The birth control implant (sold as Nexplanon) causes side effects in roughly two-thirds of users, though most are mild and tend to improve within the first few months. The most common issue by far is a change in your bleeding pattern, particularly irregular spotting. Beyond that, a smaller percentage of users experience mood changes, headaches, nausea, weight gain, or acne.
Bleeding Pattern Changes
Irregular bleeding is the side effect you’re most likely to notice, and it’s often the reason people consider having the implant removed. In FDA clinical trial data, about 5.6% of users reported spotting between periods and 5.4% reported heavier menstrual bleeding. But those numbers understate how common some kind of bleeding change is. Spotting is especially frequent in the first 6 to 12 months as your body adjusts to the steady release of a progestin hormone.
Some people find their periods become lighter or stop altogether, which is not harmful. Others experience longer, heavier, or less predictable periods. There’s no reliable way to predict which pattern you’ll get before trying the implant. If bleeding changes bother you after a few months, a healthcare provider can discuss options, which sometimes include a short course of supplemental medication to manage it.
Mood Changes and Depression
Depression was reported by 3.4% of users in clinical trials, and anxiety by 3.2%. These numbers are relatively small, but mood-related side effects tend to be the ones people find most disruptive.
A large Danish study looking at all hormonal contraceptives found that users had a modestly higher likelihood of starting an antidepressant compared to nonusers. Progestin-only methods (the category the implant falls into) carried a relative risk of about 1.34 for beginning antidepressant use. Teenagers ages 15 to 19 appeared more sensitive to this effect, with progestin-only methods carrying a relative risk of 2.2 for a first antidepressant prescription in that age group. That doesn’t mean the implant causes depression in most users, but it does suggest that some people, particularly younger users, are more vulnerable to hormonal mood shifts.
If you have a history of depression or notice persistent low mood, irritability, or emotional flatness after insertion, that’s worth bringing up with your provider rather than waiting it out.
Weight Gain
Weight gain is one of the most-searched concerns about the implant, and the data shows it does happen, though the amount varies. A study tracking adolescent and young adult women found that normal-weight users gained an average of about 1.4 kg (roughly 3 pounds) in the period after insertion. Users who were overweight at baseline gained closer to 3 kg (about 6.5 pounds), and those who started in the obese category gained an average of about 3.7 kg (around 8 pounds).
Among those who had the implant removed specifically because of weight concerns, 65.5% had gained 5% or more of their body weight, compared to about 34 to 39% of people who kept the implant or removed it for other reasons. So while not everyone gains a noticeable amount, people who are already at a higher weight may be more likely to experience meaningful changes.
Other Common Side Effects
Several other side effects appeared in more than 2% of clinical trial participants:
- Nausea: reported by 3.6% of users, typically mild and most common in the first few weeks
- Headaches: reported by 2% of users
- Acne: reported by 2.4%, which can mean new breakouts or a worsening of existing acne
- Fatigue: reported by 2.2%
- Painful periods: reported by 2.6%, sometimes alongside heavier bleeding
These side effects overlap with symptoms many people experience for other reasons, which can make it hard to tell whether the implant is the cause. Tracking your symptoms before and after insertion gives you a clearer picture.
What to Expect at the Insertion Site
The implant is a small, flexible rod placed just under the skin of your upper arm. Mild discomfort and bruising around the insertion site are normal and typically resolve within a week or two. Simple painkillers or an ice pack help with soreness in the first few days. A small bandage covers the site, and you can usually return to normal activities right away.
Signs of a problem at the site include increasing redness, swelling, persistent itching, or oozing fluid. These could indicate an infection and need medical attention.
Rare but Serious Complications
Implant migration is the most widely reported serious complication, though it remains very rare. The UK’s medicines regulator documented 126 reports of implant migration through June 2019. Worldwide, 107 cases of migration to the pulmonary artery or chest were identified over a roughly 21-year period since the implant first launched. Given the millions of implants placed during that time, the individual risk is extremely low.
Migration is more likely when the implant is inserted too deeply, placed in the wrong location, or inserted in a very thin arm. Updated guidelines now specify a particular insertion site on the inner upper arm to reduce this risk. If you can’t feel the implant under your skin at any point, contact your provider, because a “lost” implant may not be providing contraception and may need imaging to locate.
How Long Side Effects Last
Most negative side effects improve within the first few months as your body adapts to the hormone. Spotting and irregular bleeding are most pronounced in the first 6 to 12 months and often settle into a more predictable pattern after that, though for some users they persist for the life of the implant. Mood-related effects, nausea, and headaches typically resolve sooner, often within the first three months.
If side effects are still bothering you after a few months, that’s a reasonable point to reassess whether the implant is the right fit. It can be removed at any time, not just at the end of its lifespan.
Fertility After Removal
The implant does not cause any lasting effect on fertility. It’s possible to get pregnant right away after removal, because the hormone clears your system quickly once the rod is out. Ovulation can resume within days to weeks. If you’re having the implant removed and don’t want to become pregnant, you’ll need another form of contraception immediately.
The implant itself is over 99% effective while in place, meaning fewer than 1 out of 100 users will become pregnant per year. That makes it one of the most reliable reversible contraceptive methods available, which for many people offsets the adjustment period of side effects.