HDL cholesterol is a type of cholesterol carried through your bloodstream by small, dense particles called high-density lipoproteins. Often called “good” cholesterol, HDL’s main job is removing excess cholesterol from your arteries and other tissues and shuttling it back to your liver, where it’s either recycled or eliminated through the gallbladder. This cleanup process is the primary reason HDL earned its positive reputation, though the full picture is more nuanced than “higher is always better.”
How HDL Works in Your Body
The process HDL performs is called reverse cholesterol transport. Cholesterol naturally accumulates in blood vessel walls and other peripheral tissues over time. HDL particles act like garbage trucks: they pick up that excess cholesterol, carry it through the bloodstream, and deliver it to the liver for disposal or reuse. Without this system, cholesterol would build up in artery walls much faster, accelerating the formation of plaques that narrow blood vessels.
Each HDL particle is built around a protein called apolipoprotein A-I, which makes up about 70% of the particle’s protein mass. This protein acts as a structural scaffold, wrapping around a core of fats and cholesterol to form a stable, spherical particle. The protein shell also serves as a docking station for enzymes and other molecules that help HDL do its work. Think of it as the frame that holds everything together and determines how well the particle functions.
What Your HDL Number Means
HDL cholesterol is measured as part of a standard lipid panel blood test, reported in milligrams per deciliter (mg/dL). The CDC defines optimal levels as at least 40 mg/dL for men and at least 50 mg/dL for women. Falling below these thresholds is considered a risk factor for cardiovascular disease.
But “good cholesterol” is an oversimplification. A major study supported by the National Heart, Lung, and Blood Institute found that while low HDL predicted increased heart attack risk in white adults, the same association did not hold for Black adults. Even more striking, higher HDL levels were not associated with reduced cardiovascular disease risk for either group. This was the largest U.S. study to demonstrate that simply having more “good” cholesterol may not provide cardiovascular benefits across populations.
Why Very High HDL Can Be a Problem
For decades, the assumption was that higher HDL was always better. Research published in the American Heart Association’s journals tells a different story. The relationship between HDL and cardiovascular risk follows a U-shaped curve: both low and high levels are associated with more cardiovascular events compared to moderate levels.
In a study of patients with high blood pressure, those with HDL above 80 mg/dL had a 3.5% rate of cardiovascular events, nearly matching the 3.4% rate seen in the low-HDL group. The middle group fared best at 2.6%. This increased risk at high levels was confirmed in men but not in women. Researchers believe that at extremely high concentrations, HDL particles may become dysfunctional, losing their protective properties or even becoming harmful through mechanisms that aren’t fully understood yet.
What Lowers HDL
Smoking is one of the most consistent HDL-lowering factors. Smokers reliably have lower HDL than nonsmokers, and even passive exposure to cigarette smoke reduces HDL levels. The good news: quitting smoking effectively raises HDL back up.
Body weight plays a significant role too. HDL levels are inversely related to body mass index, meaning that as weight goes up, HDL tends to go down. High triglyceride levels (another type of blood fat) also pull HDL in the wrong direction, and the two often travel together in people who carry excess weight or eat diets high in refined carbohydrates.
Genetics can also be a factor. Rare inherited conditions like Tangier disease cause severely low HDL due to mutations in a gene responsible for cholesterol transport out of cells. People with Tangier disease can develop nerve problems, enlarged orange-colored tonsils, and cloudy corneas. Less dramatic genetic variations can nudge HDL levels modestly lower without causing obvious symptoms.
How to Raise HDL Naturally
Exercise is the most reliable lifestyle tool for boosting HDL. As little as 60 minutes of moderate aerobic activity per week can raise HDL while simultaneously lowering triglycerides. That’s a brisk walk for about 20 minutes three days a week, which is a low bar compared to most fitness recommendations.
On the dietary side, the biggest lever is avoiding trans fats, which raise LDL (“bad”) cholesterol and lower HDL at the same time. Trans fats still show up in some processed foods, fried items, and certain baked goods. Limiting saturated fat from red meat and full-fat dairy products also helps maintain a healthier cholesterol balance, though the effect on HDL specifically is less dramatic than cutting trans fats.
Why HDL-Raising Medications Haven’t Panned Out
Given HDL’s reputation as protective, pharmaceutical companies spent years developing drugs to raise it. The most studied option, niacin (a B vitamin), can raise HDL by more than 30% and lower triglycerides by 25%. Those numbers sound impressive on paper.
In practice, however, niacin therapy has not been linked to lower rates of death, heart attack, or stroke in most people. When added to standard cholesterol-lowering medications, niacin provides very little additional benefit. Some evidence suggests a narrow exception for people who have both high triglycerides and low HDL, but for most, raising the HDL number itself doesn’t translate into fewer heart attacks. This disconnect is part of why researchers now focus more on HDL particle function (how well HDL does its job) rather than just the total amount measured on a blood test.
The Triglyceride-to-HDL Ratio
Some clinicians look beyond individual numbers and consider the ratio of triglycerides to HDL as a marker of metabolic health. A higher ratio generally signals greater insulin resistance and cardiovascular risk, particularly in women. In one study of women with non-obstructive coronary artery disease, those who went on to develop major cardiovascular events had a median ratio of 2.3, compared to 1.9 in those who did not. Interestingly, this ratio was not significantly different between men who developed cardiovascular events and those who didn’t, suggesting the metric may be more useful in certain populations than others.
You can calculate your own ratio by dividing your triglyceride number by your HDL number from any standard lipid panel. While no single threshold is universally agreed upon, a lower ratio generally reflects a healthier metabolic profile.