Cholesterol Numbers: What Total, LDL, HDL and Triglycerides Mean

In mmol/L:

Cholesterol converts at ÷ 38.67; triglycerides at ÷ 88.57. They are different molecules with different weights, which is why one factor does not cover the panel.

Total cholesterol is the least useful number

It is the sum of the fractions, and the fractions pull in opposite directions.

LDL carries cholesterol toward tissue and is the fraction associated with plaque formation. Lower is better, and it is the number treatment targets.

HDL carries it away and is associated with lower risk. Higher is better.

So a total of 220 mg/dL made of LDL 120 and HDL 75 is a different picture from the same 220 made of LDL 170 and HDL 30 — and total cholesterol cannot distinguish them. That is why a panel reports the parts.

LDL is calculated, not measured, on most panels

Standard panels compute LDL from the other three values using the Friedewald equation rather than measuring it directly.

Two consequences follow. The calculation becomes unreliable when triglycerides are high — above about 400 mg/dL it is not used at all. And because triglycerides rise after eating, a non-fasting sample can distort a calculated LDL.

Newer equations and direct LDL measurement both exist and are used where the calculation is unreliable.

Fasting or not

For years a 9 to 12 hour fast was standard. Current guidance in several countries accepts non-fasting samples for routine screening, because the difference in total and LDL is small and the practical gain in compliance is large.

Triglycerides are the exception — they rise substantially after a meal, so a high non-fasting triglyceride result is usually repeated fasting before being interpreted.

Targets are personal, not universal

The ranges above are general reference points. Treatment targets depend on overall cardiovascular risk, not on the lipid numbers alone — age, blood pressure, smoking, diabetes and family history all enter the calculation, and risk calculators combine them.

Someone with several risk factors may be given an LDL target well below 100 mg/dL. Someone with none may not be treated at a number that would prompt treatment in the first person. A table cannot make that judgment, and this one is not trying to.

What moves the numbers

Diet moves them less than most people expect and exercise moves HDL more than LDL. The largest single lever on LDL for most people is not dietary cholesterol at all but saturated fat intake, since the liver produces the great majority of circulating cholesterol regardless of what arrives in food.

Triglycerides are the fraction most responsive to short-term change — alcohol, refined carbohydrate and weight all move them within weeks, which is also why a single raised triglyceride result is often repeated rather than acted on.

Genetics sets the floor. Familial hypercholesterolaemia is more common than generally assumed and produces LDL levels that lifestyle change cannot bring into range, which is one reason a strong family history belongs in the conversation alongside the numbers.

Non-HDL cholesterol

Total minus HDL. It captures all the cholesterol carried by particles associated with plaque rather than only LDL, and several guidelines now regard it as at least as informative as LDL — particularly when triglycerides are raised.

If it appears on your report, it is not an extra: it is often the more robust of the two.

Unit conversions across the panel run on their own factors, and none is shared with glucose.

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Sources: American Heart Association and American College of Cardiology cholesterol guidance; NIH lipid reference material; NHS High cholesterol.

Reference ranges reproduced for general information. Not medical advice. Interpret any result with the range on your own report and with the clinician who ordered it.