The birth control that goes in your arm is called Nexplanon, a small flexible rod about the size of a matchstick that sits just under the skin of your upper arm and releases a steady dose of a synthetic hormone to prevent pregnancy. It’s one of the most effective contraceptive methods available, with a real-world failure rate of roughly 0.02 pregnancies per 100 women per year. The FDA recently extended its approved duration from three years to five.
How the Implant Prevents Pregnancy
The rod contains 68 mg of a synthetic progestin that slowly releases into your bloodstream over several years. It works through three mechanisms at once: it stops your ovaries from releasing eggs, thickens the mucus at the opening of your cervix so sperm can’t easily pass through, and changes the lining of your uterus in ways that make pregnancy less likely. Because all three of these effects happen continuously without you needing to do anything, the implant is considered a “set it and forget it” method.
How Effective It Is
The implant is more effective than the pill, the patch, the ring, and even most IUDs. In a large real-world study (the NORA study), the Pearl Index for Nexplanon was 0.02, meaning roughly 2 pregnancies per 10,000 women per year of use. Under perfect conditions, previous studies have found failure rates between zero and 0.06. The reason it performs so well in everyday life is that there’s no room for human error. You can’t forget to take it, use it incorrectly, or skip a dose.
What Getting It Feels Like
A nurse or doctor fits the implant in a quick office visit that takes only a few minutes. They’ll numb a spot on the inner side of your non-dominant upper arm with a local anesthetic, then use a special applicator to slide the rod just beneath the skin. You won’t see it once it’s in place, but you can feel it if you press on the area. The site gets covered with a small dressing, which you can remove once the cut heals.
Most people describe the experience as painless during the procedure itself, with some soreness or bruising around the insertion site for a few days afterward. Your provider will ask you to feel the rod under your skin before you leave, so you know how to check that it’s still in place.
How Long It Lasts
The FDA approved Nexplanon for up to five years of continuous use in 2024, an extension from its original three-year approval. That decision came after a clinical trial of 399 women who continued using the implant into years four and five. No pregnancies occurred during that extended period, and no new safety concerns emerged. Once your five years are up, a provider can remove the old implant and insert a new one in the same appointment if you’d like to continue.
Changes to Your Period
The most common side effect is a shift in your bleeding pattern, and this is the main reason some people choose to have the implant removed early. About 23% of users experience frequent or prolonged spotting. Others find their periods become lighter or stop altogether. Some have unpredictable bleeding that doesn’t follow any regular cycle.
One important thing to know: whatever bleeding pattern you settle into during the first three months is likely the pattern you’ll have for the duration of use. It’s generally not something that improves with more time, unlike some IUDs where irregular bleeding tends to taper off over the first six months to a year.
Weight Gain and Other Side Effects
Weight gain is one of the most common concerns people have about the implant. A randomized controlled trial comparing implant users to a control group found that perceived weight gain was much more common among implant users (15.3% reported it at three months versus 4.3% in the control group). But when researchers actually measured everyone’s weight, the two groups didn’t differ significantly. At three months, implant users had gained a median of 0.5 kg (about a pound), while the control group gained 0.0 kg. The risk of gaining more than about 4.5 pounds was the same in both groups.
That doesn’t mean no one gains weight on the implant, but the data suggests the hormone itself isn’t a major driver of weight change for most people. Other side effects can include headaches, breast tenderness, and mood changes, though these vary widely from person to person.
Removal and Fertility Return
You can have the implant taken out whenever you want. Removal follows the same basic process as insertion: a local anesthetic, a small cut in the skin, and the rod is pulled out. The whole thing takes a few minutes. It’s possible to get pregnant right away after removal. Unlike some hormonal methods that can delay your return to fertility for weeks or months, the implant stops releasing hormone the moment it’s out, and ovulation can resume quickly.
Rare Risks to Know About
In rare cases, the implant can migrate from the insertion site. Up to June 2019, the UK’s medicines regulator had received 126 reports of implant migration, with 18 of those involving the lung. Worldwide, 107 cases of migration to the pulmonary artery or lung were identified over a roughly 20-year period since the product launched. This is extremely uncommon given the millions of implants placed during that time, but it’s the reason providers are trained to insert the rod at a very specific location and depth, and why you should periodically feel your arm to confirm the implant is still where it should be. If you can no longer feel it, or if you develop unusual bruising at the insertion site or shortness of breath, that warrants a prompt visit to your provider.
Cost and Access
In the United States, the implant can cost anywhere from $0 to $2,300, depending on your insurance. Most health insurance plans cover it entirely under the Affordable Care Act’s contraceptive coverage mandate. Government programs like Medicaid and Title X clinics (including Planned Parenthood) also provide it at low or no cost for people who qualify. Removal typically costs between $0 and $300. When you factor in the five-year lifespan, even the higher out-of-pocket price works out to less per month than many other methods.