Depo Shot: Birth Control Injection Guide & Side Effects

What Is the Depo Shot and How Does It Work?

The Depo shot is an injectable contraceptive containing depot medroxyprogesterone acetate (DMPA), a synthetic progestogen hormone. It prevents pregnancy primarily by stopping ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining. Each injection provides 12-13 weeks of highly effective birth control protection.

The Depo shot, commonly known by its brand name Depo-Provera, is one of the most effective reversible contraceptive methods available when used correctly. It contains 150mg of depot medroxyprogesterone acetate (DMPA), a long-acting progestogen that is slowly released into the bloodstream over approximately three months. This sustained-release mechanism is what gives the injection its long-lasting contraceptive effect and eliminates the need for daily or weekly intervention.

When you receive the Depo shot, the hormone is injected deep into the muscle tissue of your buttock or upper arm. From there, the medication forms a "depot" or reservoir that gradually releases the hormone into your bloodstream. Peak serum concentrations are reached within about three weeks after injection, and contraceptive effectiveness is maintained for at least 12-13 weeks. This pharmacokinetic profile makes the Depo shot particularly reliable because it doesn't depend on user compliance like daily pills.

The progestogen in the Depo shot works through multiple mechanisms to prevent pregnancy. First and most importantly, it suppresses the hormonal signals from your pituitary gland that normally trigger ovulation. Without ovulation, there is no egg available for fertilization. Additionally, the hormone causes changes in the cervical mucus, making it thick and sticky, which creates a physical barrier that sperm cannot easily penetrate. Finally, DMPA thins the uterine lining (endometrium), which would make implantation difficult even if fertilization somehow occurred.

Progestogen-only versus combined contraceptives

Unlike combined hormonal contraceptives that contain both estrogen and progestogen, the Depo shot is a progestogen-only method. This makes it suitable for many women who cannot use estrogen-containing contraceptives, including those who are breastfeeding, those with certain cardiovascular risk factors, and those who experience estrogen-related side effects like migraines with aura. The absence of estrogen is also why the Depo shot affects menstrual patterns differently than combined pills.

The progestogen-only nature of the injection means it doesn't carry the same risks associated with estrogen, such as increased risk of blood clots in otherwise healthy young women. However, it does have its own unique considerations, particularly regarding bone mineral density and the potential for irregular bleeding, which we will discuss in detail later in this article.

How the Depo shot differs from other contraceptives

Compared to other hormonal contraceptives, the Depo shot offers several distinct characteristics. Unlike daily pills, you don't need to remember to take anything at home. Unlike the contraceptive implant or IUD, no device needs to be inserted into your body. Unlike the patch or ring, there's nothing visible or that could fall out during activities. The trade-off is that you need to return to a healthcare provider four times per year for your injections, and once injected, the hormone cannot be removed from your system if you experience side effects.

How Effective Is the Depo Shot at Preventing Pregnancy?

The Depo shot is over 99% effective with perfect use, meaning less than 1 in 100 women will become pregnant in a year. With typical use (accounting for late or missed injections), effectiveness is about 94%, meaning about 6 in 100 women will become pregnant annually. The key to maintaining effectiveness is getting injections on time every 12-13 weeks.

When discussing contraceptive effectiveness, it's essential to understand the difference between "perfect use" and "typical use" rates. Perfect use refers to the effectiveness when the method is used exactly as directed, without any errors or delays. Typical use reflects real-world effectiveness, accounting for the mistakes and inconsistencies that naturally occur in everyday life. For the Depo shot, this distinction primarily relates to whether injections are received on schedule.

With perfect use, the Depo shot has a failure rate of only 0.2%, making it one of the most effective reversible contraceptive methods available. This means that if 1,000 women used the injection perfectly for one year, only about 2 would become pregnant. This effectiveness rate is comparable to that of contraceptive implants and IUDs, which are considered the gold standard for reversible contraception.

However, typical use effectiveness drops to about 94%, with approximately 6 out of 100 women becoming pregnant each year. The main reason for this gap is late or missed injections. The hormone levels from a Depo shot remain effective for about 12-13 weeks, but after that window, protection begins to decline. If you're more than two weeks late for your injection (beyond 15 weeks from your last shot), you may need to use backup contraception and potentially take a pregnancy test before receiving your next injection.

Factors that can reduce effectiveness

Several factors can potentially affect the effectiveness of the Depo shot. Late injections are the most common cause of contraceptive failure. Certain medications, particularly some anticonvulsants and rifampicin (an antibiotic used for tuberculosis), can increase the metabolism of progestogens and potentially reduce effectiveness. If you're taking any of these medications, discuss alternative contraceptive options with your healthcare provider.

