Answers by TheMediTary.Com - Last updated: 13-Jul-2023
The side effects for Mirena list that there may be an alteration of menstrual bleeding and an increase in genital discharge.
In our comments section, where real people leave reviews, women do mention having a brownish discharge so it appears to be a normal side effect.
For the Mirena comments section which you may find useful see:
https://www.drugs.com/comments/levonorgestrel/mirena.html
For more information on Mirena see:
https://www.drugs.com/pro/mirena.html