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) treatments which lower cholesterol.
A blood sample taken from a vein in the arm, or occasionally a fingerprick
No fasting is needed for a cholesterol test. However, you should follow your doctor's advice as fasting might be needed for other tests being performed.
Cholesterol is a substance that is essential for life. It helps form the membranes for cells in all organs and tissues in your body. It is used to make hormones that are essential for development, growth and reproduction. It forms bile acids that are needed to absorb nutrients from food. Cholesterol comes both from what you eat and from your body's own production of cholesterol, which takes place in the liver.
A small amount of your body’s cholesterol circulates in the blood in complex particles called "lipoproteins". These include some particles that carry excess cholesterol away for disposal (see HDL, good cholesterol) and some particles that deposit cholesterol in tissues and organs (see non-HDL, bad cholesterol). The test for cholesterol measures all cholesterol (good and bad) that is carried in the blood. However, when you have a cholesterol test, your doctor would usually be looking to see if it is high, which most commonly is due to having too much bad non-HDL cholesterol.
How is the sample collected for testing?
Testing for 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.
Is any test preparation needed to ensure the quality of the sample?
No fasting is needed for a cholesterol test. In the past, a full lipid profile (which includes cholesterol) did require fasting, but this changed in 2014, and even the full lipid profile no longer requires fasting. On the other hand, there may be circumstances when fasting is still required, so you should follow instructions given by your doctor.
How is it used?
Cholesterol is different from most tests in that it is not always used to diagnose or monitor a disease but is used to estimate the risk of developing a disease, specifically cardiovascular disease. Cardiovascular disease includes heart disease (angina, heart attacks), stroke, and peripheral vascular disease (causing blocked circulation in the legs). It is due to hardening or "furring" up of the arteries (atherosclerosis), which is more likely to happen when you have a high cholesterol level. For this reason, checking your cholesterol can tell you and your doctor if you are at risk of heart disease, before you actually develop it, so you can do something about it.
To estimate your risk of cardiovascular disease, your doctor can use your cholesterol result, along with other information, into a risk calculator such as QRISK2. The value which is used in the calculator is actually your total cholesterol to HDL-C ratio, ie the balance between total cholesterol and good cholesterol.
When is it requested?
Cholesterol 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, as if this is the case, it is even more important to keep your cholesterol under control. Risk factors for cardiovascular disease include:
- Family history. History of high cholesterol or heart disease in close relatives particularly if occurring before age 55 in women or 65 in men. If the family history is not known, a cholesterol test is recommended, especially if other risk factors are present.
- Being overweight or obese.
- Consuming excessive amounts of cholesterol and saturated fats
- Diabetes mellitus
- High blood pressure (hypertension)
- Smoking cigarettes
Finally, it will likely be checked at regular intervals if you have been prescribed treatments to help lower your cholesterol, such as statins.
What does the test result mean?
There is no set number which defines "normal" or "abnormal" for cholesterol. A large number of studies have shown that as your cholesterol decreases, your risk of cardiovascular disease also decreases, and in fact, there is no point where this levels off. In other words, the lower your cholesterol, the better. In the past, a total cholesterol value of less than 5.0 mmol/L was often used as a reasonable "healthy" level for most people. On the other hand, a value of less than 4.0 mmol/L was used if the person was already considered to be at higher risk of cardiovascular disease. It is likely that many people will continue using similar "targets", and indeed it is convenient to do so - but it is still worth bearing in mind that most important point is that lower the cholesterol, the better.
Is there anything else I should know?
There is condition which runs in families called “familial hypercholesterolaemia” in which cholesterol is very high – usually over 7.5 mmol/L in adults. In fact, it is the LDL cholesterol specifically which is high. Some people, though not all, who have a cholesterol result this high, have familial hypercholesterolaemia. This is an inherited condition which is important to pick up, as if it isn’t treated there is a high risk of heart disease at a young age. Furthermore, as it is inherited, other family members might be affected. Anyone suspected of having familial hypercholesterolaemia should be referred to a specialist lipid clinic.
Cholesterol should ideally be measured when a person is healthy. It is 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 is high during pregnancy. Women should wait at least six weeks after the baby is born to have cholesterol measured.
Some drugs that are known to increase cholesterol levels include oral corticosteroids, beta blockers, oral contraceptives, thiazide diuretics, oral retinoids and phenytoin.
There has historically been some debate about whether a very low cholesterol level is harmful. Low cholesterol is often seen when there is an existing problem like malnutrition, liver disease, or cancer. However there is no evidence that low cholesterol causes any of these problems.
What causes high cholesterol?
High cholesterol may be the result of an inherited disease or it may result from a diet high in saturated fats. For many people it is caused by a combination of both a high fat diet and an inherited tendency towards high cholesterol. In most cases where the cholesterol is high, it is mainly due to having a high non-HDL (bad) cholesterol, although occasionally it can be due to a high HDL cholesterol, which is not thought to be harmful. This is why is usually helpful to have a full lipid profile checked.
What treatments are recommended if my levels are too high?
The first step in treating high cholesterol, usually due to a high non-HDL cholesterol, is adoption of a healthy diet. In particular, people are often advised to reduce saturated fat intake, and increase intake of foods which are known to lower non-HDL cholesterol, including vegetables, oats, soya, nuts, and some spreads fortified with ‘plant stanols’ or ‘plant sterols’. For advice on how to lower cholesterol through diet and lifestyle, visit the Heart UK website. If dietary changes alone do not adequately lower cholesterol, drugs may be prescribed. A class of drug called ‘statins’ is usually used first line. Statins have been around for many years and there is excellent evidence that they are effective in lowering LDL cholesterol and other forms of bad cholesterol, and have a low rate of side effects. Other drugs that are available include ezetimibe, bile acid sequestrants and fibrates. These are usually used second or third line if statins are not sufficient.
What is my risk of a heart attack if I have high cholesterol?
High cholesterol increases your risk of a heart attack. The higher the cholesterol, the higher the risk. However, many other factors also affect your risk of a heart attack, such as smoking, diabetes, age, and high blood pressure. Charts are available which enable the risk to be estimated for individuals.Your doctor can use charts and equations which use several factors to estimate your future risk of developing cardiovascular disease.
I haven't changed my diet or exercise pattern but my cholesterol has gone up since the last time it was tested. Why?
Cholesterol levels fluctuate over time. The measured cholesterol level may differ by as much as 10% from one month to another. It may go up sometimes or it may go down sometimes. These changes are called biological variation and they represent normal variability inherent in human metabolism. Cholesterol levels also tend to climb a little with age.
My doctor told me I had a high cholesterol test but instead of treating me he told me to wait a few months and test it again. Why?
Cholesterol levels fluctuate over time. A single measurement of cholesterol may not always reflect the "usual” cholesterol level. For this reason, it is advisable to have at least two different measurements several weeks to several months apart before beginning any kind of treatment. Treatment is based on the average value. It may also allow an opportunity to determine whether dietary intervention has any impact on the cholesterol level, prior to considering drug therapy.