Using contraceptive implants and injections may have some disadvantages, which you should consider carefully before deciding on the right method of contraception for you.
The contraceptive implant or injection will not protect you against sexually transmitted infections (STIs), so you may still have to use another form of contraception, such as condoms.
Contraceptive implant
Disrupted periods
Your periods may change significantly in the first year of using a contraceptive implant. You will usually have irregular periods and may have heavy periods, shorter and lighter periods, or your periods may stop altogether. These changes may settle down after the first year of using implants, but they can sometimes continue as long as the implant is fitted.
Although these changes are not harmful, they may not be acceptable for some women. Your GP may be able to help by providing additional medication if you have prolonged bleeding.
Other side effects
Some women using the contraceptive implant also report:
These side effects usually stop after the first few months. If you have prolonged or severe headaches or other side effects, tell your doctor.
In rare cases, the area of skin where the implant has been fitted can become infected. If this happens, the area will be cleaned and may be treated with antibiotics.
Contraceptive injections
It can take up to 12 weeks for injected progestogen to leave the body. Therefore, if you have any side effects, they may continue during this time and for some time afterwards.
Disrupted periods
Your periods may change significantly during the first year of using contraceptive injections. They will usually become irregular and may be very heavy, shorter and lighter, or stop altogether. This may settle down after the first year, but may continue as long as the injected progestogen remains in your body.
It can take a while for your periods and natural fertility to return after you stop using the injection. It takes around 8 to 12 weeks for injected progestogen to leave the body, but you may have to wait longer for your periods to return to normal if you are trying to get pregnant.
Until you are ovulating regularly each month, it can be difficult to work out when you are at your most fertile. In some cases, it can take three months to a year for your periods to return to normal.
Weight gain
You may put on weight when you use contraceptive injections, although some women lose weight. Use of the injections may be associated with an increase in weight of up to 2–3kg over one year.
Bone risk
Using contraceptive injections can cause thinning of the bones, but it does not increase your risk of bone fracture. Your bone replaces itself when you stop taking the injection, so it does not appear to cause any long-term problems. If you are at risk of developing osteoporosis, you will usually be advised to use another method of contraception.
Other side effects
Some women using contraceptive injections also report:
There is also a small risk of infection at the site of the injection. In very rare cases, some people may have an allergic reaction to the injection.
