How does the hormonal IUS work?

The hormonal IUS releases the hormone levonorgestrel in small amounts into the uterus.

IUS brand dosages:

  • Mirena® – 20 micrograms of levonorgestrel per 24 hours
  • Kyleena® – 17.5 micrograms levonorgestrel per 24 hours
  • Jaydess® – 13.5 micrograms of levonorgestrel per 24 hours
  • Levosert® – 20 micrograms of levonorgestrel per 24 hours

The dosage is therefore 20-100 times lower compared to taking the pill. With the pill, the hormone doses are higher because they first have to navigate the person’s metabolism or blood circulation before they become effective.

A hormonal IUS works effectively and safely in three ways from the first day:

   1. The mucus in the cervix remains thickened under the influence of the hormone levonorgestrel (= safe barrier), so that sperm cannot enter the uterus and fertilise an egg. This means that women also have a certain degree of protection against infections because sperm occasionally carry bacteria.

   2. The lining of the uterus remains thin and does not prepare to implant a fertilised egg. This makes menstruation much shorter and easier, or stops it altogether.

   3. Any sperm that nevertheless get into the uterus are inhibited in function and mobility by the levonorgestrel hormone.

After removal of the hormonal IUS, these effects recede immediately and are no longer detectable. Women can become pregnant (again) in the first cycle after IUS removal.