Total cholesterol is the sum of all cholesterol fractions in the blood: LDL cholesterol, HDL cholesterol, VLDL cholesterol, and other minor components. Cholesterol is a waxy fat essential for cell membrane structure, steroid hormone synthesis, bile acid production, and vitamin D synthesis. It is carried in the blood by lipoprotein particles.

Total cholesterol alone is a limited cardiovascular risk marker because it does not distinguish between atherogenic (LDL, VLDL) and protective (HDL) fractions. A high total cholesterol driven by high HDL carries a very different risk profile to the same total driven by high LDL. For this reason, a full lipid panel including LDL, HDL, triglycerides, and non-HDL cholesterol is required for meaningful cardiovascular risk assessment.