Does an IUD or Nexplanon Cause Weight Gain? Device-by-Device Evidence Review

For most women, an IUD or the Nexplanon implant causes little or no weight gain beyond what the years would have added anyway. In long-term studies, women using a hormonal IUD such as Mirena gained about as much as women using the hormone-free copper IUD (Paragard)^[1][2]. The implant has a small but real signal in some studies: roughly 2 kg more than copper-IUD users over three years in a large WHO trial^[3], though other studies found no difference once they adjusted for other factors^[2]. The one method with consistent weight-gain evidence is the Depo-Provera shot^[4][5]. And the comparison group that matters most, women on the copper IUD with no hormones at all, gained weight too, because adult women tend to gain as the years pass^[1].

The short answer, device by device

• Hormonal IUD (Mirena, Liletta, Kyleena, Skyla): tracks the copper IUD. Over up to ten years of use, hormonal IUD users gained 4.0 kg and copper IUD users 4.9 kg, a difference that was not statistically significant^[1].
• Nexplanon implant: a small, inconsistent signal. The FDA label reports a mean gain of 3.7 lb after two years and says how much of it the implant caused “is unknown”^[6]. Against copper IUD users, the extra gain ranges from none to about 2 kg over three years^[2][3].
• Copper IUD (Paragard): no hormones, no weight warning. Weight gain does not appear among the adverse reactions on its label^[7]. Users still gain slowly with age.
• Depo-Provera: the outlier. Its label reports an average gain of 16.5 lb after six years^[5], and it produced more gain than the IUDs and implant it was compared with in two large studies^[1][8].

Why the copper IUD is the comparison that matters

Many women gain weight through their 20s, 30s and 40s whether or not they use birth control, so comparing your weight before and after a device tells you little on its own. The copper IUD solves that problem. It prevents pregnancy without any hormones^[7], so women using it show the background drift that happens anyway. In the studies below, copper IUD users gained 0.2 kg over 12 months^[2], 1.1 kg over three years^[3], 1.5 kg over 12 to 18 months in a large African trial^[8] and 4.9 kg over ten years^[1]. The useful question is not “Did I gain weight on my IUD?” but “Did I gain more than I would have on a hormone-free method?”

The Cochrane review of progestin-only contraceptives, the most thorough synthesis on this question, pooled 22 studies with 11,450 women^[9]. It rated the overall evidence as low quality, mostly because few studies were randomized and many women dropped out. Its conclusions still hold up: mean gain at 6 or 12 months was under 2 kg (4.4 lb) in most studies, gain at two to four years was roughly double the one-year figure, and “generally the study groups did not differ significantly.” The authors added that honest counseling about typical weight gain could keep women from abandoning a method because they think it made them gain.

Does Nexplanon cause weight gain?

The Nexplanon label is unusually direct about weight. It has a dedicated “Weight Gain” section in its warnings, lists weight increase among its most common adverse reactions (13.7% of 942 women in three-year trials) and reports that 2.3% of users had the implant removed because of weight gain^[6]. The same label also lists both “increased appetite” and “weight decreased” among reactions reported after approval.

“In clinical studies, mean weight gain in U.S. non-radiopaque etonogestrel implant (IMPLANON) users was 2.8 pounds after one year and 3.7 pounds after two years. How much of the weight gain was related to the non-radiopaque etonogestrel implant is unknown.”

— NEXPLANON prescribing information, §5.9 Weight Gain

Those label numbers come from trials without a hormone-free comparison group. The comparative studies point in slightly different directions:

