There is no conclusive evidence that using intrauterine devices (IUDs) causes weight gain. In some studies, hormonal IUD users experienced slight weight gain after having the device inserted, but it was not linked to the IUD. Copper IUDs, which do not contain any hormones, are not associated with weight gain.
What Are IUDs?
An IUD is a small device placed in the uterus to prevent pregnancy. They can be kept in place for up to three to 10 years depending on which brand of IUD you use. IUDs are more than 99% effective at preventing pregnancy, making them one of the most reliable forms of contraception.
IUDs prevent pregnancy in one of two ways:
- Hormonal IUDs: Hormonal IUDs include a progestin called levonorgestrel, which is used in many types of birth control pills. This progestin essentially makes every step of conception (ovulation, fertilization, and implantation) much more unlikely so the chances of becoming pregnant are very low. The device’s T-shape also helps block sperm from reaching the egg.
- Copper IUDs: Nonhormonal IUDs use copper instead of progestin to prevent pregnancy. The device is wrapped in a very thin copper wire that emits copper ions. These ions are toxic to sperm, causing them to die before they can reach the egg. These devices also feature the T-shape that creates an additional barrier against sperm.
IUDs and Weight Gain
Many people think weight gain is a side effect of using hormonal contraceptives. However, this belief seems to stem from anecdotal evidence rather than scientific studies.
In studies focusing specifically on hormonal birth control methods that contain only progestin (such as hormonal IUDs), the findings include:
- An average weight gain of less than 2 kilograms (4.4 pounds) for women using progestin-only birth control over a 12-month period. However, participants using other birth control methods gained about the same amount of weight over the same period.
- Women with progestin-only IUDs experienced greater increases in body fat and decreases in lean mass compared to women using nonhormonal IUDs for birth control.
Copper IUDs do not contain hormones, which are often thought to be the trigger for birth-control-related weight gain. There has been no evidence of significant weight change in women with copper IUDs.
Despite a lack of sufficient scientific proof, the rumors about hormonal birth control and weight gain seem to persist. While women might gain weight after getting an IUD or another form of birth control, it doesn’t mean the IUD is to blame.
There are many reasons some women might report that birth control caused them to gain weight, including:
- Fluid retention: Bloating is sometimes a side effect of hormonal birth control.
- Age: Most people tend to gain weight over time.
- Lifestyle: Any changes to exercise, diet, or daily routine while on birth control could be contributing factors to weight gain.
Known IUD Side Effects
IUDs do have side effects you should be aware of before choosing this form of birth control.
One of the most common side effects of using an IUD is a change in your period. Hormonal IUDs can cause periods to become lighter or less frequent, with some spotting as your body adjusts to the device. Spotting or irregular bleeding is most likely to occur during the early months of use and should improve over time.
Some women who have hormonal IUDs stop getting their periods. This is most likely to occur with Mirena, which has higher levels of levonorgestrel and is FDA-approved for treating heavy menstrual bleeding.
Less common symptoms that may occur with hormonal IUDs include:
- Breast tenderness
- Ovarian cysts
Copper IUDs might lead to heavier and longer periods as well as spotting between periods. This is most likely to occur during the first months of use. The only other symptom commonly associated with the copper IUD is having more intense and/or more frequent menstrual cramps.
Two less common side effects of both nonhormonal and hormonal IUDs are the risk of developing a pelvic infection after having an IUD inserted and the risk of the IUD being expelled from the body, in which case a medical provider will need to reinsert or replace it.
What Are the Benefits of IUDs?
IUDs come with significant benefits, especially when compared to other contraceptives. These benefits include:
- Efficacy: With a 99% effectiveness rate, IUDs are one of the most reliable forms of birth control.
- Extended protection: Hormonal IUDs can be used for three to five years depending on the brand. The copper IUD lasts for up to 10 years.
- Return to fertility: The IUD is a reversible form of birth control. Once you have it removed, your fertility will go back to its natural level right away.
- Easy to use: Once the IUD is in, you don’t have to do anything else to stay protected until it needs to be replaced.
- Inexpensive: Compared to other forms of birth control, IUDs are very cost-effective.
- Discreet: An IUD is completely private because no one can tell you’re using it, including your sexual partners.
How to Get An IUD
You can’t put an IUD in yourself. You must have a local medical provider insert and remove this type of contraception. At your appointment, the healthcare provider will pass the device through your vagina and your cervix to place it in the uterus. There will likely be some discomfort as the IUD is being inserted, but once it’s in place you won’t be able to feel it. You might experience some cramping, pain, dizziness, or irregular bleeding shortly after insertion.
Each IUD has strings that hang down from the bottom of the T shape. Your medical provider will cut the strings to the appropriate length so they sit at the back of your vagina. Your provider can also show you how to find the strings so you can check to make sure your IUD is in place.
Hormonal IUDs take up to seven days to start working, so you might need to use backup protection (such as condoms) for a week after having one inserted. Copper IUDs, on the other hand, begin working immediately and can also be used as emergency contraception.
While IUDs might not cause weight gain, you should still consider all your options before choosing this form of contraception.