血脂是指血液里脂肪含量，通常包括胆固醇（Cholesterol）与三酸甘油酯（Triacylglycerol）。其量度单位为mg/dL。

胆固醇又分为高密度、低密度、非常低密度胆固醇及乳糜粒。胆固醇是一种脂肪的复合体，它是制造重要激素和维生素不可缺少的物质。胆固醇除部份由食物供给外，多数皆由肝脏合成，其理想浓度为小于200mg/dL。胆固醇需要与脂蛋白结合才能被运送到身体各部份。脂蛋白可以分为低密度脂蛋白（LDL-C）和高密度脂蛋白（HDL-C）两种。

三酸甘油酯即是中性脂肪则扮演着贮存与输送的角色，大部分存在于乳糜粒及极低密度脂蛋白内。它是能量的主要来源，极易受到饮食影响。

Blood lipids (or blood fats) are lipids in the blood, either free or bound to other molecules. They are mostly transported in a protein capsule, and the density of the lipids and type of protein determines the fate of the particle and its influence on metabolism. The concentration of blood lipids depends on intake and excretion from the intestine, and uptake and secretion from cells. Blood lipids are mainly fatty acids and cholesterol. Hyperlipidemia is the presence of elevated or abnormal levels of lipids and/or lipoproteins in the blood, and is a major risk factor for cardiovascular disease.