Some IUDs are hormonal and some are not. There are currently four hormonal IUDs available in the United States (Mirena, Liletta, Kyleena, and Skyla) and one non-hormonal option (Paragard), which uses copper instead. The distinction matters because each type prevents pregnancy differently, lasts a different length of time, and affects your body in different ways.
Hormonal vs. Non-Hormonal IUDs
All four hormonal IUDs contain the same synthetic progestin, called levonorgestrel, but in different amounts and with different lifespans. Here’s how they break down:
- Mirena: Contains 52 mg of levonorgestrel. Approved for up to 8 years.
- Liletta: Contains 52 mg of levonorgestrel. Approved for 6 to 8 years.
- Kyleena: Contains 19.5 mg of levonorgestrel. Approved for up to 5 years.
- Skyla: Contains 13.5 mg of levonorgestrel. Approved for up to 3 years.
The non-hormonal option, Paragard, is wrapped in copper wire instead. It releases copper ions into the uterus and contains zero hormones. Paragard is approved for up to 10 years.
How Each Type Prevents Pregnancy
Hormonal IUDs work primarily inside the uterus. The levonorgestrel they release thickens the cervical mucus so sperm can’t pass through, interferes with sperm’s ability to function, and thins the uterine lining. These effects are largely local, meaning the hormone concentrates in the uterus rather than flooding the entire bloodstream the way a birth control pill does. Mirena, for example, starts by releasing about 21 micrograms of hormone per day, then gradually tapers to about 7 micrograms per day by year eight.
The copper IUD takes a completely different approach. Copper is toxic to sperm. Once Paragard is in place, the copper ions it releases impair sperm movement and function, preventing them from ever reaching an egg. No hormones are involved at any point.
How Effective They Are
Both types of IUD are over 99% effective at preventing pregnancy, and there’s virtually no gap between “typical use” and “perfect use.” That’s because once an IUD is inserted, there’s nothing you need to remember to do. You can’t take it incorrectly or forget a dose. This makes IUDs one of the most reliable forms of birth control available.
How Hormonal IUDs Affect Your Period
This is one of the biggest practical differences between the two types. Hormonal IUDs tend to make periods lighter over time, and many users eventually stop getting a period altogether. The higher the hormone dose, the more likely this is. After one year of use, about 20% of Mirena users have no periods at all, compared to 12% of Kyleena users and 6% of Skyla users.
For people with heavy menstrual bleeding, this effect can be life-changing. In clinical studies, people using a levonorgestrel IUD saw their menstrual blood loss drop by about 93% within three cycles and nearly 98% by six cycles. Mirena is actually FDA-approved as a treatment for heavy periods, not just as contraception.
The copper IUD, on the other hand, often has the opposite effect. Many Paragard users experience heavier, longer, or crampier periods, especially in the first few months.
How Much Hormone Actually Enters Your Body
A common concern with hormonal IUDs is whether they cause the same systemic side effects as the pill, the patch, or the hormonal ring. The answer is: generally far less. Hormonal IUDs act mainly within the uterus itself, with the FDA describing their effects as “mainly local progestogenic effects in the uterine cavity.” The daily hormone dose is measured in micrograms, not milligrams, and it decreases steadily over the device’s lifespan.
That said, some levonorgestrel does reach the bloodstream, and some users do report mood changes, acne, breast tenderness, or other hormonal effects. These tend to be milder and less common than with oral contraceptives, but they aren’t zero. If you’re specifically trying to avoid any hormonal exposure, the copper IUD is the only IUD option that guarantees that.
Choosing Between the Two Types
The decision often comes down to how you feel about hormones and how you feel about your period. If lighter periods (or no period) sounds appealing, or if you already deal with heavy bleeding, a hormonal IUD is worth considering. Mirena and Liletta deliver the highest dose and have the strongest effect on bleeding. Kyleena and Skyla use less hormone and are physically smaller, which can make insertion easier for people who haven’t been pregnant.
If you want to avoid hormones entirely, prefer to keep a natural menstrual cycle, or need emergency contraception (Paragard can work as emergency contraception if inserted within five days of unprotected sex), the copper IUD is your option. The trade-off is potentially heavier periods, particularly in the first several months.
Both types are reversible. Fertility typically returns quickly after removal regardless of which type you use or how long it’s been in place.