Everything you need to know about the Mirena coil

No, the progesterone in the Mirena coil (levonorgestrel) is not body identical. It is a synthetic progestogen, meaning it is designed to mimic the effects of natural progesterone but has a different structure. Body-identical progesterone, such as micronised progesterone (Utrogestan, Gypretix), is molecularly the same as the progesterone your body produces.

There is no strong evidence that the Mirena coil directly causes weight gain. Some people notice fluid retention or changes in appetite, but this is not universal. If you’re concerned about weight changes, it may be helpful to focus on overall lifestyle factors rather than the coil itself.

For contraception, the Mirena coil lasts for 8 years according to current UK guidelines. However, if it was fitted at age 45 or older, it can remain in place until menopause without needing replacement.

When used as part of HRT, the Mirena coil provides the necessary progesterone for only 5 years. After this time, if you’re continuing HRT, you will need either a new coil or an alternative form of progesterone.

The Mirena is fitted by a trained doctor or nurse in a quick outpatient procedure:

1. A speculum (like in a smear test) is used to open the vagina.
2. The cervix is cleaned, and a thin, flexible tube is used to insert the coil into the womb.
3. The strings are trimmed so they sit just inside the vagina for future removal.

The whole process takes a few minutes. Discomfort is normal, but many women find it manageable. You can ask for pain relief, and the coil fitting clinic needs to provide that for you if you request it.

Removal is usually straightforward and takes just a few minutes:

1. A speculum is inserted to find the strings.
2. The doctor or nurse gently pulls on the strings, and the coil slides out.

Most women find this quick and only mildly uncomfortable. If the strings are not visible, a scan may be needed, and removal could be slightly more complex.