Does flaxseed oil thin the blood?

Yes, it may...: Flaxseed oil is high in polyunsaturated fats and linolenic acid. It has been studied to raise the good HDL cholesterol. Webmd lists increased bleeding as a side effect and recommends stopping it for two weeks before or after any surgery. It should not be used however as a substitute for a blood thinner where needed, like after a stent or for treating atrial fibrillation for example.