By Mayo Clinic Staff

High-density lipoprotein (HDL) cholesterol helps remove other forms of cholesterol from the bloodstream. That's why it's often called the "good" cholesterol.

Cholesterol is a waxy substance found in every cell in the body. Your body needs cholesterol to build healthy cells and make certain hormones. Cholesterol travels through the bloodstream attached to proteins called lipoproteins.

The two main types of lipoproteins that carry cholesterol are:

• Low-density lipoprotein (LDL) cholesterol. Too much LDL cholesterol can build up inside the walls of your blood vessels over time. This buildup narrows the blood vessels and reduces blood flow. Sometimes a clot forms. The blockage can cause a heart attack or stroke. This is why LDL cholesterol also is called the "bad" cholesterol.

• High-density lipoprotein cholesterol. HDL cholesterol is often called the "good" cholesterol. That's because it helps remove excess cholesterol from your bloodstream. HDL cholesterol carries excess cholesterol from the bloodstream to the liver. The liver breaks down the cholesterol and flushes it from the body.

HDL cholesterol levels are often lower in people who have metabolic syndrome. Metabolic syndrome is a group of conditions — including obesity, high blood pressure and high blood sugar — that raises the risk of diabetes and heart disease.

A higher level of HDL cholesterol has long been linked to lower rates of heart disease. But research has shown that simply increasing HDL cholesterol does not necessarily reduce heart attack or stroke risk. Today, healthcare professionals look at HDL as just one part of a person's overall heart disease risk. For most people, raising HDL cholesterol by itself is not a treatment goal.

If your LDL cholesterol is high and your HDL cholesterol is low, your healthcare professional will likely focus on lowering your LDL cholesterol first. Medicines known as statins are the most common treatment for high LDL cholesterol. Examples are atorvastatin (Lipitor) and simvastatin (Zocor).

Medicines used to lower LDL cholesterol and triglyceride levels sometimes improve HDL cholesterol levels. These include prescription niacin; fibrates such as gemfibrozil (Lopid); and certain statins, such as simvastatin and rosuvastatin.

But clinical trials haven't shown that increasing HDL cholesterol levels with medicines reduces the risk of heart attack. So your healthcare professional is likely to suggest boosting HDL cholesterol with lifestyle changes instead.

HDL cholesterol is measured as part of a lipid panel test. Your HDL level is one piece of information your healthcare professional uses to assess your heart disease risk. Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. Or they are measured in millimoles (mmol) of cholesterol per liter (L) of blood.

People who have naturally higher levels of HDL cholesterol are at somewhat lower risk of heart attack and stroke. But research has shown that medicines used just to increase HDL cholesterol levels have not lowered the rate of heart attack. Healthcare professionals now look at HDL as one part of someone's overall heart health rather than a treatment target on its own.

An HDL level below 40 mg/dL for men and below 50 mg/dL for women is considered low and is linked to a higher risk of heart disease. An HDL level of 40 mg/dL or higher for men and 50 mg/dL or higher for women is generally considered acceptable. An HDL level of 60 mg/dL or higher is associated with a lower risk of heart disease.

Very high HDL cholesterol levels aren't always better. HDL cholesterol levels above 100 mg/dL (2.5 mmol/L) are considered extreme. Some research suggests that people with naturally very high HDL cholesterol levels may have a higher risk of heart disease. Researchers are still studying why this happens. Genes may be the cause of naturally very high HDL cholesterol. One hypothesis to explain why high risk is linked to very high HDL is that the HDL may be defective when those genes are present, causing HDL to be very high.

If you have low HDL levels, there are things you can do. The good news is that lifestyle changes can improve your cholesterol numbers and lower the risk of heart attack and stroke. These changes include moving more, quitting smoking, and eating a diet rich in vegetables, fruits and whole grains.

• Move more. Regular physical activity improves heart health in many ways. It can raise HDL cholesterol levels, improve blood pressure and lower triglyceride levels. Triglycerides are the most common type of fat in the body. Aim for 150 minutes a week of moderate aerobic exercise to help improve your heart health.
• Choose healthier fats. Try not to include trans fats in your diet. Trans fats can increase LDL cholesterol and lower HDL cholesterol levels. Foods made with shortening, such as cakes and cookies, often contain trans fats. So do most fried foods and some margarines. Also limit saturated fat, found in meats and full-fat dairy products.
• Quit smoking. If you smoke, quitting is one of the best things you can do for your heart. Smoking lowers HDL levels, especially in women. And it may raise LDL cholesterol and triglyceride levels.
• Be careful with alcohol. Moderate use of alcohol has been linked with higher levels of HDL cholesterol. If you choose to drink alcohol, limit how often you drink and keep the amount small. For overall health, drink one or fewer drinks a day. Do not drink every day. The less you drink, the better. If you don't drink alcohol, don't start drinking to raise your HDL cholesterol levels. Too much alcohol can cause weight gain. And it might increase your blood pressure and triglyceride levels and raise your risk of certain cancers.

HDL levels are sometimes improved by drugs used to lower LDL and triglyceride levels — such as prescription niacin; fibrates such as gemfibrozil (Lopid); and certain statins, particularly simvastatin (Zocor) and rosuvastatin (Crestor).

But clinical trials for several drugs specifically designed to increase HDL levels were halted early because they didn't reduce the risk of heart attacks.

Drugs containing testosterone and other anabolic steroids can lower your HDL cholesterol levels. Avoiding these drugs may help increase your HDL numbers.

Healthcare professionals generally don't prescribe medicines just to raise HDL cholesterol. Medicines that lower LDL cholesterol and triglyceride levels sometimes improve HDL cholesterol levels. These include prescription niacin; fibrates such as gemfibrozil (Lopid); and certain statins, such as simvastatin and rosuvastatin.

But studies haven't shown that raising HDL cholesterol levels with medicines reduces the risk of heart attack. So, your healthcare professional is likely to focus on lowering LDL levels instead.

Treatment for high cholesterol focuses on lowering LDL cholesterol and reducing your overall risk of heart disease and stroke. HDL cholesterol remains important, but treatment isn't aimed at raising HDL levels alone.