Nexplanon, the small hormonal implant placed under the skin of your upper arm, is one of the most effective contraceptives available, with a real-world failure rate of just 0.02%. But like any hormonal method, it comes with side effects. The most common is irregular bleeding, especially during the first 6 to 12 months. Beyond that, you may experience headaches, acne, mood changes, or weight-related concerns. Most side effects ease within a few months as your body adjusts to the steady release of hormone from the implant.
Changes to Your Period
Irregular bleeding is the number one side effect and the most common reason people consider having the implant removed early. The pattern varies widely from person to person. Some users get lighter, less frequent periods. Others experience prolonged spotting that lasts weeks at a time. A smaller group stops getting periods altogether. There’s no reliable way to predict which pattern you’ll fall into before the implant is placed.
The first 6 to 12 months tend to be the most unpredictable. Spotting between periods, longer-than-usual bleeding episodes, and irregular cycle lengths are all typical during this window. For many users, bleeding patterns settle down after the first year, though they may never return to a perfectly regular schedule while the implant is in place. If your bleeding becomes heavy or disruptive after a few months, that’s worth bringing up with your provider, since there are short-term treatments that can help manage it.
Headaches, Acne, and Mood Changes
Headaches are among the most frequently reported mild side effects in clinical trials. They can appear in the first weeks after insertion and, for most people, become less frequent over time. If you’re prone to migraines, it’s worth tracking whether the implant changes their frequency or severity.
Acne is another common complaint. The hormone in Nexplanon is a type of progestin, and progestin-only methods lack the estrogen component found in combination pills that often helps keep skin clear. Some users develop new breakouts or notice existing acne worsening, particularly in the first few months.
Mood changes, including increased irritability, anxiety, or low mood, have been reported, though they were not among the most common side effects in clinical trials. Depression specifically was uncommon in study data. Still, hormones affect everyone differently. If you notice a persistent shift in your mood that feels out of character, that’s a meaningful signal worth paying attention to, not something to dismiss as “just hormonal.”
Weight Gain: Perception vs. Reality
Weight gain is one of the most frequently cited concerns about Nexplanon, but the clinical data tells an interesting story. In one study, 15.3% of implant users reported feeling like they had gained weight at the three-month mark, compared to just 4.3% in a control group not using the implant. However, when researchers actually weighed participants, the two groups showed no significant difference. Median weight gain at three months was just 0.5 kg (about one pound) for implant users versus 0.0 kg for controls.
This doesn’t mean your experience isn’t real if you feel heavier. Hormonal changes can affect water retention, appetite, and body composition in ways that the scale doesn’t always capture. But the evidence suggests that the implant itself doesn’t cause substantial weight gain for most users. Researchers have pointed out that simply warning people to expect weight gain may create a self-fulfilling perception, potentially contributing to early discontinuation of an otherwise highly effective method.
What Happens at the Insertion Site
The implant is placed just under the skin of your inner upper arm through a small insertion device. Bruising, tenderness, and mild swelling at the site are normal in the first week or two. Some people notice a small scar. Localized infection is possible but rare.
Over time, your body forms a thin layer of fibrous tissue around the implant, which is a normal response to any foreign object under the skin. In most cases this capsule is thin enough that you can still feel the implant through your skin. Occasionally, fibrosis can make the implant harder to locate by touch, which matters when it’s time for removal. Nexplanon is designed to be visible on X-ray specifically for this reason, making it easier to find if it can’t be felt.
Rare but Serious Risks
Implant migration is the most talked-about serious risk, and it’s genuinely rare. The estimated rate of implants found in blood vessels is approximately 1.3 per million implants sold worldwide. In these cases, the implant moves from its placement site into a blood vessel and can travel toward the lungs. Symptoms that have been associated with migration include difficulty breathing, unusual bruising or a blood-pooling bruise at the insertion site, or a combination of both. If you can no longer feel the implant where it was placed, that warrants prompt follow-up.
Pregnancy on Nexplanon is extremely uncommon. A large real-world study found a Pearl Index of 0.02 for pregnancies occurring while the implant was in place, meaning roughly 2 in 10,000 users per year. Among the small number of pregnancies that did occur in the study (including those just before insertion and just after removal), one was ectopic, a pregnancy outside the uterus. While the implant nearly eliminates pregnancy risk, if you do experience pregnancy symptoms, ectopic pregnancy needs to be ruled out quickly because it can become a medical emergency.
Medications That Can Reduce Effectiveness
Certain medications speed up the way your liver processes hormones, which can lower the amount of active hormone circulating from the implant. This potentially reduces its contraceptive effectiveness. The most well-known culprits include some anti-seizure medications (like carbamazepine, phenytoin, and topiramate), the antibiotic rifampicin (used for tuberculosis), and the herbal supplement St. John’s wort.
Some HIV and hepatitis C medications also interact with the implant’s hormone levels, either raising or lowering them depending on the specific drug. If you’re prescribed any of these, you’ll typically need to use a backup non-hormonal method (like condoms) while taking the medication and for 28 days after stopping it.
How Long Side Effects Typically Last
Most mild side effects peak in the first few months and then taper off as your body adapts. Planned Parenthood advises giving the implant at least a few months before deciding whether the side effects are tolerable long-term. Bleeding irregularities, the most disruptive side effect for many users, tend to be worst in the first 6 to 12 months before settling into a more predictable (if still different) pattern.
If side effects haven’t improved after several months, or if they’re significantly affecting your quality of life, removal is straightforward. The most common complication during removal is difficulty locating the implant, usually because it was placed too deeply. In those cases, imaging can pinpoint its position. The implant lasts up to three years, but you can have it taken out at any point before then.