Cholesterol Targets in the UK: What Numbers Mean

The NHS explains that a cholesterol test can measure total cholesterol, HDL cholesterol (the so-called good cholesterol, associated with a lower chance of heart problems or stroke) and non-HDL cholesterol, which is the difference between the total and the HDL. You may only be told your total, but you can ask for the HDL and non-HDL results as well.

Lab Tests Online UK describes the same elements and adds triglycerides, another type of blood fat, and the total to HDL ratio. It notes that non-HDL cholesterol is calculated simply as total cholesterol minus HDL and represents the cholesterol that may be deposited to form plaques. It also explains that reporting changed in 2014 so that non-HDL may be reported instead of LDL.

The reason these numbers matter is not that cholesterol is itself harmful, but that high levels contribute to narrowing of the arteries over years. HEART UK describes cholesterol as a blood fat that plays a vital role in how all our cells work, and says it is when it gets too high that it is a problem.

The NHS publishes guide levels and is careful to say that they are a guide for healthy adults, and that if you have been ill, take some medicines or have recently had a baby your levels may be lower or higher. Lab Tests Online UK lists a slightly longer set.

The NHS is explicit that what is a good target for you depends on age, health conditions and risk of cardiovascular disease. Your GP will use your cholesterol along with age, blood pressure and health conditions to estimate your risk, sometimes giving a QRISK score that estimates how likely you are to have a heart or circulation problem over the next 10 years.

NICE guideline NG238 asks clinicians to measure both total and HDL cholesterol to get the best estimate of risk, and to use clinical findings, a full lipid profile and family history to judge the likelihood of an inherited lipid disorder rather than relying on strict cut-off values alone. It also asks that common secondary causes of high cholesterol, such as excess alcohol, uncontrolled diabetes, hypothyroidism, liver disease and nephrotic syndrome, are excluded before a person is referred for specialist review.

This is why two people with identical cholesterol numbers can be given quite different advice, and why a result just above a guide level is not by itself an instruction to start medication.

Once treatment starts, the target changes from a level to a response. For primary prevention, NG238 says to offer atorvastatin 20 mg to people with a 10-year QRISK3 score of 10 percent or more, and to aim for a greater than 40 percent reduction in non-HDL cholesterol. It also says not to rule out a statin simply because the score is below 10 percent if the person has an informed preference or there is concern that risk is underestimated.

NICE Clinical Knowledge Summaries describes the secondary prevention approach, where people with established cardiovascular disease are offered high-intensity statin treatment regardless of cholesterol level, with a lipid target of LDL cholesterol 2.0 mmol/L or less or non-HDL cholesterol 2.6 mmol/L or less. If the maximum tolerated statin does not reach target after 2 to 3 months, additional treatments may be considered.

NG238 advises arranging specialist assessment for people with a total cholesterol above 9.0 mmol/L or a non-HDL cholesterol above 7.5 mmol/L even without a family history of early heart disease, and urgent specialist review for a triglyceride level above 20 mmol/L not due to alcohol or poor glucose control.

HEART UK explains that familial hypercholesterolaemia is an inherited condition that leads to exceptionally high cholesterol, often double and sometimes four times those of the general population, and that treatment is more effective the sooner it is started. This is the reason an unusually high result in a young person, or a strong family history, is treated differently from a mildly raised result in later life.