Does Cymbalta contain blood a thinner?

No... it's not an official side effect. However it shouldn't be mixed with blood thinners and new side-effects are still being reported. I have been on Cymbalta for a few years (shortly after it came out) and the known side effects then (2005) was a much shorter list than it is today. I've had problems with stomach bleeding from taking it with ibuprofen as well as syncope due from severe hypotension(low blood pressure) because of the cymbalta. Also, the higher the dose, the more pronounced the side effects are. I am prescribed the highest dose (120mg daily) but I typically only take 60-90mg.