deep vein thrombosis
"Not many people take this drug for my condition (Antiphospholidid Syndrome) in the UK, so I'm what you might call an 'experiment', but I begged and pleaded to go on it as I'd had enough of taking warfarin, my INR was never steady and I was having blood tests taken every week sometimes. 
It does have some not so good side effects. When I first started taking it, I felt dizzy and faint within a couple of hours, so my haematologist suggested I take it just before bed instead of in the morning which solved the problem. It makes me more tired than before I was on it and I don't have as much energy. I've always been a stressful person and have noticed I seem to get more anxiety now. 
The good outweighs the bad though, I've had no more mini-strokes, so it's doing its job!"