How do hormonal IUDs and copper IUDs differ?

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Blister pack of 28 oral contraceptive pills arranged in four rows, with 21 white active pills followed by 7 orange inactive pills. Arrows indicate the order for taking pills. — birth control A 28-day package of birth control pills.

Hormonal and copper intrauterine devices (IUDs) are both highly effective, long-acting, reversible forms of birth control, but they function through different mechanisms and have distinct effects on the body.1

Mechanism of Action

Hormonal IUDs: These devices continuously release the synthetic hormone progestin, which thickens cervical mucus to block sperm and thins the uterine lining. Some versions also suppress ovulation.1
Copper IUDs: These release copper ions into the uterus, which impair sperm viability and prevent fertilization.1

Key Differences

Menstrual Impact: Hormonal IUDs often lead to lighter, less painful periods and are sometimes used to manage conditions like endometriosis. Conversely, copper IUDs may cause heavier, longer periods and increased cramping.1
Duration: Depending on the specific product, hormonal IUDs provide protection for three to eight years, while some copper IUDs can last up to 10 years.1
Onset: Copper IUDs provide protection immediately upon insertion, whereas hormonal IUDs typically require about a week to become effective unless inserted during menstruation.1