Cholesterol is a fatty substance produced in the liver that is necessary for your body to function, with there being both 'good' and 'bad' cholesterol to be found.

It helps the body build cells as well as make vitamins and hormones, but too much of it can also build up in blood vessels which can increase the risk of heart-related problems or strokes.

Cholesterol combines with proteins to be carried around the blood, with this combination known as lipoproteins.

According to NHS Inform, there are two types of lipoprotein called High-density lipoprotein (HDL) and Non-HDL lipoproteins.

HDL carries cholesterol away from the cells and back to the liver to be removed which is why it is referred to as 'good cholesterol'.

Meanwhile, non-HDL is referred to as 'bad cholesterol' because it can build up in blood vessel walls if there’s too much.

What is the range of normal cholesterol people should have?

The target level for your 'good' and 'bad' cholesterol depends on factors like your age, whether you have any health conditions and your risk of cardiovascular disease, the NHS explains.

If you have been ill, are taking some medicines, or have recently had a baby, your levels may be lower or higher.

Healthy adults should have:

  • Below 5mmol/L of total cholesterol in their blood
  • Above 1.0/mmol/L or above 1.2/mmol/L for women of HDL (good cholesterol)
  • Below 4mmol/L of non-HDL (bad cholesterol) 

For clarification mmol/l stands for millimoles per litre. A mole is a scientific unit often used to measure chemicals.

If you have a cholesterol test your GP will use your cholesterol levels along with other factors, such as your age, blood pressure and health conditions, to estimate your risk of cardiovascular disease.

The NHS adds: "They may give you a score (called a QRISK score) which estimates how likely you are to have a heart or circulation problem over the next 10 years."

What are the symptoms of high cholesterol?

LloydsPharmacy Online Doctor Dr Bhavini Shah states that high cholesterol typically shows no symptoms so many people are unaware that their levels are high.

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She continued: "Therefore it is advisable to have regular check-ups and blood tests to monitor cholesterol levels and take steps to manage them if needed.

“If you have concerns about your cholesterol, it's best to discuss them with your GP who can arrange a blood test and suggest any lifestyle changes you can make or if treatment is necessary.”

People can keep their cholesterol levels down by exercising, not smoking and cutting down on foods high in saturated fats, salt and sugar.