The lipid panel, line by line

A standard lipid panel looks like six numbers. In most US labs, three are measured directly (total cholesterol, HDL cholesterol and triglycerides) and the rest are arithmetic on those three. Knowing which is which explains why LDL can jump when nothing changed but a meal, and why some clinicians prefer markers that are not on the standard panel at all.

What is on the report

Quest's consumer lipid panel, for example, lists LDL, the ratio and non-HDL as calculated. Some labs measure LDL directly, which the report will say.

Three ways to calculate LDL

Friedewald (1972). LDL equals total cholesterol minus HDL minus triglycerides divided by five (in mg/dL). The divide-by-five assumes a fixed ratio of triglycerides to VLDL cholesterol. It is unreliable when triglycerides are 400 mg/dL or more, and it underestimates LDL when LDL is low and triglycerides are moderately high.

Martin/Hopkins (2013). Using 1,350,908 US lipid profiles in JAMA, Martin and colleagues replaced the fixed factor with one drawn from a 180-cell table based on triglycerides and non-HDL. In samples with triglycerides of 200 to 399 mg/dL and an estimated LDL under 70 mg/dL, directly measured LDL was also under 70 in 84.0 percent with the new method against 40.3 percent with Friedewald.

Sampson/NIH (2020). Developed at the National Institutes of Health against the ultracentrifugation reference method and published in JAMA Cardiology, it calculates LDL accurately with triglycerides up to 800 mg/dL, about as well as Friedewald does below 400.

The practical point: a lab switching equations can move your LDL without any change in you. If LDL changes between two reports, check whether the method line changed. The lab report guide explains why a change of lab is a break in the series.

The cut-points

The categories most US reports still use come from the 2002 NCEP ATP III report. Treatment decisions under the 2018 ACC/AHA guideline depend on overall risk, not on these categories alone.

The 2018 ACC/AHA guideline adds two thresholds that change management directly: LDL of 190 mg/dL or more, which on its own calls for statin therapy without a risk calculation, and persistent triglycerides of 175 mg/dL or more, fasting or not, which count as a risk-enhancing factor.

Fasting is mostly optional now

A 2016 joint consensus from the European Atherosclerosis Society and the European Federation of Clinical Chemistry and Laboratory Medicine concluded that fasting is not routinely required. After ordinary meals, the maximal mean change was about plus 26 mg/dL for triglycerides and minus 8 mg/dL for LDL, which they judged not clinically significant. The 2018 ACC/AHA guideline accepts fasting or non-fasting profiles for adults not on lipid-lowering drugs, and recommends repeating fasting if a non-fasting triglyceride result is 400 mg/dL or more. A 2024 Clinical Chemistry review reported that guidelines in Europe, the US, Canada, Brazil, Japan, India and Australia now endorse non-fasting profiles in some or all patients. Many US labs still print fasting instructions; the fasting guide covers when it still matters.

What the standard panel leaves out

ApoB counts atherogenic particles directly, one ApoB molecule per particle, rather than estimating the cholesterol inside them. It and LDL usually agree; they diverge with high triglycerides, diabetes and obesity. Lp(a) is largely inherited, and the 2022 European Atherosclerosis Society statement recommends measuring it once in every adult. Neither is on a standard panel. The longevity bloodwork page covers both against the guideline numbers.

What moves a lipid panel

• Triglycerides move most: with the last meal, alcohol in the previous days, weight change and blood sugar control.
• LDL moves with saturated fat intake, weight, thyroid function and medicines, and can shift with the calculation method.
• HDL moves slowly, upward with exercise and weight loss and downward with smoking.
• Acute illness lowers total and LDL cholesterol temporarily, so a panel drawn during or just after an infection can look better than usual.

On a GLP-1, triglycerides fall the most; in STEP 1 they fell 21.9 percent on semaglutide against 7.3 percent on placebo. The GLP-1 blood work page has the full table.

How often

The CDC says most healthy adults should be tested every 4 to 6 years, more often with heart disease, diabetes or a family history. After starting or changing a statin, the 2018 ACC/AHA guideline recommends a repeat lipid measurement 4 to 12 weeks later and then every 3 to 12 months as needed. See how often to get blood work.

In the app

Peptide AI reads total cholesterol, LDL, HDL and triglycerides into its metabolic panel and plots each against your dose timeline and nutrition log, which is where a triglyceride swing usually finds its explanation. See bloodwork tracking.