HDL and LDL are two types of cholesterol-carrying particles in your blood. LDL (low-density lipoprotein) moves cholesterol from the liver out to your tissues and arteries, where it can build up. HDL (high-density lipoprotein) does the opposite, pulling cholesterol out of your arteries and ferrying it back to the liver for disposal. Together, they determine much of your cardiovascular risk.
How LDL and HDL Work Differently
Your body needs cholesterol to build cell membranes, produce hormones, and make vitamin D. It can’t travel through your bloodstream on its own because it’s fatty and blood is water-based. So your liver packages cholesterol inside protein-coated particles called lipoproteins. The two main types, LDL and HDL, move cholesterol in opposite directions.
LDL particles carry cholesterol away from the liver and deliver it to cells throughout the body. This is necessary, but when there’s more LDL cholesterol circulating than your cells need, the excess can lodge in artery walls and trigger inflammation. Over time, that buildup forms plaques that narrow and stiffen arteries, a process called atherosclerosis. This is why LDL is commonly called “bad” cholesterol. It makes up most of the cholesterol in your blood.
HDL particles work as a cleanup crew. They pick up excess cholesterol from artery walls, including from the foam cells that form inside plaques, and transport it back to the liver. From there, the liver converts it into bile and the body excretes it through the intestines. About 25% of the cholesterol removed this way leaves through bile, and roughly a third exits through a separate pathway directly through the intestinal wall. This entire return trip is called reverse cholesterol transport, and it’s HDL’s central job.
What Your Numbers Mean
When you get a lipid panel, you’ll see separate values for LDL cholesterol, HDL cholesterol, total cholesterol, and triglycerides. Current guidelines from the American Heart Association and American College of Cardiology don’t use a single “optimal” LDL number for every adult. Instead, they assess your overall cardiovascular risk and set targets based on that. Someone with diabetes and high blood pressure will have a much lower LDL goal than a healthy 35-year-old with no risk factors.
That said, some general benchmarks are useful. An LDL of 190 mg/dL or higher is classified as severe hypercholesterolemia and almost always warrants treatment regardless of other factors. For adults with LDL between 70 and 189 mg/dL, the decision to treat depends on a 10-year risk calculation that factors in age, blood pressure, kidney function, diabetes status, and other variables.
For HDL, higher is generally better, but only up to a point. HDL below 40 mg/dL is considered low and signals increased cardiovascular risk. Observational research has found that extremely high HDL levels (above roughly 90 mg/dL in women and 70 mg/dL in men) are actually associated with increased risk of death from non-cardiovascular causes and higher rates of infection. The old assumption that “the higher your HDL, the better” doesn’t hold at the extremes.
Why Non-HDL Cholesterol Matters
Your lab results may also include a number called non-HDL cholesterol. This is simply your total cholesterol minus your HDL. It captures all the cholesterol riding on potentially harmful particles, not just LDL but also other types like VLDL and remnant particles that contribute to plaque formation.
Non-HDL cholesterol is a better predictor of cardiovascular disease than LDL alone because it accounts for a wider range of harmful particles. It’s especially informative if you have high triglycerides, metabolic syndrome, obesity, or type 2 diabetes, all conditions where LDL alone can underestimate your actual risk. If your doctor has put you on a cholesterol-lowering medication and your LDL looks good but your non-HDL is still elevated, that gap reflects residual risk that may need attention.
What Raises or Lowers Each Type
Diet, exercise, body weight, and genetics all influence your LDL and HDL levels, sometimes in different directions.
Saturated fat and trans fat in the diet raise LDL. Replacing them with unsaturated fats (found in olive oil, nuts, and fatty fish) lowers it. Soluble fiber from oats, beans, and fruits also pulls LDL down modestly. Regular aerobic exercise tends to raise HDL while lowering LDL and triglycerides. Carrying excess weight, particularly around the midsection, typically suppresses HDL and raises LDL. Smoking lowers HDL; quitting raises it.
Genetics play a significant role that lifestyle alone can’t always overcome. Familial hypercholesterolemia (FH) is an inherited condition that causes very high LDL from birth. It comes in two forms: one inherited from one parent (heterozygous) and a rarer, more severe form inherited from both parents (homozygous). People with FH can have LDL levels well above 190 mg/dL even with a healthy diet. Another inherited factor is a particle called lipoprotein(a), or Lp(a). Your Lp(a) level is almost entirely determined by your genes, and when it’s high, it independently increases cardiovascular and stroke risk. Unlike LDL, Lp(a) doesn’t respond much to diet or exercise, so it’s worth knowing your level, especially if heart disease runs in your family.
Why Raising HDL Hasn’t Worked as Treatment
Given HDL’s cleanup role, it seemed logical that drugs raising HDL levels would prevent heart attacks. Multiple clinical trials tested this idea, and none of them showed improved cardiovascular outcomes from pharmacologically boosting HDL. The current understanding is that HDL’s function, how efficiently it removes cholesterol, matters more than the raw number on a blood test. Two people with the same HDL level can have very different levels of protection depending on how well their HDL particles actually work.
This is why treatment strategies focus primarily on lowering LDL rather than raising HDL. Lifestyle changes that raise HDL (exercise, weight loss, not smoking) carry so many other benefits that they’re still recommended, but the direct treatment target on your lab work is almost always LDL or non-HDL cholesterol.
Reading Your Lipid Panel in Context
A lipid panel gives you four or five numbers, and no single number tells the whole story. Your LDL, HDL, triglycerides, and non-HDL cholesterol interact with each other and with your broader health profile. A moderately elevated LDL in a young, otherwise healthy person carries a very different meaning than the same number in someone with diabetes and a family history of early heart attacks.
Current guidelines calculate your 10-year risk of cardiovascular disease and sort it into categories: low (below 3%), borderline (3% to just under 5%), intermediate (5% to under 10%), and high (10% or above). Where you fall on that scale, combined with your specific cholesterol numbers, determines how aggressively your levels need to be managed. The numbers on the page are a starting point for that conversation, not a verdict on their own.