LDL and HDL are both cholesterol carriers in your blood, but they move cholesterol in opposite directions. LDL delivers cholesterol from your liver to your tissues and arteries, while HDL picks up excess cholesterol and carries it back to the liver for disposal. This is why LDL is called “bad” cholesterol and HDL is called “good” cholesterol, though the full picture is more nuanced than those labels suggest.
What LDL and HDL Actually Do
Cholesterol itself isn’t inherently harmful. Your body needs it to build cell membranes, produce hormones, and make vitamin D. But cholesterol can’t dissolve in blood, so it travels inside protein-wrapped particles called lipoproteins. LDL (low-density lipoprotein) and HDL (high-density lipoprotein) are simply two different types of these delivery vehicles, each with a different job.
LDL carries cholesterol outward from the liver to cells throughout the body. When there’s too much LDL circulating, the excess particles start accumulating in the walls of your arteries. Once trapped there, LDL particles become oxidized and trigger an immune response: white blood cells rush in, swallow the modified cholesterol, and form fatty streaks that gradually harden into plaque. This process, called atherosclerosis, narrows your arteries and is the primary driver of heart attacks and strokes.
HDL works in the opposite direction. It acts as a cholesterol scavenger, pulling excess cholesterol away from artery walls and other tissues, then ferrying it back to the liver. The liver converts that cholesterol into bile acids and either recycles or eliminates them. This cleanup process, known as reverse cholesterol transport, is why higher HDL levels are associated with lower cardiovascular risk.
How Plaque Builds Up
The damage from excess LDL doesn’t happen overnight. It’s a slow, self-reinforcing cycle. LDL particles first bind to molecules in the inner lining of artery walls, where they become trapped. Once stuck, they’re chemically modified through oxidation and clumping. These modified particles irritate the artery lining and attract immune cells, particularly a type of white blood cell called a macrophage.
Macrophages engulf the oxidized LDL and balloon into what pathologists call “foam cells,” the building blocks of arterial plaque. These foam cells release inflammatory signals and reactive molecules that damage the artery further, causing even more LDL to accumulate. Over years and decades, the plaque grows, stiffens, and can eventually rupture, triggering a blood clot that blocks the artery entirely.
HDL helps interrupt this cycle at multiple points. By removing cholesterol from artery walls before it can be oxidized, HDL essentially counteracts the accumulation that LDL causes. This tug-of-war between LDL depositing cholesterol and HDL removing it is a central factor in your cardiovascular health.
Optimal Levels for Each
When you get a standard lipid panel, you’ll see separate numbers for LDL, HDL, total cholesterol, and triglycerides. The CDC considers these levels optimal for most adults:
- LDL: Around 100 mg/dL
- HDL: At least 40 mg/dL for men, 50 mg/dL for women
- Total cholesterol: Around 150 mg/dL (above 200 mg/dL is considered high)
- Triglycerides: Less than 150 mg/dL
These are general benchmarks. If you already have heart disease, diabetes, or other risk factors, your target LDL may be significantly lower. The numbers also don’t tell the whole story on their own. Many clinicians now consider non-HDL cholesterol, which is simply your total cholesterol minus your HDL, to be a better predictor of heart disease risk than LDL alone. Non-HDL cholesterol captures all the harmful cholesterol-carrying particles in a single number, not just LDL.
When Genetics Override Lifestyle
Most people with high LDL can trace it to diet, inactivity, or weight. But some people inherit a condition called familial hypercholesterolemia (FH) that keeps their LDL dangerously high regardless of how well they eat or exercise. The genetic defect impairs the liver’s ability to clear LDL from the blood, so it accumulates from birth.
FH is worth knowing about because the risk it carries is dramatically higher than lifestyle-driven high cholesterol. Adults with LDL persistently above 190 mg/dL who don’t carry the FH gene mutation face roughly a 6-fold increased risk of coronary artery disease compared to people with LDL under 130 mg/dL. Those with the same LDL level who do carry the mutation face a 22-fold increased risk, likely because their arteries have been exposed to excess cholesterol since childhood. Screening guidelines recommend considering FH in adults with LDL above 190 mg/dL and in children with LDL persistently above 160 mg/dL, especially when there’s a family history of early heart disease.
How to Raise HDL and Lower LDL
Exercise is one of the most reliable ways to boost HDL. Aim for at least 30 minutes of moderate activity like brisk walking five days a week, or 25 minutes of vigorous activity like running or fast cycling three days a week. Both patterns produce measurable increases in HDL over time.
Diet changes primarily target LDL. Replacing saturated fats (found in red meat, butter, and full-fat dairy) with unsaturated fats (olive oil, nuts, avocados, fatty fish) reduces the amount of LDL your liver produces. Soluble fiber, found in oats, beans, and certain fruits, binds cholesterol in the gut and prevents it from being absorbed. Losing excess weight improves both numbers simultaneously, lowering LDL while raising HDL.
Smoking lowers HDL, so quitting typically leads to a noticeable rebound in HDL levels within weeks to months. Alcohol in moderate amounts has been linked to slightly higher HDL, but the cardiovascular risks of drinking generally outweigh this small benefit.
When lifestyle changes aren’t enough, particularly for people with very high LDL or existing heart disease, cholesterol-lowering medications can reduce LDL by 30% to 50% or more. These are most effective when combined with the dietary and exercise changes described above, not used as a substitute for them.
Why the Ratio Between Them Matters
Your individual LDL and HDL numbers are useful, but the balance between them paints a clearer picture of risk. Someone with an LDL of 130 and an HDL of 70 is in a very different position than someone with an LDL of 130 and an HDL of 35. In the second case, there’s far less HDL available to counteract the cholesterol being deposited by LDL.
Rather than calculating a formal ratio, many clinicians now simply look at non-HDL cholesterol as a single metric. You can figure this out yourself: subtract your HDL number from your total cholesterol. The result captures the combined contribution of all harmful cholesterol particles. For most people, keeping that non-HDL number low while maintaining healthy HDL levels is a more practical goal than fixating on any one line of your lipid panel.