Serum LDL is a cholesterol-rich lipoprotein in the body, and serum LDL is usually classified as high-density cholesterol and low-density cholesterol. Low LDL usually means malnutrition or abnormal liver function, because low LDL may be due to abnormal synthesis of LDL by the liver and kidneys, or low LDL may be due to inadequate nutritional intake and fat supplementation. High LDL can cause increased blood viscosity and atherosclerosis, and may also lead to stroke and cardiovascular disease. It is important to be alert when LDL abnormalities occur. Both high and low LDL can have an effect on the body and usually requires improvement through diet and exercise.