A lipid which higher organisms use in the construction of cell membranes and as a precursor molecule in steroid synthesis. If a person produces too much cholesterol, the excess often gets laid down on the interior of blood vessels as plaque, causing heart disease, hardening of the arteries, and often heart attacks or strokes. Cholesterol is carried through the bloodstream in molecules called lipoproteins. There are two major types: low density lipoproteins (LDLs, also known as "bad" cholesterol) and high density lipoproteins (HDLs, aka "good" cholesterol). When your doctor measures your cholesterol, he takes readings of the different types of cholesterol in your blood: Total Cholesterol Desirable: less than 200 mg/dl Borderline High: 200-239 mg/dl High: more than 240 mg/dl LDL Cholesterol Desirable: less than 130 mg/dl Borderline High: 130-159 mg/dl High: more than 160 mg/dl HDL Cholesterol Desirable: more than 35 mg/dl Risk Level: less than 35 mg/dl Those with high cholesterol are generally advised to engage in aerobic exercise, lose weight (if they are overweight), avoid eating foods high in saturated fats and cholesterol, and quit smoking (smoking raises the amount of LDL in the blood). Having elevated amounts of triglycerides in your blood may also increase the risk of heart disease (a normal reading is less than 200 mg/dl). You can generally lower the amount of triglyceride in your blood by exercising, eating a low-fat diet, and losing weight.