Nexplanon is over 99% effective, making it one of the most reliable birth control methods available. But in rare cases, the implant can fail or be compromised. The most definitive sign that Nexplanon isn’t working is a positive pregnancy test. Beyond that, there are specific physical checks and risk factors that can help you gauge whether your implant is doing its job.
Check That You Can Feel the Implant
The single most important thing you can do is press gently along the inside of your upper arm where the implant was placed. You should be able to feel a small, thin rod just under the skin, roughly the size of a matchstick. If you can feel it, it’s almost certainly in the right position and releasing hormone as intended.
If you can’t feel the implant at all, that’s a reason to act. In some cases, the device was never properly delivered during insertion. This is documented but uncommon. In other cases, the implant was placed too deep, which happens in roughly 1 out of every 1,000 insertions. A deeply placed implant may still release hormone, but there’s no way to confirm that without medical help. Your provider can locate it using a high-frequency ultrasound or, because Nexplanon is radiopaque, a standard X-ray. Until the implant is found and confirmed to be in place, you should use a backup method of birth control.
Migration more than 2 centimeters from the original insertion site is rare, but it does happen. If you notice the rod seems to have shifted significantly, or if the area around it looks or feels different than it used to, that’s worth getting checked.
Medications That Can Reduce Effectiveness
Nexplanon works by releasing a steady dose of a progestin hormone that suppresses ovulation, thickens cervical mucus, and changes the uterine lining. Certain medications speed up how your liver processes that hormone, which can lower the amount circulating in your body enough to undermine its contraceptive effect. This is one of the more common and underappreciated reasons the implant might not work as expected.
The medications that can interfere with Nexplanon include:
- Seizure medications: carbamazepine, oxcarbazepine, phenytoin, felbamate, topiramate
- Barbiturates
- Antibiotics and antifungals: rifampin, griseofulvin
- HIV medications
- Hepatitis C medications
- Other: bosentan (for pulmonary hypertension), aprepitant (for nausea)
- Supplements: St. John’s wort
St. John’s wort catches many people off guard because it’s sold as an herbal supplement, not a prescription drug. If you’ve been taking any of these while relying on Nexplanon alone, your protection may be reduced. Using condoms as a backup is a practical step while you sort out alternatives with your provider.
Pregnancy Symptoms vs. Normal Side Effects
This is where things get tricky. Nexplanon’s known side effects overlap significantly with early pregnancy symptoms. Irregular bleeding, spotting, cramping, breast tenderness, nausea, and abdominal pain are all reported side effects of the implant itself. So experiencing any of these doesn’t necessarily mean the implant has failed.
What should raise your suspicion is a change from your established pattern. If you’ve had the implant for months and your body has settled into a rhythm, whether that’s light periods, no periods, or occasional spotting, a sudden shift is worth paying attention to. In one documented case of implant failure, a woman returned to her clinic 17 months after insertion reporting irregular spotting and cramping that felt different from her usual experience. A home pregnancy test confirmed the pregnancy.
A home pregnancy test is cheap, fast, and the most direct way to answer the question. If you’re experiencing symptoms that feel off, take one. Modern urine tests are accurate enough to detect pregnancy about two weeks after conception. If the result is positive, contact your provider promptly. One important detail: when pregnancy does occur with an implant in place, there is an increased risk of ectopic pregnancy, where the embryo implants outside the uterus. This requires medical attention, so don’t delay.
How Long the Implant Lasts
Nexplanon was originally approved for three years of use. In 2024, the FDA extended that to five years based on a clinical trial of 399 women who continued using their implants beyond the three-year mark. During years four and five, zero pregnancies were recorded, producing a failure rate of 0.0 per 100 women-years. No new safety concerns emerged either.
So if your implant is approaching the three-year mark and you were told it needs replacement, you now have more time. That said, the five-year window is the ceiling. If your implant is past five years, its hormone output may no longer be sufficient to prevent pregnancy, and you should plan for replacement or switch to another method.
When Failure Actually Happens
With perfect use and typical use both showing a 0.1% failure rate, Nexplanon is the most effective reversible contraceptive on the market. For context, that means roughly 1 in 1,000 women using the implant for a year will become pregnant. The majority of documented failures trace back to one of three causes: the implant wasn’t properly inserted in the first place, a medication interaction lowered hormone levels, or the implant was past its effective lifespan.
True “spontaneous” failure, where the implant is correctly placed, nothing interferes with it, and pregnancy occurs anyway, is extraordinarily rare. If you can feel the rod in your arm, you aren’t taking any interacting medications, and you’re within the five-year window, the implant is almost certainly working. If any of those three conditions isn’t met, a pregnancy test and a visit to your provider are reasonable next steps.