Blood cholesterol levels are measured with a simple blood test. This blood sample will be used to determine the amount of LDL (bad cholesterol), HDL (good cholesterol) and triglycerides (other fatty substances) in your blood.
You may be asked not to eat for 10-12 hours before the test (usually including when you are asleep at night). This ensures that all food is completely digested and will not affect the outcome of the test.
Your GP or practice nurse can carry out the blood test and will take a blood sample either using a needle and a syringe or by pricking your finger.
Normal cholesterol level
Blood cholesterol is measured in units called millimoles per litre of blood, often shortened to mmol/L.
The government recommends that total cholesterol levels for healthy adults should be 5mmol/L or less, with levels of low-density lipoprotein (LDL) being 3mmol/L or less.
Adults at high risk are defined as those with existing heart disease, high blood pressure (hypertension), diabetes or those with a family history of early heart disease. Those at high risk should have a total cholesterol level of 4mmol/L or less, with levels of LDL being 2mmol/L or less.
In the UK, two out of three adults have a total cholesterol level of 5mmol/L or above. On average, men in England have a cholesterol level of 5.5mmol/L and women have a level of 5.6mmol/L.
The UK population has one of the highest average cholesterol concentrations in the world.
Who should be tested?
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 (for example, if your father or brother developed heart disease or had a heart attack or stroke before the age of 55, or if your mother or sister had these conditions before the age of 65)
- have a close family member who has a cholesterol-related condition, such as familial hypercholesterolaemia (inherited high cholesterol)
- are overweight or obese
- have high blood pressure or diabetes
- have another medical condition such as a kidney condition, an underactive thyroid gland or an inflamed pancreas (pancreatitis). These conditions can cause increased levels of cholesterol or triglycerides.
Assessing your risk
When assessing your risk of heart attack or stroke, your doctor or nurse may refer to your cholesterol ratio. This is your total cholesterol level divided by your level of HDL cholesterol.
Cholesterol levels or cholesterol ratio should not be looked at on their own. Other factors should be taken into consideration when assessing your risk, including:
- your BMI (body mass index), which measures your weight in relation to your height
- treatable risk factors, such as high blood pressure (hypertension), diabetes and other medical conditions
- your age, sex, family history and ethnicity
At the end of your assessment you will be told whether you have a high, moderate or low risk of getting cardiovascular disease (heart disease or stroke) within the next 10 years.
Triglycerides
Your doctor or nurse may also measure your level of triglycerides. Triglycerides are the fats you use for energy and come from the fatty foods you eat. You store what you do not use in the fatty tissues of your body. Excess triglycerides in the blood also increase heart problems.
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