HDL Cholesterol Test
Aged 40 as part of a routine cardiovascular health check, or if you are already thought to be at risk of cardiovascular disease for another reason (including already having suffered from cardiovascular disease).
Testing for HDL cholesterol requires a blood sample. Most often, the blood sample is collected by venepuncture (using a needle to collect blood from a vein in the arm). Occasionally a fingerprick test can be used, although this is not commonly available in GP practices or hospitals in the UK.
No fasting is needed for an HDL-cholesterol test, or the full lipid profile. On the other hand, there may be circumstances when fasting is still required, so you should follow the instructions given by your health care team.
HDL is one of the classes of lipoproteins that carry cholesterol in the blood. HDL is thought to be beneficial because it removes excess cholesterol from tissues and carries it to the liver for disposal. Hence HDL cholesterol is often called “good” cholesterol. However although low HDL levels are associated with increasing cardiovascular risk high levels are not necessarily protective. The test for HDL measures the amount of cholesterol carried on HDL particles in blood.
How is it used?
HDL-cholesterol testing is usually used to help find out your risk of developing cardiovascular disease. If you have a high cholesterol, your doctor may wish to know how much is non-HDL cholesterol or HDL-cholesterol.
Your HDL-cholesterol can be used, along with total cholesterol and other factors, in "risk calculators" such as QRISK2, which estimate your future risk of getting cardiovascular disease. The value which is entered into the calculator is actually the "total cholesterol to HDL-C ratio", ie the balance between total cholesterol and HDL cholesterol. Knowing your future risk can guide decisions on making lifestyle changes or starting medical treatments.
When is it requested?
HDL is usually requested with other tests, either with cholesterol or as part of a lipid profile, including non-HDL and triglycerides. This is done during a routine cardiovascular risk assessment, which GPs offer to people aged 40 or over. If your doctor thinks you could be at higher risk of cardiovascular disease for another reason, they may recommend HDL testing at other times. It is fairly standard as part of yearly checks in people who have established cardiovascular disease e.g. previous stroke or heart attack.
What does the test result mean?
Low levels of HDL cholesterol are worse than normal HDL cholesterol. The lower your HDL cholesterol level, the higher risk of developing cardiovascular disease. This is because low HDL infers that the LDL particles are smaller and denser than normal which makes them more atherogenic (likely to cause atherosclerotic plaque/furring of the arteries). Having higher than normal HDL is unlikely to have any protective effects in most people.
Other factors can affect your HDL cholesterol result. For example, physical exercise and moderate alcohol consumption increase your HDL cholesterol, whereas smoking reduces it.
Is there anything else I should know?
HDL cholesterol should not be measured when a person is suddenly unwell. Cholesterol is temporarily low during sudden illness, immediately following a heart attack, or during stress (like from surgery or an accident). You should wait at least 6 weeks after any illness to have cholesterol measured. In women, HDL cholesterol may change during pregnancy. You should wait at least six weeks after your baby is born to have your HDL-cholesterol measured.
My HDL is high. Is this a problem?
This is uncertain. If the cause is due to problem drinking for example then there are no health benefits. There are families who have high HDL (hyperalphalipoproteinaemia) and some of those families have less cardiovascular disease and some more. This may be due to whether the particles work properly but HDL metabolism is incompletely understood. We are increasingly sure however that when HDL is normal any further increases in concentration bring about no further benefit.