Cholesterol levels explained: total, LDL, HDL and triglycerides.

Cholesterol is often discussed as if it were a single thing to be minimised. In reality, a cholesterol result is a panel of four or five distinct measurements, each with a different relationship to cardiovascular risk. Understanding what each number means, and how they relate to each other, gives you a much clearer picture of your heart health.

The four key measurements.

Your lipid panel at a glance

Marker	What it is	UK target
Total cholesterol	All cholesterol in the blood combined.	Below 5.0 mmol/L, ideally
LDL	The "bad" cholesterol that deposits in artery walls.	Below 3.0 mmol/L; below 2.0 if high risk
HDL	The "good" cholesterol that removes LDL from arteries.	Above 1.0 mmol/L for men, 1.2 for women
Triglycerides	Blood fats linked to diet and insulin resistance.	Below 1.7 mmol/L, fasting
Non HDL	Total minus HDL: every potentially harmful particle.	Below 4.0 mmol/L

Why total cholesterol alone is misleading.

A total cholesterol of 6.0 mmol/L could represent very different cardiovascular risk depending on the composition. If that 6.0 is made up of 1.8 mmol/L LDL and 3.2 mmol/L HDL, the risk profile is very different from 4.5 mmol/L LDL and 0.9 mmol/L HDL, even though the total is the same.

This is why the total cholesterol to HDL ratio is a more useful single number than total cholesterol alone. The NHS uses this ratio as part of cardiovascular risk calculators such as QRISK3.

LDL cholesterol: the primary target.

LDL, low density lipoprotein, is the primary driver of atherosclerosis: the build up of plaques in artery walls that underlies most heart attacks and strokes. The lower your LDL, the lower your risk, with no clear lower threshold below which further reduction stops being beneficial.

The NHS targets for LDL depend on your overall cardiovascular risk:

• Low risk, a ten year cardiovascular risk below 10%: below 3.0 mmol/L.
• High risk, a ten year risk above 10% or established cardiovascular disease: below 2.0 mmol/L, or a 50% reduction from baseline.
• Very high risk, a previous heart attack, stroke, or diabetes with complications: below 1.8 mmol/L.

HDL cholesterol: the protective factor.

HDL, high density lipoprotein, removes cholesterol from artery walls and transports it back to the liver for disposal. Higher HDL is generally protective. Low HDL, below 1.0 mmol/L in men or 1.2 mmol/L in women, is an independent risk factor for cardiovascular disease.

HDL is raised by regular aerobic exercise and stopping smoking. It is lowered by sedentary behaviour, obesity, and a diet high in refined carbohydrates.

Triglycerides: the dietary marker.

Triglycerides are blood fats that reflect recent dietary intake and metabolic health. They are strongly influenced by carbohydrate and alcohol consumption, and elevated triglycerides are closely associated with insulin resistance. A fasting triglyceride above 1.7 mmol/L is considered elevated. Above 5.6 mmol/L carries a risk of pancreatitis.

Non HDL cholesterol.

Non HDL cholesterol, total cholesterol minus HDL, captures all the potentially harmful particles in the blood, including LDL, VLDL and IDL. It is increasingly used as a primary target because it does not require fasting and may be a better predictor of risk than LDL alone. The NHS target is below 4.0 mmol/L.

What to ask your GP.

• What is my total cholesterol to HDL ratio, and what does it mean for my risk?
• What is my ten year cardiovascular risk score, QRISK3?
• Should I be aiming for a lower LDL target given my risk factors?
• How do my triglycerides compare to my previous tests?
• Are lifestyle changes sufficient, or should we discuss medication?