Triglycerides are a type of fat in the bloodstream and fat tissue. Too much of this type of fat can contribute to the hardening and narrowing of your arteries, increasing the risk of heart attack or stroke. High triglycerides can be caused by diabetes, obesity, kidney failure or alcoholism. Often, high triglycerides occur along with high levels of cholesterol. Triglyceride and cholesterol levels are measured as part of a blood test. Normal triglyceride levels are below 150. Levels above 200 are high.