A cholesterol test is a simple blood test that can be performed by your doctor or pharmacist, or can be bought over the counter for you to do at home.
A cholesterol test can tell you if your cholesterol level is higher than it should be, so that you can take steps to lower it. High cholesterol levels themselves do not cause symptoms, but over time can lead to cardiovascular disease, so it is useful to have a cholesterol test if you think you may be at risk.
What is cholesterol?
Cholesterol is a fatty substance that is made by the liver from the fats in the foods we eat. It is carried in the circulation by lipoproteins. Cholesterol that is carried by low-density lipoproteins (LDL cholesterol) is commonly known as ‘bad’ cholesterol. This increases cardiovascular disease risk. Cholesterol associated with high-density lipoproteins (HDL cholesterol) is known as ‘good’ cholesterol, which is believed to have a protective effect against cardiovascular disease.
Why might I need a cholesterol test?
In general, high cholesterol is due to too much fat in the diet and most of our diets put us at risk of high cholesterol. However, two people with the same diet can have very different cholesterol levels and it isn’t possible to tell just by looking at them. Only a cholesterol test can provide accurate information on cholesterol levels.
You might also need a cholesterol test if you have underlying health conditions such as an underactive thyroid gland, obesity, alcohol problems and some kidney and liver disorders. These can all cause elevated cholesterol. In rare cases, familial hypercholesterolaemia a hereditary condition can lead to very high cholesterol that runs in families. It is caused by a genetic defect that affects the way that cholesterol is produced by the liver and can be diagnosed by cholesterol tests combined with genetic tests.
When are cholesterol tests recommended?
Anyone can request a cholesterol test from their doctor, or you can take a basic cholesterol test at a pharmacy or at home. For some people, cholesterol tests are recommended because they have several risk factors for cardiovascular disease. Cholesterol tests are done routinely as part of a cardiovascular risk assessment in:
- All adults aged over 40
- Adults of any age who have:
- A strong family history of early cardiovascular disease (a father or brother who developed heart disease or a stroke before they were 55, or a mother or sister who experienced a cardiovascular event before they were 65)
- A first degree relative (parent, brother, sister, child) with a serious hereditary lipid disorder such as familial hypercholesterolaemia
- Even if you don’t fall into one of the categories above, you may wish to take a cholesterol test if you have other risk factors, including:
- Lifestyle factors
- An inactive lifestyle
- High blood pressure
- Diminished kidney function
- Gender (men are at increased risk of cardiovascular disease)
- Ethnic background (people with recent ancestry in India, Pakistan, Bangladesh, or Sri Lanka are at increased risk)
What information will I get from a cholesterol test?
A basic cholesterol test consists of a finger prick test and can performed at a pharmacy or at home. These cholesterol tests will indicate your total cholesterol (TC) level. If this is found to be high, it is important to visit your doctor for more detailed cholesterol tests, which tell you your TC level, individual levels of LDL and HDL cholesterol, and your TC/HDL ratio. This ratio is an important part of your cholesterol test results, as it reflects how much of your total cholesterol level is made up of bad and good cholesterol. As good cholesterol is believed to have a protective effect, you should have more HDL than LDL cholesterol.
Ideal results of a cholesterols test are:
- TC: 5.0 mmol/l or less
- LDL cholesterol: 3.0 mmol/l or less
- HDL cholesterol: 1.2 mmol/l or more
- TC/HDL ratio: 4.5 or less
What are the complications of high cholesterol?
High levels of LDL (bad) cholesterol in the blood over a long period of time can lead to the formation of fatty deposits or ‘plaques’ called atheroma on the blood vessel walls. Over time, these plaques can accumulate and become larger, causing narrowing and hardening of the arteries, leading to cardiovascular disorders such as angina, heart attacks or stroke.
Unfortunately, high cholesterol has no symptoms until cardiovascular disease is present. If you think you may be at risk of high cholesterol levels, ask your doctor about cholesterol tests, as early diagnosis can reduce your risk of developing cardiovascular disease.
What if my cholesterol test shows my levels are too high?
Even if your cholesterol test shows that your levels are too high, you can reduce them along with your risk of cardiovascular disease by making changes to your lifestyle and, if necessary, taking medication. Changing your diet to reduce the amount of fat you eat can help to lower your cholesterol levels, while statins are often used to control cholesterol levels and correct the TC/HDL ratio.
Profile of the author
Dr Kathryn Senior is an acclaimed medical journalist who has written over 500 feature articles for leading international journals within The Lancet group