical use.

It’s also the first FDA Cleared birth control app available in the United States. By monitoring your basal body temperature via an algorithm that learns your unique patterns, it helps you become aware of your natural fertile window. To prevent pregnancy, avoid sex or use condoms during those fertile days. To get pregnant, take advantage of this knowledge and time sex around ovulation.

If the birth control shot or other hormonal methods of contraception don't seem right for you, check out Natural Cycles.