HDL cholesterol is the portion of cholesterol in your blood carried by high-density lipoprotein particles. Often called “good” cholesterol, HDL absorbs cholesterol from your bloodstream and carries it back to your liver, which flushes it from your body. An optimal HDL level falls between 60 and 80 mg/dL, and levels below 40 mg/dL in men or 50 mg/dL in women are considered a risk factor for heart disease.
How HDL Works in Your Body
Cholesterol doesn’t dissolve in blood, so it needs a ride. It travels on protein-wrapped particles called lipoproteins. HDL particles are smaller and denser than other lipoproteins, packed tightly with protein relative to fat. This density is what gives HDL its name and its unique ability to scavenge excess cholesterol.
HDL’s most important job is a process called reverse cholesterol transport. It starts when HDL particles pull cholesterol out of cells in your artery walls, including the foam cells that form dangerous plaque buildup. This is actually the bottleneck of the whole process: getting cholesterol out of those cells and into the bloodstream is the hardest step. Once HDL picks up the cholesterol, enzymes on the particle’s surface convert it into a form that can be packed into the particle’s core. The loaded HDL then delivers its cargo to the liver, where the cholesterol is either converted into bile acids or excreted into your digestive tract and eventually eliminated.
HDL vs. LDL: Why One Is “Good”
LDL (low-density lipoprotein) carries cholesterol from the liver out to the rest of your body. When there’s too much LDL, it deposits cholesterol on artery walls, forming plaque that narrows blood vessels and raises the risk of heart attack and stroke. HDL does the opposite: it pulls that deposited cholesterol away and sends it back to the liver for disposal. Think of LDL as the delivery truck and HDL as the cleanup crew.
LDL makes up most of the cholesterol in your blood. That’s why total cholesterol numbers can look fine even when the balance between LDL and HDL is off. The ratio matters more than the total.
HDL Does More Than Move Cholesterol
Beyond its cleanup role, HDL has anti-inflammatory and antioxidant properties that protect your arteries in several ways. HDL carries enzymes that break down harmful oxidized fats on LDL particles. When LDL gets oxidized, it becomes far more damaging to artery walls. By neutralizing that oxidation, HDL reduces LDL’s ability to trigger plaque formation in the first place.
HDL also helps keep the lining of your blood vessels calm. It blocks the signals that recruit immune cells into artery walls, a key early step in plaque development. Specifically, HDL suppresses the production of sticky molecules on the surface of blood vessel cells that would otherwise grab passing immune cells and pull them inside. This dual action, reducing both oxidation and inflammation, means HDL protects arteries through multiple pathways, not just by hauling cholesterol away.
What Your HDL Number Means
HDL is measured as part of a standard lipid panel blood test. You’ll typically need to fast for 9 to 12 hours beforehand, and blood is drawn from a vein in your arm. Here’s how to read your results:
- Below 40 mg/dL (men) or 50 mg/dL (women): Considered low and a risk factor for cardiovascular disease.
- 60 mg/dL and above: Generally considered protective against heart disease.
- 60 to 80 mg/dL: The ideal range for cardiovascular benefit.
- Above 80 mg/dL: Considered elevated and not necessarily healthier. Very high HDL may not provide additional protection.
That last point surprises many people. For years, the assumption was that higher HDL always meant lower risk. But a large U.S. study of nearly 24,000 adults found that higher HDL levels were not associated with reduced cardiovascular disease risk for either Black or white participants. The protective association with low HDL also varied by race: low HDL predicted increased heart attack risk in white adults but not in Black adults. These findings suggest HDL’s relationship to heart disease is more complex than a simple “more is better” equation.
How to Raise Low HDL
If your HDL is below the recommended threshold, lifestyle changes are the first line of action, and combining several of them produces the biggest effect. A healthy diet paired with weight loss and regular exercise can raise HDL by 10% to 13%.
Exercise is one of the most reliable ways to boost HDL. A review of 28 randomized trials found that moderate to high-intensity aerobic exercise produced an average 4.6% increase in HDL levels. That translates to roughly 2 to 3 mg/dL for someone starting at a typical level. The key is consistency rather than intensity: regular activity over weeks and months matters more than occasional hard workouts.
Diet plays a significant role too. Keeping saturated fat to about 7 to 10% of your daily calories while ensuring 15 to 20% of calories come from unsaturated fats (found in olive oil, nuts, avocados, and fatty fish) supports healthy HDL levels. Quitting smoking, if you smoke, raises HDL by about 4 mg/dL on average. Moderate alcohol consumption has been associated with higher HDL, though no medical guidelines recommend starting to drink for this purpose.
When Low HDL Has a Genetic Cause
Some people have persistently low HDL despite a healthy lifestyle. In rare cases, this is caused by inherited genetic mutations. A condition called familial HDL deficiency results from mutations in either the ABCA1 gene or the APOA1 gene. These genes control how cholesterol and fats are released from cells to form HDL particles. When they don’t function properly, the body simply can’t produce enough HDL, regardless of diet or exercise.
A more severe form of this problem is Tangier disease, where both copies of the ABCA1 gene are affected. People with Tangier disease have extremely low or nearly absent HDL levels. These conditions are uncommon, but they illustrate why some individuals struggle with low HDL numbers even when doing everything right. If your HDL remains stubbornly low despite sustained lifestyle changes, genetic factors may be worth exploring with your doctor.