Low-density lipoprotein (LDL) is the type of cholesterol that can become dangerous if you have too much of it. Like gunk clogging up your kitchen drain, LDL cholesterol can form plaque and build up in the walls of your arteries. This can make your arteries narrower and less flexible, putting you at risk for conditions like a heart attack or stroke. Optimally, LDL levels should be less than 100 mg/dl. Near-optimal levels range from 100 to 129 mg/dl and borderline high from 130 to 159 mg/dl. A score greater than 160 mg/dl is high and greater than 190 mg/dl is very high. Your physician can measure your cholesterol levels.