Cholesterol is a type of lipid. It’s a waxy, fat-like substance that your liver produces naturally. It’s vital for the formation of cell membranes, certain hormones, and vitamin D.

Cholesterol doesn’t dissolve in water, so it can’t travel through your blood on its own. To help transport cholesterol, your liver produces lipoproteins.

Lipoproteins are particles made from fat and protein. They carry cholesterol and triglycerides (another type of lipid) through your bloodstream. The two major forms of lipoprotein are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

If your blood contains too much LDL cholesterol (cholesterol carried by low-density lipoprotein), it’s known as high cholesterol. When left untreated, high cholesterol can lead to many health problems, including heart attack or stroke.

High cholesterol typically causes no symptoms. That’s why it’s important to get your cholesterol levels checked on a regular basis. Learn what cholesterol levels are recommended for your age.