Contraception side effects: what to expect from implants, injections and pills

Hormonal methods release progestogen or a combination of hormones, which changes the lining of the womb and the pattern of bleeding. That is the main reason period changes are the commonest effect reported for the methods described here.

The NHS stresses that the contraceptive implant is very safe and serious side effects and complications are rare. Side effects that are common are generally not dangerous but can be a reason people stop a method, so knowing what to expect helps people decide.

This page covers methods for which NHS side-effect pages were read: the implant, the injection and the progestogen-only pill. Other methods, including the combined pill, coils, patches and rings, have their own risks and are described on the NHS contraception pages and by a GP or sexual health clinic.

The NHS says it is very common to have a change in your periods after the implant is fitted. Changes are not usually anything to worry about, but if they become a problem, contact a GP or sexual health clinic.

• Periods may be lighter, less regular with light bleeding (spotting) between periods, heavier or more painful, longer, or stop completely.

• Periods may be unpredictable, for example a heavy period followed by a very light period, or a missed period.

• Other reported effects include headache, sore breasts, weight gain, acne, and thrush or bacterial vaginosis, though the NHS says there is not enough evidence to say whether the implant causes them.

• Risks include infection where the implant is put in, leading to swelling and pain, and the implant moving out of place, usually a few centimetres away from where it was put in.

• Rarer, more serious risks include a blood clot, and ectopic pregnancy in the rare case that the implant fails.

The NHS lists the common side effects of the contraceptive injection as changes to periods, such as periods stopping, being irregular or lasting longer, with the likelihood of periods stopping completely increasing the longer you use it, along with putting on weight, and pain, a small lump or a scar where the injection is done.

Some people report acne, lower sex drive, mood changes, hot flushes and headaches, but the NHS says there is not enough evidence to say if the injection causes these.

The NHS says the progestogen-only pill has few side effects, but it may change your periods in different ways: they may be lighter, more frequent or may stop altogether, and you may get some bleeding between periods.

Some people get acne, mood swings, weight gain or changes to sex drive, but the NHS says there is not enough evidence to say whether these are caused by the pill. Speak to a pharmacist or doctor if side effects are a problem.

There is a chance of developing ovarian cysts, which the NHS says are not dangerous and do not usually need to be removed, and often disappear without treatment. There may be a possible link with breast cancer, but the evidence is limited and if there is any increased chance the risk is still very small.

Contact a GP or sexual health clinic if period changes become a problem, if you think the implant site is infected, or if you think the implant has moved. The NHS says to contact a GP or sexual health clinic if you think you have an infection or the implant has moved out of place.

Symptoms of a blood clot, such as a painful, swollen leg or sudden breathlessness or chest pain, need urgent medical help, as do severe one-sided lower tummy pain with a missed period or sudden faintness, which could be an ectopic pregnancy. The NHS lists ectopic pregnancy as a rare risk if the implant fails.

The NHS suggests finding out about choosing a method of contraception, including the side effects and risks of different methods. Sexual health clinics, GP surgeries and some pharmacies can discuss options.

Side effects that are common early on, such as changes to bleeding, can settle over time, but the NHS says if they are a problem you do not have to put up with them. Keep a record of bleeding and symptoms to help the clinician understand what is happening, and do not stop a method without arranging alternative contraception if you need protection against pregnancy.

Contraception is free on the NHS through GP surgeries, sexual health clinics and some pharmacies. Fitting and removing implants and coils, and injections, are provided by trained clinicians in these settings.

Private clinics and online prescribers also offer contraception, with costs. Whichever route you use, it helps to tell your GP what method you are using so that your medical record is complete.