Can Hormonal IUDs Cause Weight Gain?
Hormonal IUDs like Mirena (levonorgestrel-releasing IUS) are associated with modest weight gain of approximately 1-3 kg over the first year, though this increase is not consistently different from copper IUD users and may not be clinically significant for most patients. 1, 2
Evidence on Weight Changes with Hormonal IUDs
Comparative Weight Gain Data
The most rigorous comparative data shows variable results:
In the largest adjusted analysis (Contraceptive CHOICE Project, n=427), levonorgestrel IUD users gained a mean of 1.0 kg over 12 months, which was not statistically different from copper IUD users (0.2 kg) after adjusting for confounders. 2 This study found that only Black race—not contraceptive method—was a significant predictor of weight gain (1.3 kg).
A smaller prospective study found LNG-IUS users gained 2.9 kg at 12 months compared to 1.4 kg in copper IUD users, but this difference was not statistically significant between groups. 3 Importantly, LNG-IUS users showed a 2.5% gain in fat mass (p=.0009) and 1.4% loss of lean mass, suggesting body composition changes may occur even when total weight change is modest. 3
Body Composition Changes Matter More Than Weight Alone
The key concern is not just weight but body composition—LNG-IUS users tend to gain fat mass while losing lean mass, whereas copper IUD users show the opposite pattern. 3
- LNG-IUS users experienced increased fat mass (+2.5%) and decreased lean mass (-1.4%) at 12 months. 3
- Copper IUD users showed decreased fat mass (-1.3%) and increased lean mass (+1.0%), possibly related to higher rates of physical activity in this group. 3
- The central-to-peripheral fat ratio did not differ significantly between groups, suggesting no preferential central fat accumulation with hormonal IUDs. 3
Clinical Context and Counseling
Baseline Weight Documentation
The CDC explicitly recommends measuring baseline weight and BMI not because clinically significant weight gain is expected, but to facilitate counseling for women who perceive weight changes with their contraceptive method. 4, 1
- Weight measurement is not required for medical eligibility—all IUD types can be used regardless of BMI. 4, 1
- Baseline documentation allows objective comparison if patients express concerns later. 1, 5
Comparison to Other Contraceptive Methods
When counseling weight-conscious patients, context matters:
Depot medroxyprogesterone acetate (DMPA) causes the greatest weight gain among contraceptive methods and should be avoided when weight is a primary concern. 5 DMPA users gained 2.2 kg at 12 months 2, with one study showing 1.9 kg gain resulting primarily from increased fat mass (+1.6 kg). 6
Copper IUDs remain the most weight-neutral contraceptive option, with no hormonal exposure. 5 However, even copper IUD users in reproductive years tend to gain weight over time (2.8 kg over 5 years, 3.9 kg over 7 years) due to age-related factors independent of contraception. 7
Management Approach
When Patients Report Weight Gain
If a patient using a hormonal IUD reports weight gain:
- Document current weight and calculate BMI to compare against baseline. 5
- Investigate alternative causes: dietary changes, reduced physical activity, medical conditions (thyroid dysfunction, PCOS), and other medications. 5
- Counsel that device removal is available at any time if side effects are unacceptable. 1
Preventive Counseling at Insertion
Set realistic expectations: modest weight changes (1-3 kg) may occur but are highly variable between individuals, and body composition changes may be more relevant than total weight. 2, 3
- Emphasize that highly effective contraception should not be withheld due to weight concerns alone, as contraceptive benefits typically outweigh modest weight changes. 1
- For patients where weight is the primary concern, consider copper IUD as the most weight-neutral option. 5
Important Caveats
- Weight change is highly variable—the range spans from weight loss to significant gain across all contraceptive methods, making individual prediction impossible. 2
- Age is a significant factor: older women gain more weight during reproductive years regardless of contraceptive method. 7
- Physical activity levels may influence body composition changes more than the contraceptive method itself. 6, 3