When your blood has too much LDL, the cholesterol may combine with other substances to form plaques on the walls of your arteries. The plaques make your arteries narrow and less flexible, which leads to a condition called atherosclerosis.
A high LDL level is a risk factor for cardiovascular disease, so it is often called bad cholesterol. HDL cholesterol is considered good cholesterol. Eating a diet high in saturated fats and trans-fats may increase your LDL levels.