How it works
The implant is a small flexible rod placed under the skin on the inner side of the non-dominant upper arm. It releases a low dose of progestogen continuously, at a steady rate — without the peaks and troughs of a daily tablet. That progestogen blocks ovulation and thickens cervical mucus.
Its strength is that it takes the user out of the equation entirely: nothing to think about, nothing to renew, nothing to forget. That is why its real-world effectiveness is almost identical to its theoretical effectiveness, which is true of no method that depends on an action.
Insertion and removal
- Insertion: in a consultation, under local anaesthetic, in a few minutes. Soreness and bruising are common for a few days.
- Duration: three to five years depending on the product and on the authorisation in force in the country — this has changed recently in several places and is worth checking locally.
- Removal: possible at any time, on request, with no need to justify it. It is done under local anaesthetic through a small incision.
- Locating it: the implant must remain palpable. If it is not, imaging is needed before any removal.
Effectiveness
Under 0.1 pregnancies per 100 women per year, in perfect use and typical use alike. With the IUD it is the most effective reversible method available.
Bleeding: the thing to know before insertion
The implant almost always changes the pattern of periods, and does so unpredictably: some women have no periods at all, others have more frequent, longer or irregular bleeding (NHS, 2024), and many fall in between. This is neither dangerous nor a sign of a problem, but it is the leading reason for early removal. Being warned beforehand changes how it is experienced — and treatments exist to ease troublesome bleeding.
Precautions
- Interactions: enzyme inducers can reduce its effectiveness; tell the clinician fitting it.
- Contraindications: few — essentially hormone-dependent breast cancer, severe liver disease, or unexplained and uninvestigated genital bleeding.
- No oestrogen: the implant often remains usable where a combined pill is not, including with migraine with aura and while breastfeeding.
- No protection against sexually transmitted infections.
Return of fertility
Rapid: fertility returns as soon as the implant is removed (NHS, 2024). There is no recovery delay, unlike the injection.