blood low density lipoprotein cholesterol level Measurement of the amount of cholesterol, a eukaryotic sterol that in higher animals is the precursor of bile acids and steroid hormones and a key constituent of cell membranes, carried in low-density lipoprotein (LDL) molecules in a specified volume of blood, the fluid that circulates through the heart, arteries, capillaries and veins carrying nutrients and oxygen to the body tissues and metabolites away from them. LDL constitute a class of relatively large, heterogeneous lipoprotein particles, complex molecules that consist of a protein membrane surrounding a core of lipids. The LDL class of lipoproteins has a density between 1.019 and 1.063 g/ml. In some animal species, such as canine and rodents, this may overlap with the HDL1 class and be designated LDL/HDL1. low density lipoprotein cholesterol measurement blood lipoprotein cholesterol level