Mirena (levonorgestrel) side effects? what are they? when should call doctor?

Not many: The most common side effects would be breakthrough bleeding the first 3 months. This is true for almost all IUDs and hormonal systems tho. Also, cramping. This subsides for the majority after a week or so. It is very controllable with NSAIDs like ibuprofen. Complications include perforation, infection, embedding in uterus, falling out. All of those are rare. I place MANY. My Pts like them.