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, or if you are taking (or are about to start) lipid-modifying treatments (e.g. statins).
A blood sample is obtained by inserting a needle into a vein in your arm, or occasionally from a fingerprick.
The guidance on this changed in 2014. Before this, fasting used to be needed for a lipid profile, but is now it is no longer routinely required. However, fasting may still be needed in some circumstances, so you should follow your doctor's advice.
Lipids are a group of fats and fat-like substances that are important constituents of cells and sources of energy. They are necessary for life, but if present in excess they can lead to health problems – in particular cardiovascular disease. A lipid profile measures the level of specific lipids in the blood.
Two types of lipids, cholesterol and triglycerides, are transported in the blood by particles called “lipoproteins”. Each particle contains a combination of protein, cholesterol, triglyceride, and phospholipid molecules. Lipoprotein particles are classified according to their density into high-density lipoproteins (HDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL). Not all of these are measured as part of a routine lipid profile.
A lipid profile typically includes:
- Total cholesterol —this test measures all of the cholesterol in all the lipoprotein particles.
- High-density lipoprotein cholesterol (HDL-C) — measures the cholesterol in HDL particles; often called "good cholesterol" because it removes excess cholesterol and carries it to the liver for removal.
- Non-HDL cholesterol (non-HDL-C) - calculated simply as "total cholesterol minus HDL-C". This is what is often referred to as "bad cholesterol", as unlike "good" HDL-C, it is carried away from the liver and into the walls of blood vessels. Here, it is deposited and begins to form "plaques", which can eventually lead to blockages. Non-HDL-C includes cholesterol carried by LDL, IDL, VLDL, and some also some other particles such as Lp(a) and lipoprotein remnants.
- Triglycerides — measures all the triglycerides in all the lipoprotein particles; most is in the very low-density lipoproteins (VLDL).
Some other information may be reported as part of the lipid profile. These parameters are calculated from the results of the tests identified above.
- Cholesterol: HDL ratio — calculated ratio of total cholesterol to HDL-C.
- Low-density lipoprotein cholesterol (LDL-C) — calculates the cholesterol in LDL particles. LDL-C is a form of "bad cholesterol" - but not all bad cholesterol is LDL-C.
How is the sample collected for testing?
Testing for your lipid profile 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.
Is any test preparation needed to ensure the quality of the sample?
This changed in 2014. Up until then, a 12 hour fast was recommended before having a sample taken for a lipid profile. However, the recommendations have changed, and fasting is no longer routinely needed. However there may be circumstances when fasting is still required, so you should follow instructions given by your doctor.
How is it used?
1) As part of a cardiovascular risk assessment
Cardiovascular disease means disease of the heart, such as a heart attack, or of the arteries, such as strokes. These conditions are partly due to laying down of excess cholesterol in the artery walls (known as atherosclerosis, or “furring up of the arteries”). The balance of different cholesterol fractions measured as part of the lipid profile (e.g. "bad" non-HDL-C vs "good" HDL-C) can influence how fast and extensive this process is. Therefore, the commonest reason to measure a person’s lipid profile is to help estimate their risk of developing cardiovascular disease in the future. This then helps with decisions about lifestyle changes and medical treatments to reduce future risk. In the UK, most doctors use a “risk calculator” (QRISK2) which uses parts of the lipid profile along with other known risk factors (such as age, gender, smoking, blood pressure, diabetes, obesity, and certain chronic illnesses) for this purpose.
2) In cases of pancreatitis
Pancreatitis is a serious medical condition in which the pancreas becomes inflamed. It has many causes, one of which is high levels of triglycerides in the blood. Therefore, if you ever develop pancreatitis, your lipid profile would usually be checked to look for elevated triglycerides. If found, these can be reduced effectively by lifestyle changes and medical treatments.
3) To monitor response to treatment
If you are prescribed lipid-modifying treatments, for example to reduce risk of cardiovascular disease or pancreatitis, your lipid profile may be checked periodically to determine if the treatment is working adequately.
When is it requested?
- In the UK, your lipid profile is commonly tested by your GP when you reach the age of 40, as part of a routine cardiovascular health check.
- It may be checked at other times if you are thought to be at increased risk of cardiovascular disease for another reason.
- It will be checked if you develop another medical condition which can be due to abnormal lipids, such as pancreatitis.
- Finally, it will likely be checked at regular intervals if you have been prescribed lipid-modifying treatments, such as statins.
What does the test result mean?
Is there anything else I should know?
A lipid profile should ideally be measured when a person is healthy. In particular, cholesterol can be temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). To get a true representation of your cholesterol, you should wait at least six weeks after any illness before having it measured. In women, cholesterol and triglyceride conccentrations are high during pregnancy. Women should wait at least six weeks after the baby is born to have a lipid profile measured. Some drugs are known to affect the lipid profile, including oral corticosteroids, beta blockers, oral contraceptives, thiazide diuretics, oral retinoids and phenytoin.
I am used to getting an LDL-C result, but this no longer appears as part of my lipid profile. Why?
For many years LDL-C was used as the main measure of "bad" cholesterol. However it is now recognised that cholesterol carried on other lipoproteins, such as VLDL, Lp(a) and lipoprotein remnants is also harmful. For this reason, the recommendations changed in 2014 so that non-HDL-C should be reported instead of LDL-C. Nevertheless, many people are very used to using LDL-C, including both doctors and patients, so some may continue to use this measure. It should however be recognised that LDL-C cannot accurately be calculated if the lipid profile was taken from someone who wasn't fasting.