Unlike oral contraceptives, the effectiveness of the Depo shot is not affected by vomiting or diarrhea, since the hormone is absorbed directly into the muscle rather than through the digestive system. This can be a significant advantage for women who experience gastrointestinal issues or who have conditions that affect nutrient absorption.

How Do You Get the Depo Shot?

To get the Depo shot, schedule an appointment with a healthcare provider such as a gynecologist, family planning clinic, or primary care physician. After a medical assessment, you'll receive the injection in your buttock or upper arm. If given within the first 5 days of your period, it's immediately effective; otherwise, use backup contraception for 7 days. Return every 12-13 weeks for subsequent injections.

Getting started with the Depo shot involves a consultation with a qualified healthcare provider who can assess whether this contraceptive method is appropriate for you. This can be done at various healthcare settings including gynecology offices, family planning clinics, sexual health clinics, or with your primary care physician. Many clinics offer same-day starts, meaning you can receive your first injection during your initial consultation if you're deemed a suitable candidate.

During your consultation, your healthcare provider will review your medical history to check for any contraindications or conditions that might make the Depo shot less suitable for you. They will typically check your blood pressure and may ask about your menstrual history, any medications you're taking, and your future pregnancy plans. This is an important conversation because the Depo shot's effect on fertility return makes it less ideal for those planning to conceive within the next one to two years.

The injection itself is quick and relatively simple. The standard Depo-Provera injection (150mg) is given intramuscularly, usually into the gluteal muscle (buttock) or the deltoid muscle (upper arm). The healthcare provider will clean the injection site with an antiseptic, then insert the needle and slowly inject the medication. Most women describe the sensation as similar to other vaccinations—a brief pinch followed by some mild soreness at the injection site for a day or two.

Timing of the first injection

The timing of your first Depo shot is important for immediate protection. If you receive the injection within the first five days of your menstrual period, you're protected against pregnancy immediately. If you start at any other time in your cycle, you'll need to use additional contraception (such as condoms) or abstain from intercourse for seven days while the injection takes effect. Your provider may also recommend a pregnancy test before starting if there's any possibility you could already be pregnant.

If you're switching from another contraceptive method, the timing recommendations vary. Generally, you can receive your first Depo shot while still using your previous method, then discontinue the old method once the injection becomes effective. Your healthcare provider can give you specific guidance based on what method you're switching from.

Self-administration options

A subcutaneous formulation of DMPA (Depo-SubQ Provera 104, containing 104mg of medroxyprogesterone acetate) is available in some countries and can be self-administered at home after proper training from a healthcare provider. This version is injected into the fatty tissue just under the skin of the thigh or abdomen, rather than deep into the muscle. Self-injection can offer greater convenience and autonomy, though you'll still need regular contact with healthcare services for prescription refills and periodic health assessments.

Who Is the Depo Shot Suitable For?

The Depo shot is suitable for most women seeking long-acting, reversible contraception who prefer not to take daily pills or have devices inserted. It's particularly appropriate for women who cannot use estrogen, are breastfeeding, or need a discreet method. However, it's not a first-choice option for those under 23 (due to bone concerns) or those planning pregnancy within 1-2 years.

The Depo shot can be an excellent contraceptive choice for many women, but it's particularly well-suited for certain situations. Understanding whether it aligns with your health profile, lifestyle, and reproductive goals is essential for making an informed decision. Here we'll explore who typically benefits most from this method and who might want to consider alternatives.

Women who have difficulty remembering to take daily pills often find the Depo shot liberating. With only four appointments per year, the mental burden of contraception is significantly reduced. This can be especially valuable for those with busy, irregular schedules, or for women who have experienced unintended pregnancies due to missed pills in the past. The "set it and forget it" nature of the injection (for three months at a time) provides peace of mind.

The Depo shot is also particularly appropriate for women who cannot use estrogen-containing contraceptives. This includes women who are breastfeeding (progestogen-only methods don't affect milk supply like estrogen can), women with a history of blood clots or certain cardiovascular risk factors, women who experience migraines with aura, and women over 35 who smoke. The World Health Organization classifies the Depo shot as generally safe (Category 1 or 2) for most of these situations where combined hormonal contraceptives would be contraindicated.

Advantages for specific situations

The Depo shot offers particular advantages in certain circumstances. For women with heavy or painful periods, the injection often reduces menstrual bleeding significantly and may eliminate periods entirely after several months of use. This can dramatically improve quality of life for those who suffer from conditions like endometriosis or heavy menstrual bleeding. Some women specifically choose the Depo shot because they prefer not to have monthly periods.

