How does an IUD work?

An IUD is a small device inserted into the uterus to prevent pregnancy. It has a string for removal and is over 99% effective, long-term, and reversible.

There are two types: hormonal IUDs, which use levonorgestrel to thicken cervical mucus and thin the uterine lining, and copper IUDs, which alter sperm movement to prevent them from reaching an egg.

The doctor inserts the IUD through the cervix into the uterus using a speculum and a special inserter. The process usually takes less than five minutes, and some people may experience dizziness or faint.

After insertion, cramping and spotting are common but typically resolve within three to six months. Hormonal IUDs can lighten periods, while copper IUDs may make them heavier and worsen cramps. IUDs can be removed quickly if pregnancy is desired.

If inserted during the first four days of a period, IUDs are immediately effective. Otherwise, protection begins after seven days. IUDs can also be used as emergency contraception, being over 99% effective if inserted within five days of unprotected sex.

IUDs do not cause weight gain, do not change sex drive, and do not protect against sexually transmitted diseases.