Cholesterol Ratio Calculator

The ratios and what each captures

Total cholesterol to HDL ratio divides total cholesterol by HDL. It captures the balance between the fraction associated with risk and the fraction associated with protection.

LDL to HDL ratio is a narrower version using only the two lipoprotein fractions.

Non-HDL cholesterol, total minus HDL, is not a ratio and is increasingly favoured in guidelines. It captures all the atherogenic particles rather than LDL alone, it does not require fasting, and it has performed at least as well as ratios in outcome studies.

Interpreting a ratio

For total cholesterol to HDL, a ratio below about 3.5 is generally considered favourable, around 5 is average, and above 6 is associated with elevated risk.

The ratio can look reassuring for the wrong reason. Someone with a very high HDL and a high LDL may have an acceptable ratio while carrying substantial atherogenic particle burden, and someone with a low LDL and a low HDL may have a poor ratio with lower actual risk.

Which is why the individual values matter alongside the ratio, and why modern guidelines have shifted towards LDL and non-HDL targets rather than ratios for treatment decisions.

The HDL story, and how it changed

HDL was described for decades as good cholesterol on the basis of consistent observational data linking higher levels to lower cardiovascular risk.

That interpretation has been substantially revised. Drugs that raise HDL have repeatedly failed to reduce cardiovascular events in trials, and Mendelian randomisation studies have not supported a causal protective role for HDL levels.

Very high HDL, above roughly 2.3 millimoles per litre, has been associated with increased mortality in several large cohorts, which does not fit the simple protective model at all. The current understanding is that HDL function matters more than HDL concentration, and that concentration is a marker rather than a lever.

What actually drives treatment decisions

UK guidance uses QRISK3 to estimate ten year cardiovascular risk, incorporating age, sex, ethnicity, blood pressure, cholesterol ratio, smoking, diabetes, family history and several conditions.

Treatment is offered on the basis of that overall risk rather than on any single lipid value, which is why two people with identical cholesterol can receive different advice.

For people already on treatment, or with familial hypercholesterolaemia, or with established cardiovascular disease, the targets differ again. None of this is derivable from a ratio, which is a single input among many.

What changes the numbers

Dietary saturated fat raises LDL, and replacing it with unsaturated fat lowers it. That is one of the better-established relationships in nutrition, and the effect size for an individual varies considerably.

Soluble fibre, particularly from oats and psyllium, lowers LDL modestly. Plant stanols and sterols do too. Weight loss and exercise raise HDL and lower triglycerides.

Statins lower LDL substantially and have strong outcome evidence in appropriate populations. The decision to take one belongs with a doctor working from an overall risk assessment, and it is a decision that a cholesterol ratio informs rather than determines.

One practical point about the blood test itself. Fasting was standard for lipid panels for decades and is no longer required in most guidelines, including in the UK, because non-fasting samples predict outcomes at least as well. Triglycerides are the fraction most affected by a recent meal, and where a fasting sample is specifically wanted it is usually because triglycerides are the concern. If a laboratory or a clinician asks for fasting, follow that instruction; if nobody has, a non-fasting sample is generally fine.