Cholesterol tests attempt to measure the amount of cholesterol you have in your blood. Cholesterol is a waxy substance that is not soluble in water. To travel freely in the bloodstream, cholesterol must be bound to special proteins called lipoproteins. The two most common lipoproteins are high-density lipoprotein, HDL, and low-density lipoprotein, or LDL. Cholesterol tests measure the amounts of lipoprotein to indirectly ascertain the amount of cholesterol your body is transporting.
Lipoproteins
Lipoproteins are compounds that allow fat-soluble molecules to move within a mostly water-filled environment. Cholesterol is stored within the core of a lipoprotein and the core is surrounded by phospholipids that protect the cholesterol from the outside environment. There are different types of lipoproteins including LDL and HDL. Density of the lipoprotein depends on the ratio of protein to lipid within the molecule. Lipoproteins with more protein are denser than lipoproteins containing large amounts of fat, or lipid.
HDL
HDL is often called "good cholesterol," as it is able to pick up excess cholesterol in the blood before it can enter the blood vessels and cause damage. Furthermore, HDL transports the cholesterol to the liver where it is broken down and excreted. HDL cholesterol is able to protect your cardiovascular system from complications associated with high levels of LDL or total cholesterol. For adults of both sexes, HDL levels should ideally by 60 mg/dL or greater. Men with HDL levels less than 40 mg/dL or women with less than 50 mg/dL are at a greater risk of heart disease.
LDL
LDL contains the more cholesterol than any other lipoprotein. LDL is considered "bad" cholesterol because high levels of LDL often lead to obstruction of your arteries. LDL can enter the arteries and cause the formation of a plaque that causes the arteries to narrow and harden. This leads to a decrease of blood flow to the organs of your body. You want your LDL levels to be less than 100 mg/dL, but if you are at risk for heart disease then your LDL level should be less than 70 mg/dL. Levels greater than 190 mg/dL are extremely high and greatly increase your chances of suffering from heart attack or stroke.
Total Cholesterol
Total cholesterol is a value that includes HDL, LDL and triglyceride levels. Triglycerides are molecules that contain large amounts of fat. Doctors prefer that your total cholesterol level is less than 200 mg/dL. Total cholesterol levels greater than 240 mg/dL are considered dangerously high, especially if your LDL levels are elevated. However, if your total cholesterol is high due to high HDL levels, then you are at less risk of heart disease.
