Levonorgestrel
"I had mirena from February 2015, to help with heavy bleeding (but periods were regular). After four weeks I started having unpredictable flooding episodes, with frighteningly huge clots, and quickly became anaemic. After six months the bleeding was if anything worse so I insisted the mirena was removed. Six weeks  after removal I am bleeding more often than not, but with less flooding and clotting. It will surely take a while for my system to adjust, to get into cycles again, after being messed with quite so dramatically. If my doctor had indicated that mirena might in some cases make bleeding worse, and become frustratingly unpredictable, I wouldn't have gone ahead."