The contraceptive implant is a small, flexible rod placed under the skin of the upper arm that steadily releases progestogen to prevent pregnancy. It's more than 99% effective, lasts up to about 3 years, and — like the IUD — needs nothing to remember day to day. The most common side effect is a change in bleeding pattern.
How it works
According to the NHS and ACOG, the implant releases a steady low dose of progestogen, which:
- Stops ovulation (no egg is released),
- Thickens cervical mucus so sperm can't get through, and
- Thins the lining of the uterus.
It's a long-acting reversible contraceptive (LARC) — the same category as the IUD — meaning it works for years with no daily effort.
How effective is it?
The implant is over 99% effective. Because there's no daily pill to miss or per-act step, its real-world (typical-use) effectiveness matches perfect use — one of the reasons LARCs outperform the pill day to day. See the full methods comparison.
Insertion and removal
- Insertion: a provider numbs a small area of the upper arm and inserts the rod just under the skin — usually a few minutes. You may have bruising or tenderness for a few days.
- It works in the background for up to ~3 years.
- Removal: a provider removes it through a tiny incision; it can come out any time you choose.
Side effects
The most common change is to your bleeding pattern:
- Periods may become irregular, lighter, or stop altogether.
- Some people have more frequent or prolonged bleeding, especially in the first months.
Other possible effects include headaches, acne, breast tenderness, and mood changes — often settling within a few months. The implant is progestogen-only, so it avoids estrogen-related risks, making it suitable for many people who can't take the combined pill.
Like most methods, the implant is not reliably linked to weight gain for most people — see does birth control cause weight gain.
What it doesn't do
The implant prevents pregnancy only — it offers no STI protection. Use condoms to reduce STI risk.
The bottom line
The implant is a "fit and forget" option: highly effective, long-lasting, estrogen-free, and quickly reversible. The main trade-off is unpredictable bleeding, particularly early on. If a low-maintenance, top-tier-effective method appeals, it's worth discussing with a provider.
