HDL cholesterol is a type of cholesterol carried through your bloodstream by high-density lipoproteins, small protein-wrapped particles that pick up excess cholesterol from your tissues and ferry it back to your liver for disposal. It’s often called “good” cholesterol because higher levels are linked to a lower risk of heart disease and stroke. A healthy HDL level is 60 mg/dL or above, while levels below 40 mg/dL in men or 50 mg/dL in women are considered low.
How HDL Differs From LDL
Cholesterol itself is a single fatty substance your body needs to build cells and make hormones. It can’t dissolve in blood, so it travels inside protein shells called lipoproteins. The two main types move cholesterol in opposite directions, and that difference is what makes one protective and the other dangerous.
LDL (low-density lipoprotein) carries cholesterol from the liver out to your tissues. When there’s too much of it, LDL deposits cholesterol on the walls of your arteries, forming a sticky buildup called plaque. Over time, plaque narrows arteries and sets the stage for heart attacks and strokes. HDL works in reverse. It circulates through your blood, absorbs cholesterol from artery walls and other tissues, and carries it back to the liver. The liver then breaks it down and flushes it from the body, mostly through bile that leaves in your stool. This cleanup process is called reverse cholesterol transport.
What HDL Actually Does in Your Body
HDL particles are made up of cholesterol, triglycerides, and a collection of specialized proteins. The most important of these is a protein called Apo-AI, which gives the particle its structure and activates an enzyme that packages loose cholesterol into a form HDL can carry.
The cleanup process works in stages. First, cells lining your artery walls pump out unesterified (free) cholesterol through specific gateways on their surface. HDL particles act as the acceptor, grabbing that cholesterol. Once aboard, an enzyme converts the cholesterol into a more compact form, creating a mature, fully loaded HDL particle. From there, the cholesterol reaches the liver by two routes: HDL can deliver it directly, or it can hand the cholesterol off to other lipoproteins that the liver then absorbs. Either way, the liver converts the cholesterol into bile acids or shuttles it into bile for excretion.
This process is especially important inside atherosclerotic plaques, where immune cells gorge on cholesterol and become “foam cells” that fuel plaque growth. HDL is the main way cholesterol gets pulled back out of those foam cells, which is why higher HDL levels are associated with slower plaque progression.
How Low HDL Affects Heart Disease Risk
Low HDL is an independent risk factor for heart disease, meaning it raises your risk even when your total cholesterol is normal. A 21-year study of 8,000 men found that those with HDL at or below 35 mg/dL had a 37% higher risk of dying from coronary heart disease compared to men with higher HDL, regardless of their total cholesterol. Data from the Helsinki Heart Study showed that for every 1 mg/dL increase in HDL, the risk of a new coronary event dropped by about 3%.
That may sound like a small number per unit, but HDL levels can swing by 10 to 20 mg/dL or more depending on lifestyle, which translates to a meaningful shift in long-term risk.
When HDL Gets Too High
For years, the assumption was that more HDL is always better. Recent data from the UK Biobank complicates that picture. HDL levels above 80 mg/dL were associated with an 11% higher risk of death from any cause and a 24% higher risk of cardiovascular death after adjusting for other factors. Notably, this increased risk appeared only in men. Women with HDL above 80 mg/dL showed no increased risk.
The reasons aren’t fully understood, but the finding suggests that extremely high HDL isn’t necessarily protective and may signal other metabolic issues. The practical sweet spot appears to be between 60 and 80 mg/dL for most people.
Optimal Levels by Age and Sex
For adults 20 and older, 60 mg/dL or higher is considered the best range. The thresholds for “low” differ by sex: below 40 mg/dL is low for men, and below 50 mg/dL is low for women. Women tend to have naturally higher HDL levels than men, partly due to the influence of estrogen, which is why the low cutoff is set higher.
HDL is measured as part of a standard lipid panel, which your doctor can order as a simple blood draw. Most guidelines recommend getting your first lipid panel in your early 20s and rechecking every four to six years if results are normal.
Exercise and Its Effect on HDL
Aerobic exercise is the single most effective lifestyle change for raising HDL. The gains depend on how hard and how often you work out. In one 16-week study, participants who progressed from 30-minute sessions three times per week to 45-minute sessions four times per week saw their HDL rise from 54 to 69 mg/dL, a jump of about 28%. They also lost 13% of their body fat, which likely amplified the effect.
A longer, 8-month trial of sedentary, overweight adults found that jogging roughly 20 miles per week at moderate-to-vigorous intensity raised HDL from about 44 to 49 mg/dL while also lowering triglycerides by nearly 17%. Even a 6-month program starting at moderate intensity and building up showed significant improvements in the ratio of total cholesterol to HDL, a number many cardiologists consider more telling than HDL alone.
You don’t need to run marathons. The consistent finding across studies is that regular, sustained aerobic activity (brisk walking, cycling, swimming) done at least three times a week produces measurable HDL improvements within a few months.
Diet Changes That Raise HDL
The type of fat you eat matters more than the total amount. Replacing saturated fats (butter, full-fat cheese, bacon, lard) and trans fats (some margarines, fried foods, processed baked goods) with unsaturated fats reliably nudges HDL upward. Good sources of unsaturated fat include avocados, olive oil, nuts, and fatty fish.
Cutting back on refined carbohydrates and added sugar also helps, because excess sugar drives up triglycerides, which tend to move inversely with HDL. When triglycerides go up, HDL usually drops. Fiber-rich foods like oatmeal and beans support the opposite pattern, helping bring triglycerides down and HDL up.
Medications for Low HDL
Most cholesterol drugs are designed to lower LDL rather than raise HDL, and the options for specifically boosting HDL are limited. Niacin (vitamin B3) in prescription doses is the most effective, raising HDL by roughly 8 to 12% depending on the dose. However, a major clinical trial called AIM-HIGH found that even though niacin successfully raised HDL in patients already taking statins, it didn’t reduce heart attacks, strokes, or deaths. That result cooled enthusiasm for prescribing niacin purely to raise HDL numbers.
Fibrates, another class of cholesterol drugs, raise HDL by about 4 to 6% and are more commonly used to lower triglycerides. Statins, despite being the most widely prescribed cholesterol medication, have almost no effect on HDL. In one study, atorvastatin raised HDL by less than 1%, a change that was not statistically meaningful.
The current thinking in cardiology leans toward improving HDL through exercise and diet rather than relying on drugs to push the number up. The benefit of HDL appears to come from how well it functions (its ability to pull cholesterol out of artery walls) rather than simply how much of it is circulating. A high HDL number produced by medication doesn’t necessarily mean the particles are doing their job more effectively.