Women who need a discreet contraceptive method may also prefer the Depo shot. Unlike pills that must be taken daily, patches that are visible on the skin, or rings that a partner might feel, the injection leaves no trace. This can be important in situations where contraceptive use needs to remain private, though ideally all women should be able to make reproductive choices freely and safely.

Who should consider alternatives

Despite its benefits, the Depo shot isn't the optimal choice for everyone. Due to its potential effects on bone mineral density, current guidelines suggest it should not be a first-line contraceptive choice for adolescents and young women under 23 years old, as this is the critical period for building peak bone mass. While bone density typically recovers after stopping the injection, the concern is that starting with lower peak bone mass could increase osteoporosis risk later in life.

Women who want to become pregnant within the next one to two years should also consider alternative methods. Unlike most other contraceptives where fertility returns almost immediately upon stopping, the Depo shot can delay fertility return for 6 to 18 months after the last injection, and occasionally longer. If having a child in the near future is part of your plans, a shorter-acting method might be more appropriate.

What Are the Side Effects of the Depo Shot?

Common side effects of the Depo shot include irregular bleeding or spotting (especially in the first few months), weight gain (average 2-4 kg over two years), headaches, mood changes, and decreased sex drive. Many users eventually experience amenorrhea (no periods). The injection can also temporarily reduce bone mineral density, though this typically recovers after stopping.

Like all medications, the Depo shot can cause side effects, though not everyone experiences them and they often improve over time. Understanding what to expect can help you make an informed decision and know when to seek advice from your healthcare provider. The most common side effects relate to changes in menstrual bleeding patterns, which affect the majority of users to some degree.

Irregular bleeding is the most frequently reported side effect, particularly during the first few months of use. This can manifest as spotting between periods, longer periods, shorter periods, or unpredictable bleeding patterns. The bleeding is typically light and not harmful, but it can be inconvenient and frustrating. The good news is that bleeding irregularities usually improve with continued use, and many women progress to having very light periods or no periods at all.

After about one year of Depo shot use, approximately 50% of women experience amenorrhea (complete absence of menstrual periods). This percentage increases to about 70% after two years of use. While some women find this absence of periods to be a welcome benefit, others may find it disconcerting or worry about pregnancy. If you've been receiving your injections on time, amenorrhea is a normal and expected effect of the medication, not a sign of pregnancy.

Weight changes

Weight gain is a commonly discussed potential side effect of the Depo shot, though the evidence is mixed. Research suggests that some users do gain weight, with studies showing an average gain of about 2-4 kilograms (4-9 pounds) over two years of use. However, this varies considerably between individuals—some women gain more, some less, and some don't gain any weight at all. The mechanism isn't fully understood but may relate to increased appetite or changes in metabolism.

It's worth noting that many women gain weight over time regardless of contraceptive use, making it difficult to attribute weight changes specifically to the Depo shot. If you're concerned about weight, monitoring your weight after starting the injection and maintaining healthy eating and exercise habits can help you identify and address any changes early.

Bone mineral density effects

One of the most significant considerations with the Depo shot is its effect on bone mineral density (BMD). Studies have consistently shown that DMPA use is associated with a decrease in BMD, particularly in the spine and hip. This occurs because the low estrogen levels caused by the injection reduce calcium absorption and bone formation. The decrease in BMD appears to be greatest during the first two years of use and then stabilizes.

Importantly, research also shows that bone mineral density typically recovers after stopping the Depo shot, though recovery may be slower in older women. Current guidelines suggest that for most women, the benefits of the Depo shot outweigh the risks, but providers may recommend calcium and vitamin D supplementation during use and discuss the duration of use, particularly for long-term users and those with other osteoporosis risk factors.

Other potential side effects

Other side effects that some women experience include headaches, mood changes (including depression in some cases), decreased libido, breast tenderness, acne, and hair changes. Some women report experiencing symptoms similar to premenstrual syndrome. Injection site reactions such as pain, redness, or a small lump at the injection site are also possible but usually mild and temporary.

• Headaches: May occur, especially in the first few months; usually mild and manageable
• Mood changes: Some women report mood swings, anxiety, or depression; discuss with your provider if significant
• Decreased sex drive: Reported by some users; may improve over time or after stopping
• Acne: Can improve or worsen depending on the individual
• Breast tenderness: Usually mild and often improves with continued use

How Long Does It Take to Get Pregnant After Stopping the Depo Shot?

Fertility typically returns 6 to 18 months after the last Depo shot injection, though it can occasionally take up to 2 years. This delay occurs because the hormone must completely clear from your system before ovulation resumes. The average time to conception after stopping is about 10 months from the last injection. If planning pregnancy soon, consider switching to a shorter-acting method in advance.