• No significant difference after adjustment. In the U.S. CHOICE cohort, implant users gained 2.1 kg over 12 months versus 0.2 kg for copper IUD users, but the difference disappeared once researchers adjusted for other factors^[2]. A second CHOICE analysis that measured body fat and lean mass found no difference in weight or body composition between implant, hormonal IUD and copper IUD users over 12 months, although it included only 33 implant users^[10].
• A small difference over three years. In a WHO trial across seven countries, about 1,000 women randomized to the etonogestrel implant (Nexplanon’s hormone) gained 3.0 kg at 36 months, versus 1.1 kg for about 970 age-matched copper IUD users. The authors called this a small increase “with little clinical significance”^[3].
• A similar signal for a different implant. In the randomized ECHO trial of 7,829 women, users of a levonorgestrel implant (not Nexplanon, but the same class of device) gained 0.87 kg more than copper IUD users over 12 to 18 months^[8].
• More reported gain than the hormonal IUD. A meta-analysis of six randomized trials comparing implants head-to-head with the levonorgestrel IUD found implant users were more likely to report weight gain (odds ratio 4.63)^[11]. This counted weight gain reported as a side effect rather than measured weight, and it pooled older implant designs with newer ones.

Timing adds useful context. A Colorado study of 1,024 adolescents and young adults compared weight in the 6 to 18 months before implant insertion with the 6 to 18 months after^[12]. Patients were already gaining before the implant, and it did not speed that up in any weight category. But the 84 patients who had the implant removed for weight concerns had gained more after insertion, and 65.5% of them gained at least 5% of their body weight. The honest reading: on average, Nexplanon adds little, but a subset of women do gain more on it, and there is currently no reliable way to know in advance who they will be.

Does a hormonal IUD (Mirena, Liletta, Kyleena, Skyla) cause weight gain?

Hormonal IUDs release the progestin levonorgestrel inside the uterus. Mirena’s label puts the release rate at about 21 mcg a day shortly after insertion, falling to about 11 mcg a day after five years and 7 mcg after eight years^[13]. The long-term weight data are reassuring. In a Brazilian study that tracked 701 hormonal IUD users, 723 copper IUD users and 714 Depo-Provera users for up to ten years, hormonal IUD users gained 0.7 kg in the first year (copper: 0.2 kg) and 4.0 kg by year ten (copper: 4.9 kg), with no significant difference between the two IUDs^[1]. In the U.S. CHOICE cohort, hormonal IUD users gained 1.0 kg in a year versus 0.2 kg for copper, again not significant after adjustment^[2].

Mirena’s label does not list weight gain among the adverse reactions reported by at least 5% of 5,091 trial participants. In a separate extension study of 362 women using Mirena for six to eight years, 9% reported weight gain, and the label states that “it is unknown if the weight gain was caused by Mirena”^[13]. We found no dedicated weight studies of Liletta, Kyleena or Skyla in PubMed. They deliver the same hormone the same way, so the levonorgestrel IUD research above is the best available guide.

What about “Mirena belly”?

The closest study used body scans in Brazilian women matched by age and BMI^[14]. Over 12 months, hormonal IUD users gained 2.9 kg and copper IUD users 1.4 kg, a difference that was not significant. Hormonal IUD users did show a 2.5% gain in fat mass, but the ratio of trunk fat to limb fat changed no differently between the groups. The Cochrane review likewise notes two small studies in which body-fat percentage rose more in hormonal IUD users than in women using a non-hormonal method^[9]. So there is a small body-composition signal in small studies, but no evidence that a hormonal IUD redirects fat to the abdomen. What many women feel low in the belly may be something else: Mirena’s label lists abdominal or pelvic pain in 22.6% of trial users^[13], a real symptom in the same place, but not a change in fat.

Does the copper IUD (Paragard) cause weight gain?

Nothing in the evidence suggests it does. Paragard “does not contain any hormones,” and weight gain does not appear anywhere in its list of adverse reactions^[7]. The label does list abdominal distension (bloating) among reactions reported voluntarily after approval, and prolonged menstrual flow among reactions seen in trials. Copper IUD users do gain weight over time, as every study above shows, but that is the background drift of adult life, not the device.

