LDL cholesterol: targets, calculation and what lowers it

Cholesterol travels in blood on lipoproteins. LDL stands for low-density lipoprotein, and the cholesterol carried by it is LDL-C. Lab Tests Online UK explains that LDL is considered undesirable because it deposits excess cholesterol in blood vessel walls and contributes to atherosclerosis, the hardening and furring of arteries that ultimately leads to heart disease and strokes.

People who go on to develop cardiovascular disease often have had a high LDL-C for many years before symptoms. That long silent period is why measuring it is useful, and why the NHS stresses that high cholesterol can only be found by a blood test.

LDL-C is commonly tested at the routine cardiovascular health check from age 40, whenever someone is thought to be at increased risk, to monitor treatments such as statins, and when a family history of premature cardiovascular disease raises the possibility of a genetic cholesterol condition. In the UK the first-line lipid value in risk calculators is the total cholesterol to HDL ratio, but LDL-C is almost always checked too and can show, for example, a very high figure suggestive of familial hypercholesterolaemia.

The NHS says you can ask your GP for a cholesterol test if you have not had one and you are over 40, overweight, or have a family history of high cholesterol or heart problems; you can also have a test at a pharmacy, possibly for a fee.

Most laboratories calculate LDL-C from the other parts of the lipid profile. Lab Tests Online UK says strictly speaking fasting is not needed if it is measured directly, and that as long as triglycerides are not significantly raised, non-fasting results can be used for the calculation, so fasting is usually not required, although some tests still ask for a 12-hour water-only fast.

When triglycerides are high the formula becomes unreliable, and a direct LDL-C measurement is used instead; it is almost as accurate as the calculation when triglycerides are normal, which is why direct testing is not the default. Non-HDL cholesterol is also increasingly used, since it accounts for other atherogenic particles.

Elevated LDL-C increases risk, and is combined with age, sex, smoking, blood pressure and weight to estimate the chance of heart disease. If risk is high, LDL-C becomes a target. Lab Tests Online UK says the target for people at high risk is usually no more than 2.0 mmol/L, with a 40 per cent fall from the pre-treatment level as an alternative, and that the lower the LDL-C, the lower the chance of cardiovascular disease.

Treatment starts with diet and lifestyle, and the NHS says you might need medicine if cholesterol has not gone down after changes or if you are at high risk of a heart attack or stroke. Statins reduce the amount of cholesterol your body makes; ezetimibe, bempedoic acid and injections such as alirocumab, evolocumab and inclisiran are used when statins do not work or cannot be taken.

Familial hypercholesterolaemia is an inherited condition that raises LDL-C from birth. Lab Tests Online UK says it affects approximately 1 in 250 people, that early detection can save lives, and that genetic testing is the test of choice, with LDL-C used to pick the most likely affected relative for the first test. The NHS points to HEART UK for information on inherited high cholesterol that starts at a young age.

Low LDL-C is not generally a concern, though it can appear with inherited lipoprotein deficiency, hyperthyroidism, infection and inflammation. LDL-C should be measured when you are well and metabolically stable: illness, surgery, trauma, heart attack, sudden weight change and pregnancy can all temporarily affect it. Call 999 for chest pain or stroke symptoms; do not wait for a cholesterol result.