The delayed return to fertility is one of the most important factors to consider when choosing the Depo shot as your contraceptive method. Unlike most other reversible contraceptives, where fertility returns almost immediately upon discontinuation, the Depo shot's effects persist in the body for a significant period after the last injection. This is because the hormone stored in the injection site continues to be released slowly, even after the contraceptive effect has worn off.

On average, ovulation returns about 5-6 months after the last injection was due (not after the last injection was given), but there is considerable individual variation. Some women regain fertility within a few months, while others may take up to 18-24 months. Studies show that the median time to conception after discontinuing the Depo shot is approximately 10 months from the date of the last injection. By 12 months after the last injection, about 50% of women who wish to conceive have become pregnant, and by 18 months, this increases to about 90%.

The duration of Depo shot use does not appear to significantly affect how long it takes for fertility to return. Whether you've used the injection for one year or five years, the delay in fertility return is similar. What matters most is how your individual body metabolizes and clears the hormone. Factors like body weight and metabolic rate may play a role, though this isn't fully understood.

Planning for pregnancy

If you're considering becoming pregnant in the foreseeable future, it's important to factor in this delayed fertility return when making your contraceptive choices. If you want to conceive within the next one to two years, the Depo shot may not be the most practical choice. Instead, consider a method with a quicker return to fertility, such as the combined pill, the mini-pill, the contraceptive patch, or barrier methods like condoms.

If you're currently using the Depo shot and decide you want to become pregnant, you have a few options. You can simply stop getting injections and wait for fertility to return naturally, which is the simplest approach. Alternatively, if you want to start trying sooner, you could switch to a shorter-acting method for a transitional period while the DMPA clears from your system, though this doesn't speed up the process—it just provides contraception during the waiting period if you change your mind.

What Are the Advantages and Disadvantages?

Advantages of the Depo shot include high effectiveness, no daily routine required, suitability for those who cannot use estrogen, and potential reduction or elimination of periods. Disadvantages include the need for regular clinic visits, potential for irregular bleeding, possible weight gain, delayed fertility return, bone density concerns, and inability to remove the hormone once injected if side effects occur.

Making an informed decision about contraception requires weighing the pros and cons in the context of your individual circumstances, preferences, and health profile. The Depo shot has significant advantages that make it an excellent choice for some women, while its disadvantages make it less suitable for others. Let's examine both sides in detail.

Advantages of the Depo shot

High effectiveness: With perfect use, the Depo shot is over 99% effective, making it one of the most reliable reversible contraceptives available. Even with typical use, it's about 94% effective, which is comparable to or better than many other user-dependent methods.

Convenience: With only four injections per year, you don't need to think about contraception on a daily or even weekly basis. This can significantly reduce the mental load associated with birth control and is ideal for those with busy or unpredictable schedules.

Privacy: The injection leaves no visible signs and nothing that needs to be stored at home or carried with you. This makes it a discreet option for those who need or prefer privacy regarding their contraceptive use.

Estrogen-free: As a progestogen-only method, the Depo shot is suitable for women who cannot use estrogen due to medical contraindications or side effects. This includes breastfeeding women, those with certain cardiovascular risk factors, and those who experience estrogen-related migraines.

May reduce periods: Many users experience lighter periods or no periods at all after several months of use. For women who suffer from heavy, painful, or inconvenient menstruation, this can be a significant quality-of-life improvement.

Not affected by GI issues: Unlike oral contraceptives, the Depo shot's effectiveness isn't compromised by vomiting or diarrhea, since it's absorbed directly through the muscle rather than the digestive system.

Disadvantages of the Depo shot

Requires clinic visits: You must visit a healthcare provider four times per year for your injections. This can be inconvenient for those with limited access to healthcare, inflexible work schedules, or transportation challenges.

Cannot be reversed once given: Once you receive the injection, the hormone is in your system for approximately three months. If you experience unpleasant side effects, you cannot simply stop taking the medication like you could with pills—you have to wait for the hormone to naturally clear from your body.

Irregular bleeding: Particularly in the first few months, many users experience unpredictable spotting or bleeding, which can be inconvenient and frustrating, even though it's not harmful.

Delayed fertility return: The 6-18 month delay in fertility return after stopping makes the Depo shot unsuitable for those who may want to become pregnant in the near future.

Bone density effects: The temporary reduction in bone mineral density is a concern, particularly for long-term users and those at higher risk for osteoporosis. This is why it's not recommended as a first-line choice for those under 23.

Potential weight gain: While not universal, some users do experience weight gain that they attribute to the injection.

No STI protection: Like most hormonal contraceptives, the Depo shot does not protect against sexually transmitted infections. Condoms should be used for STI prevention.

Frequently Asked Questions