How the devices compare with Depo-Provera

Depo-Provera is the benchmark because it is the method where the weight signal is consistent. Its label says plainly that “women tend to gain weight while on therapy”: from an average starting weight of 136 lb, women gained 5.4 lb after one year, 8.1 lb after two, 13.8 lb after four and 16.5 lb after six years. By 24 months, 37.7% had gained more than 10 lb, and 2% of trial participants withdrew because of excessive weight gain^[5]. A systematic review of 24 studies, none of them randomized, found that studies at moderate or high risk of bias suggest an association between the shot and weight gain and increased body fat mass^[4].

The randomized ECHO trial shows the gap most cleanly. Women assigned to Depo-Provera gained 3.5 kg over 12 to 18 months, versus 2.4 kg on a levonorgestrel implant and 1.5 kg on the copper IUD. The shot added 2.0 kg more than the copper IUD and 1.2 kg more than the implant^[8]. Over ten years, Depo-Provera users gained 6.6 kg, versus 4.0 kg on the hormonal IUD and 4.9 kg on the copper IUD^[1].

Why so many women feel they gained weight

The feeling is common and usually not imagined. Several things are happening at once:

• The years are doing some of the work. Copper IUD users gain too, and in the Colorado implant study patients were gaining at the same pace before insertion as after it^[12]. A device often gets the blame for a trend that started earlier.
• A perceived gain is usually a real gain, though not necessarily a device gain. In the CHOICE project, 34% of 4,133 new users perceived weight gain, and implant and Depo-Provera users were more likely to than copper IUD users. Women who perceived gain had gained a mean of 10.3 lb, and self-report matched the scale most of the time^[15]. If you think you’ve gained, you probably have. The open question is why.
• Expectation can create a perceived gain. In a Jamaican trial that gave women a levonorgestrel implant (not Nexplanon) either immediately or after a three-month delay, 15.3% of implant users perceived weight gain at three months versus 4.3% of women still waiting, yet measured weight did not differ between the groups^[16]. The authors warned that counseling women to expect weight gain may lead them to perceive it “even in its absence.”
• Bloating and fluid register as weight. Depo-Provera’s label lists bloating and swelling (edema) among its side effects, along with a fluid-retention precaution^[5], and Paragard’s lists abdominal distension^[7]. A bloated week changes the scale and the fit of your jeans without any change in body fat.
• Bleeding changes are the most common side effect, not weight. Changes in bleeding pattern top the adverse-reaction lists for both the implant^[6] and Mirena, where 18.4% of trial users stopped having periods^[13]. That adds no fat, but it can make it harder to tell ordinary cyclical puffiness from real change.

Using a GLP-1 medication with an IUD or implant

Tirzepatide (Zepbound, also sold as Mounjaro) slows stomach emptying and can make oral birth control pills less effective, so the Zepbound label advises pill users to switch to a non-oral method or add a barrier method for four weeks after starting and after each dose increase. The same label states that “hormonal contraceptives that are not administered orally should not be affected”^[17]. An IUD or implant doesn’t depend on absorption from your gut, so it needs no backup on account of the GLP-1. Reliable contraception matters here because the label also advises stopping Zepbound once pregnancy is recognized. For the details, see our explainers on the tirzepatide four-week backup-contraception warning, why semaglutide carries no pill warning and which contraceptive methods pair best with a GLP-1.

What to do with this

• If weight is one of your top concerns when choosing, the copper IUD and hormonal IUDs have the most reassuring long-term data, the implant has a small average effect with more individual variation, and Depo-Provera has the clearest signal. Weight is one factor among several (effectiveness, bleeding pattern, your medical history), and a clinician can help you weigh them.
• Measure rather than guess. Note your weight on the day of insertion and check it again at about 6 and 12 months on the same scale. If you have readings from the year before, those matter too: the implant study that separated the device from ordinary drift did it by comparing the trend before insertion with the trend after^[12].
• If you have gained substantially and it is bothering you, that is a legitimate reason to raise switching with your clinician. A minority of implant users do gain more than average^[12].
• If you are on Depo-Provera and your weight is climbing, bring it up early. It is the one method where the label and the randomized evidence agree that gain is expected^[5][8], and every long-acting device above showed less of it.