A lipid panel is a blood test that measures four types of fats in your blood: total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. Together, these numbers give a snapshot of your cardiovascular risk and help determine whether the fats circulating in your bloodstream are at levels that could damage your arteries over time.
The Four Core Measurements
Every standard lipid panel reports the same four values. Each one tells a different part of the story.
Total cholesterol is the sum of all the cholesterol in your blood. It’s a useful starting point, but on its own it doesn’t reveal much. A total cholesterol of 210 mg/dL could mean very different things depending on how that number breaks down between the good and bad types.
LDL cholesterol is often called “bad” cholesterol because it’s the primary driver of plaque buildup in your arteries. When LDL particles enter your artery walls, they trigger a chain of inflammation, attract immune cells, and gradually form hardened deposits that narrow the arteries. This process, atherosclerosis, is what leads to heart attacks and strokes. LDL is the number most treatment decisions are based on.
HDL cholesterol works in the opposite direction. It acts like a cleanup crew, pulling excess cholesterol out of your artery walls and ferrying it back to your liver, where it’s either recycled or eliminated through bile. This process is why HDL is labeled “good” cholesterol. Higher levels are generally protective.
Triglycerides are a different type of fat entirely. Your body converts excess calories, especially from sugar and alcohol, into triglycerides and stores them for energy. Some triglycerides in your blood are normal and necessary, but elevated levels contribute to atherosclerosis in their own way. When triglycerides are broken down, they leave behind remnant particles containing leftover cholesterol and fatty acids. These remnants trigger inflammation in artery walls and accelerate plaque buildup. A triglyceride level over 200 mg/dL raises your risk of dying from cardiovascular disease by about 25% compared to someone with normal levels.
What the Numbers Mean for Adults
Current guidelines don’t use a single “good or bad” cutoff for adults the way they once did. Instead, your results are interpreted in the context of your overall cardiovascular risk, including factors like age, blood pressure, diabetes, and smoking status. That said, certain thresholds are widely used as reference points.
For LDL cholesterol, most adults fall somewhere between 70 and 189 mg/dL. An LDL of 190 mg/dL or higher is classified as severe hypercholesterolemia and typically calls for treatment regardless of other risk factors. For people who already have heart disease, the target is often well below 70 mg/dL.
For triglycerides, below 150 mg/dL is the standard goal, but below 100 mg/dL is considered ideal for reducing heart disease risk. Levels of 500 mg/dL or above are classified as severe hypertriglyceridemia and carry additional risks, including inflammation of the pancreas.
For HDL, higher is better. There’s no upper limit to worry about for most people, but low HDL (typically below 40 mg/dL for men or below 50 mg/dL for women) is considered a risk factor on its own.
Non-HDL Cholesterol: The Fifth Number
Many labs now report a fifth value called non-HDL cholesterol. It’s simply your total cholesterol minus your HDL. This number captures all the cholesterol-carrying particles that can contribute to plaque, not just LDL but also other harmful types like VLDL.
Many clinicians now consider non-HDL cholesterol a better predictor of heart disease risk than LDL alone, because it accounts for a broader range of dangerous particles. An optimal non-HDL level for most adults is less than 130 mg/dL. If you have a history of heart attack, the target is typically lower.
How LDL Is Calculated (and When It’s Wrong)
Here’s something most people don’t realize: LDL cholesterol usually isn’t measured directly. It’s calculated using a formula developed in 1972 that plugs in your total cholesterol, HDL, and triglycerides. The formula assumes a fixed ratio between triglycerides and another lipoprotein called VLDL.
This works well for most people, but the calculation starts losing accuracy when triglycerides are above 150 mg/dL and becomes unreliable above about 400 mg/dL. It also tends to underestimate LDL in people whose LDL is already very low (below 70 mg/dL). If your triglycerides are elevated, your doctor may order a direct LDL measurement instead of relying on the calculated value.
Do You Need to Fast?
The traditional advice was to fast for 9 to 12 hours before a lipid panel, but guidelines have shifted. Major medical organizations, including the American College of Cardiology, the American Heart Association, and the Canadian Cardiovascular Society, now consider a non-fasting test equally acceptable for routine screening. Total cholesterol and HDL barely change after a meal. Triglycerides do rise after eating, so if your non-fasting triglycerides come back elevated, your doctor may ask for a follow-up fasting test to confirm. If you’re already known to have high triglycerides, fasting before the draw still makes sense.
What Each Result Tells You About Risk
No single number on a lipid panel works in isolation. A person with an LDL of 140 mg/dL and an HDL of 75 mg/dL is in a very different situation than someone with the same LDL but an HDL of 35 mg/dL. The combination matters.
That said, LDL is the value most directly tied to treatment decisions. Atherosclerosis is fundamentally a disease driven by LDL particles accumulating in artery walls. Lowering LDL reduces the amount of cholesterol available to form new plaque and can even stabilize existing deposits. This is why, for people at high cardiovascular risk, aggressive LDL reduction is the primary goal.
Triglycerides add an independent layer of risk. Even when LDL is well controlled, persistently elevated triglycerides above 150 mg/dL signal ongoing metabolic stress and continued arterial inflammation from those remnant particles. Elevated triglycerides also tend to travel with other problems: insulin resistance, excess abdominal fat, and low HDL. When all of these appear together, the combination is sometimes called metabolic syndrome, and it significantly raises cardiovascular risk beyond what any single number would suggest.
HDL, while protective, is the hardest number to move with medication. Lifestyle changes like regular aerobic exercise, moderate alcohol intake, and not smoking tend to raise it modestly. Its value on a lipid panel is primarily as a risk modifier: low HDL makes an otherwise borderline profile more concerning, while high HDL provides some reassurance.
How Often to Get Tested
For adults with no known risk factors, a lipid panel every four to six years is a common recommendation starting at age 20. If you have risk factors like diabetes, high blood pressure, obesity, a family history of early heart disease, or you’re already taking cholesterol-lowering medication, more frequent testing (typically every one to two years) helps track whether your levels are moving in the right direction. Children and adolescents are generally screened at least once between ages 9 and 11, using slightly different reference ranges. For children, an LDL below 110 mg/dL and triglycerides below 75 mg/dL (under age 10) or below 90 mg/dL (ages 10 to 19) are considered acceptable.