HDL stands for high-density lipoprotein, a type of cholesterol-carrying particle in your blood that helps remove excess cholesterol from your arteries. It’s often called “good cholesterol” because higher levels are generally linked to a lower risk of heart disease. Your HDL level is measured as part of a standard cholesterol blood test, and ideally falls between 60 and 80 mg/dL for heart protection.
What HDL Actually Does in Your Body
HDL particles act as cholesterol scavengers. They travel through your bloodstream, pick up excess cholesterol from the walls of your arteries and other tissues, and carry it back to your liver. Your liver then converts that cholesterol into bile acids and flushes it out of your body. This cleanup process is called reverse cholesterol transport, and it’s the primary reason HDL is considered protective.
The process works through specialized transporter proteins on the surface of your cells. These transporters hand off cholesterol molecules to HDL particles passing by. Once HDL picks up cholesterol, an enzyme on the particle’s surface converts it into a form that gets packed into the particle’s core, freeing up room on the surface to collect even more cholesterol. The loaded-up HDL then delivers its cargo to the liver, where a receptor pulls the cholesterol out of the particle.
HDL can also transfer some of its cholesterol to LDL particles, which then get cleared by the liver through a separate pathway. So even indirectly, HDL helps move cholesterol toward elimination.
HDL vs. LDL: Why the Distinction Matters
LDL (low-density lipoprotein) carries cholesterol from the liver out to your tissues. When there’s too much LDL, cholesterol accumulates in artery walls and forms plaques that narrow blood vessels. HDL does the opposite, pulling cholesterol away from those walls. Think of LDL as delivery and HDL as removal. Heart disease risk rises when you have too much delivery and not enough removal.
A 21-year study tracking 8,000 men found that those with low HDL had a 36 to 38% higher risk of dying from coronary heart disease, regardless of whether their total cholesterol was high or normal. Among men with diabetes, the risk jumped to 65% higher compared to diabetics with adequate HDL levels.
What Your HDL Number Means
HDL is measured through a blood test, typically as part of a lipid panel that also checks your total cholesterol, LDL, and triglycerides. You’ll need to fast for 9 to 12 hours beforehand for accurate results.
The reference ranges differ slightly by sex:
- Men: HDL should not fall below 40 mg/dL. The protective range is 60 to 80 mg/dL.
- Women: HDL should not fall below 50 mg/dL. The same 60 to 80 mg/dL range is considered ideal.
If your HDL consistently measures below these floors, your doctor will likely flag it as a cardiovascular risk factor worth addressing.
Very High HDL Isn’t Always Better
For years, the assumption was that higher HDL is always protective. Recent research complicates that picture. A systematic review and meta-analysis found that people with very high HDL levels don’t have lower rates of death from heart disease compared to those with normal levels. In fact, a dose-response analysis revealed that cardiovascular death risk starts climbing again at HDL levels above 94 mg/dL in men and above 116 mg/dL in women. HDL above 80 mg/dL may not be healthy, and the relationship between HDL and mortality appears to follow a U-shaped curve, where both very low and very high levels carry risk.
How to Raise Low HDL
Unlike LDL, which responds well to medication, there are no drugs currently recommended specifically to raise HDL for better heart outcomes. Medications that were once used for this purpose, like niacin and fibrates, have not been shown to reduce cardiovascular events when added to standard therapy. Niacin in particular carries significant side effects including liver toxicity and increased insulin resistance. Current cardiovascular guidelines focus on lowering LDL as the primary treatment target, not raising HDL.
That leaves lifestyle changes as the main lever for improving HDL, and they work well:
- Exercise: As little as 60 minutes of moderate aerobic activity per week can raise HDL while lowering triglycerides. Walking, cycling, and swimming all count.
- Quit smoking: Smoking directly lowers HDL levels, with a particularly strong effect in women. Quitting reverses this.
- Improve your diet: A diet rich in vegetables, fruits, and whole grains supports HDL. Avoiding trans fats is especially important, as they simultaneously raise LDL and lower HDL. Limiting saturated fat from red meat and full-fat dairy also helps.
- Moderate alcohol: Moderate drinking (up to one drink a day for women, two for men) is associated with higher HDL. But this isn’t a reason to start drinking if you don’t already.
- Lose excess weight: Carrying extra body fat, particularly around the midsection, is strongly linked to low HDL. Even modest weight loss can improve your numbers.
What HDL Is Made Of
HDL particles are the smallest and densest of the lipoproteins in your blood, which is where the “high-density” name comes from. Each particle has a shell made of phospholipids (a type of fat that forms cell membranes) and a key protein called apoA-I, which gives HDL its structure and drives its cholesterol-collecting function. The core fills with cholesterol esters, the packaged form of cholesterol ready for transport. HDL also carries sphingomyelin and other specialized lipids on its surface.
People with low HDL levels tend to have altered lipid compositions in their particles, with higher triglycerides and lower levels of certain protective surface lipids. This suggests that HDL quality, not just quantity, plays a role in cardiovascular protection.