Hi, Brown spotting while on Mirena IUD is a common side effect and is usually not a cause for concern. Mirena works by releasing a hormone called progestin which can thin the lining of the uterus, making it less likely to have a period. However, it is common to experience irregular bleeding or spotting, especially during the first few months after insertion. In your case, the severe cramps and brown spotting could be due to hormonal changes related to the IUD. The Mirena may be causing some irritation or inflammation in the uterus or cervix, which can result in cramping and spotting. However, if the symptoms persist or become more severe, it is important to see your healthcare provider to rule out any other potential causes, such as infection or injury to the uterus. In general, if you experience any unusual or concerning symptoms while using Mirena, it is always a good idea to talk to your healthcare provider. They can provide more information about possible side effects and help you decide whether any further testing or treatment is necessary. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician