Mirena IUD for heavy periods

The hormonal IUD, Mirena® is used for the treatment of heavy periods or excessive menstrual bleeding (also called menorrhagia). Over time the use of Mirena® greatly reduces menstrual flow for many women.

How does the hormonal IUD work?

When Mirena® is placed inside the womb (uterus), it slowly releases the hormone, progestogen directly onto the lining of the uterus, making it thinner and less likely to bleed. In this way, it reduces heavy periods.  

How long does it take to work?

It can take several months for the hormonal IUD device to have its full effect, but by six months after placement, most women will have only light bleeding, or sometimes no bleeding at all. The total blood loss per cycle slowly decreases with continued use.

The number of spotting and bleeding days may increase when you first have it inserted but then usually decrease in the months that follow. Bleeding may also continue to be irregular.

Who should not use the hormonal IUD 

Mirena® is unsuitable in women who have:

  • pelvic infection
  • cancer of the breast, uterus (womb), cervix, or ovary
  • a history of a heart attack or stroke.
  • blood clot problems such as deep vein thrombosis.

Other considerations

  • Cost — Mirena® is only funded for certain conditions.
  • If you have become iron deficient or anaemic from heavy periods, you may be able to receive a funded Mirena.
  • Otherwise, it is not government subsidized in New Zealand and costs about $460 to buy (January 2016).
  • Once fitted, Mirena lasts for up to 5 years. 

Possible side effects

Like all medicines, the IUD can cause unwanted side effects, although not everyone gets them.

Side effects What should I do?
  • Pain
  • Dizziness
  • Feeling weak, feeling faint
  • This is quite common immediately after the IUD is inserted
  • If these symptoms continue for more than a day, contact your doctor   
  • Heavy, painful periods that last longer than usual
  • Breast tenderness, pain or swelling
  • Weight gain
  • This tends to be in the first few months after insertion of the IUD and often settles with time
  • If troublesome, or ongoing discuss with your doctor or nurse

  • Signs of infection such as pain in the lower abdomen or stomach area, fever, flu-like symptoms, feeling unwell, dizziness, feeling faint or vaginal discharge
  • There is a small risk of infection especially within the first 20 days after insertion
  • Tell your doctor or nurse immediately or ring HealthLine 0800 611 116    
  • Risk of expulsion (the IUD may come out by itself)
  • The IUD may come out by itself, because of muscular contractions of the womb 
  • Tell your doctor if you think this has happend 

Learn more

The following links provide further information about Mirena®.


  1. Stewart A, Cummins C, et al. The effectiveness of the levonorgestrel-releasing intrauterine system in menorrhagia: a systematic review. BJOG. 2001 Jan;108(1):74-86.
Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft