Cholesterol is a fatty substance known as a lipid and is vital for the body's normal function. It's mainly made by the liver, but can also be found in some foods.


What is cholesterol?

Cholesterol is a fatty substance found in your blood. If you have too much cholesterol in your blood, it can increase your risk of heart disease, heart attack and stroke. If you have been prescribed statins, your doctor has assessed that you are at significant risk of CVD. Statins can reduce this risk by a third if taken properly and at the right dose.

Cholesterol is carried in your blood by proteins. When the two combine, they're called lipoproteins.

The two main types of lipoprotein are:

  • high-density lipoprotein (HDL) carries cholesterol away from the cells and back to the liver, where it's broken down or passed out of the body as a waste product. For this reason, HDL is referred to as good cholesterol, and higher levels are better.
  • low-density lipoprotein (LDL) carries cholesterol to the cells that need it, but if there's 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 is known as bad cholesterol.

The amount of cholesterol in the blood (both HDL and LDL) can be measured with a blood test.

Why should I lower my cholesterol?

Evidence strongly indicates that high cholesterol can increase the risk of:

  • narrowing of the arteries (atherosclerosis) 
  • heart attack 
  • stroke 
  • transient ischaemic attack (TIA) – often known as a mini stroke
  • peripheral arterial disease (PAD)

This is because cholesterol can build up in the artery wall, restricting blood flow to your heart, brain and the rest of your body. It also increases the risk of a blood clot developing somewhere in your body.

Your risk of developing coronary heart disease also rises as your blood's cholesterol level increases. This can cause pain in your chest or arm during stress or physical activity (angina).

What causes high cholesterol?

Many factors can increase your chances of having heart problems or a stroke if you have high cholesterol.

These include:

  • an unhealthy diet – in particular, eating high levels of saturated fat
  • smoking – a chemical found in cigarettes called acrolein stops HDL transporting cholesterol from fatty deposits 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's also an inherited condition called familial hypercholesterolaemia, which can cause high cholesterol even in someone who eats healthily.

What should my cholesterol levels be?

If you need to have your cholesterol measured, it will be in units called millimoles per litre of blood (mmol/l).

As a general guide, you should aim to have a total cholesterol level of under 4mmol/l - especially if you are at risk of, or already have, heart and circulatory disease.

You should also aim to have your LDL under 2mmol/l and your HDL above 1mmol/l.

However, cholesterol is only one risk factor and the level at which specific treatment is required will depend on whether other risk factors, such as smoking and high blood pressure, are also present.

How can I improve my cholesterol levels?

Lifestyle changes, such as eating a healthy, balanced diet; taking regular exercise and giving up smoking, help to improve cholesterol levels.

Find more information about healthy lifestyles.

You can swap food containing saturated fat with fruit, vegetables and wholegrain cereals. This will also help prevent high cholesterol returning.

But even the strictest low-fat diet can only lower your cholesterol level by up to 10%. This is why it will usually be recommended that you take statins if you are considered to be at high risk of a heart attack or stroke.

But don’t forget, making lifestyle changes will still reduce your risk of developing coronary heart disease.

What are statins and why do they help reduce the risk of heart attacks and strokes?

Statins are a group of medicines that can help lower the level of low-density lipoprotein (LDL) cholesterol in your blood.

LDL cholesterol is often referred to as bad cholesterol, and statins reduce its production inside the liver.

Statins can reduce this risk by a third if taken properly and at the right dose.

Statins are one of the most researched medicines in the world and there is very strong evidence that they help reduce the risk of cardiovascular disease. Statins are most beneficial when you take them on a long-term basis.

Who should take statins?

Having a high level of LDL cholesterol is potentially dangerous, as it can lead to the hardening and narrowing of arteries (atherosclerosis) and cardiovascular disease (CVD) (opens in new window).

You can also be at risk of CVD with what used to be considered normal levels of cholesterol. Statins may be recommended if you have been diagnosed with a form of CVD or have a high risk of developing it in the next 10 years.

Statins can also be used to treat people with a condition called familial hypercholesterolaemia. This is an inherited condition caused by a genetic fault that leads to high cholesterol levels, even in people who have a generally healthy lifestyle.

patients decision aid is available from the National Institute for Health and Care Excellence (NICE) (opens in new window) to help you decide whether you need to take statins to help reduce your risk of having high cholesterol.

When starting a new statin, a routine blood test is advised after three months. You can arrange this with your GP in the usual way. This should demonstrate that your cholesterol level is lower than on your previous treatment.

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