Cholesterol is a fatty substance known as a lipid and is vital for the normal functioning of the body. It is mainly made by the liver but can also be found in some foods we eat.
Having an excessively high level of lipids in your blood (hyperlipidemia) can have an effect on your health. High cholesterol itself does not cause any symptoms, but it increases your risk of serious health conditions.
Cholesterol is carried in your blood by proteins, and when the two combine they are called lipoproteins. There are harmful and protective lipoproteins known as LDL and HDL, or bad and good cholesterol.
Low-density lipoprotein (LDL): LDL carries cholesterol from your liver to the cells that need it. If there is too much cholesterol for the cells to use, it can build up in the artery walls, leading to disease of the arteries. For this reason, LDL cholesterol is known as "bad cholesterol".
High-density lipoprotein (HDL): HDL carries cholesterol away from the cells and back to the liver, where it is either broken down or passed out of the body as a waste product. For this reason, it is referred to as "good cholesterol" and higher levels are better.
The amount of cholesterol in the blood (both LDL and HDL) can be measured with a blood test. The recommended cholesterol levels in the blood vary between healthy adults and those at higher risk.
Why should I lower my cholesterol?
Evidence strongly indicates that high cholesterol can increase the risk of:
This is because cholesterol can build up in the artery wall, restricting the flow of blood to your heart, brain and the rest of your body. It also increases the chance of a blood clot developing somewhere.
Your risk of coronary heart disease (when your heart's blood supply is blocked or disrupted) also rises as your blood's cholesterol level increases and this can cause angina during physical activity.
What causes high cholesterol?
There are many factors that can increase your chance of having heart problems or stroke if you have high cholesterol, including the following:
- an unhealthy diet: some foods already contain cholesterol (known as dietary cholesterol) but it is the amount of saturated fat in your diet which is more important
smoking: a chemical found in cigarettes called acrolein stops HDL from transporting LDL to the liver, leading to narrowing of the arteries (atherosclerosis)
- having diabetes or high blood pressure (hypertension)
- having a family history of stroke or heart disease
There is also an inherited condition known as familial hypercholesterolaemia (FH). This can cause high cholesterol even in someone who eats healthily.
Read more about the causes of high cholesterol.
When should I test my cholesterol levels?
Your GP may recommend that you have your blood cholesterol levels tested if you:
- have been diagnosed with coronary heart disease, stroke or mini-stroke (TIA) or peripheral arterial disease (PAD)
- are over 40
- have a family history of early cardiovascular disease
- have a close family member has a cholesterol-related condition
- are overweight
- have high blood pressure, diabetes or a health condition that can increase cholesterol levels, such as an underactive thyroid
Read more about how high cholesterol is tested.
How can I lower my cholesterol levels?
The first step in reducing cholesterol is to maintain a healthy, balanced diet. It is important to keep your diet low in fatty food, especially food containing saturated fat, and eat lots of fruit, vegetables and wholegrain cereals. This will also help to prevent high cholesterol from returning.
Other lifestyle changes can also make a big difference. It will help to lower your cholesterol if you do regular exercise and quit smoking. Read more information about how to stop smoking and tips on improving your health and fitness.
If these measures are not helping to reduce your cholesterol and you continue to be at a high risk of heart disease, your GP may prescribe a cholesterol-lowering medication such as statins. Your GP will take into account the risk of any side effects from statins and the benefit of lowering your cholesterol must outweigh any risks.
Read more about how high cholesterol is treated.