What Is the Contraceptive Injection? [Everything You Should Know]

The contraceptive (or birth control) injection is a long-acting, reversible method of contraception that protects against pregnancy. It contains a synthetic version of the hormone progesterone, most commonly depot medroxyprogesterone acetate (DMPA).

You should have the injection every 8-13 weeks, depending on the type.

How Does the Contraceptive Injection Work?

The contraceptive injection prevents pregnancy by releasing progestogen, which:

1. Stops ovulation (egg release).
2. Makes it hard for sperm to reach an egg by thickening cervical mucus.
3. Thins the womb lining, reducing the chance of implantation.

It does not contain oestrogen, making it suitable for people who cannot use combined hormonal contraception (such as the combined pill, contraceptive patch, or vaginal ring).

Read also: Period Care 101: Cycle Stages, Symptoms & Relief Tips.

What Are the Types of Contraceptive Injection?

There are three main types available in the UK:

• Depo-Provera: This type of injection (also called the “Depo injection”) is given every 13 weeks by a doctor or a nurse (you can’t get it by yourself). You usually have it in the bum or upper arm.
• Sayana Press: It is also given every 13 weeks, in your lower tummy or the front of your thigh. You can learn how to do this type of injection by yourself.

How Effective Is the Contraceptive Injection?

When used correctly and given on time, the contraceptive injection is over 99% effective.

With typical use (including delayed or missed injections), the percentage drops to 94% (which is still highly effective).

How Long Does the Contraceptive Injection Take to Work?

It depends on when you have it:

• If given during the first 5 days of your menstrual cycle, it works immediately.
• If given at any other time, you’ll need to use additional contraception (such as condoms) for 7 days.

How Long Does the Contraceptive Injection Last?

Birth control injections usually last from 8 to 13 weeks, depending on the type:

• Depo-Provera & Sayana Press: 13 weeks
• Noristerat: 8 weeks

You should remember to have repeat injections on time. If you’re late, you may need additional protection or emergency contraception, such as the morning-after pill.

Can I Have the Injection After Giving Birth?

Yes, you can have the injection at any time after giving birth, if you’re not breastfeeding.

• If you start on or before day 21 after the birth, you’ll be immediately protected against pregnancy.
• If you start after day 21, you’ll need to use additional protection (such as condoms) for 7 days.

If you are breastfeeding, you can usually start the injection 6 weeks after birth.

Can I Have the Contraceptive Injection After a Miscarriage or Abortion?

Yes, you can.

• If you have the injection immediately after a miscarriage or abortion (within 5 days), you’ll be protected against pregnancy straight away.
• If you have the shot more than 5 days after a miscarriage or abortion, you will need to use additional contraception for a week.

Who Can Get the Injection?

The contraception injection is not suitable for everyone.

You should not use the injection if you:

1. suspect you’re pregnant
2. want to get pregnant in the next year
3. do not want your periods to change (learn all about your period in our guide)
4. have unexplained vaginal bleeding in between periods or after sex
5. have ever had breast cancer, a stroke, or heart disease (by the way, see our guide on heart disease)
6. have ever had a liver condition
7. are at risk of osteoporosis
8. smoke
9. have diabetes
10. have high blood pressure
11. have high cholesterol
12. are living with obesity

Always discuss your medical history with a healthcare professional. If you want to explore your contraception options, take the online contraception assessment Weldricks offers!

What Are the Side Effects of the Contraceptive Injection?

Common contraception injection side effects include:

• Irregular bleeding
• Lighter, heavier, or irregular periods
• Periods stopping altogether
• Possible weight gain (especially if you’re under 18 years old and overweight with a BMI of 30 or over)
• Delayed return to fertility (up to one year after stopping the injection)

While there’s not enough evidence to back the claim, some people also report the following side effects:

• Headaches (see how to relieve headaches)
• Hot flushes
• Mood changes
• Breast tenderness
• Acne (read our guide on the best acne treatments)
• Decreased libido

Risks of Using the Birth Control Injection

There are also some other risks linked to the use of the contraceptive injection. However, the chance of experiencing them is small:

• Bone density reduction: Your bones may become weaker if you use the injection for more than a year. However, your bones will return to normal after stopping the injection.
• Higher risk of cancer: The injection can slightly increase your risk of getting breast or cervical cancer, but the chances are low. And they will become even lower after you stop the injection.
• Allergic reaction
• Skin infection (at the site of the injection)

What Are the Advantages & Disadvantages of the Contraceptive Injection?

Advantages

1. Over 99% effective
2. Does not interrupt sex
3. Does not contain oestrogen (ideal for individuals who cannot use contraception containing oestrogen, such as the combined pill or vaginal ring)
4. May help with period pain and heavy periods
5. No need to remember to take a pill every day
6. Not visible
7. Long-lasting
8. Not affected by other medication or episodes of vomiting or diarrhoea

Disadvantages

1. Does not protect against STIs
2. Delayed return to fertility (can take up to a year)
3. Irregular bleeding, especially in the first year
4. May cause side effects (weight gain, irregular periods, etc.)
5. Requires clinic visits
6. Cannot be removed once given (must wait for it to wear off)

Is the Contraceptive Injection Safe?

Yes, for most people, it is considered safe and effective. However, you should consult your GP before you start the injections to ensure you’re suitable.

Where Can I Get the Contraception Injection?

In the UK, the contraceptive injection is available from:

• GP surgeries
• Sexual health clinics (also called family planning or contraception clinics)

All about the Contraceptive Injection — Conclusion

The injection is a reliable, long-acting method of contraception that suits many people who want to prevent pregnancy in a discreet and convenient way.

However, it may not be right for everyone. That’s why you should always consult your GP before starting the injections.

Interested in learning more about contraception? Then don’t miss our expert guides:

• Can the Pill Make You Infertile? [What Science Says]
• What’s the Best Contraceptive Pill For Over 40s & 50s? [Expert Guide]
• Does The Contraceptive Pill Stop Periods? [FAQs Answered]
• When Can I Start Taking The Contraceptive Pill?