Blood cholesterol tests determine the amount of LDL (Low Density Lipoprotein) ‘bad’ cholesterol, HDL (High Density Lipoprotein) ‘good’ cholesterol) and triglycerides (other fatty substances) in your blood.

They are designed to assess whether you have a high, moderate or low risk of getting cardiovascular disease (heart disease or stroke) within the next 10 years.

However, the risk assessment is not just based on your cholesterol reading. It also takes into account:

• your BMI (body mass index), a measure of your weight in relation to your height

• other medical factors, including high blood pressure (hypertension) and diabetes

• your age, sex, family history and ethnicity

Blood cholesterol is measured in millimoles per litre of blood, shortened to mmol/L.

Recommended cholesterol levels

TOTAL CHOLESTEROL
The official recommendation is that total cholesterol should be:

• 5 mmol/L or less for healthy adults
• 4 mmol/L or less for those at high risk

On average, men in England have a cholesterol level of 5.5 mmol/L and women have a level of 5.6 mmol/L. Over 60% of adults have a cholesterol level above 5 mmol/L.

LDL ‘BAD’ CHOLESTEROL
This is not the whole risk story by any means. Firstly, total cholesterol is not a good marker of potential trouble. LDL is the ‘bad’ cholesterol and levels of LDL should be:

• 3 mmol/L of LDL or less for healthy adults
• 2 mmol/L of LDL or less for those at high risk

HDL ‘GOOD’ CHOLESTEROL
HDL is the ‘good’ form and should be above 1 mmol/L. A lower level of HDL than this can increase your risk of heart disease.

Your doctor may also calculate your total cholesterol level divided by your HDL level. Generally, this total to HDL ratio should be below 4, as a higher ratio increases heart disease risk.

TRIGLYCERIDES
These are the fats you use for energy and come from the fatty foods you eat. Excess triglycerides in the blood increase heart problems.

Your ideal level of triglycerides should be less than 1.7 mmol/L.

Higher-risk individuals
It’s a really good idea to get your blood levels tested if you are in one of the higher-risk categories for heart disease. You may be called in by your doctor to have the tests.

These high-risk categories are:

• 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)
• A close family member has a cholesterol-related condition
• Being overweight or obese
• High blood pressure or diabetes
• Another medical condition such as a kidney condition, an underactive thyroid gland or an inflamed pancreas (pancreatitis), as these can all cause increased levels of cholesterol or triglycerides
• Diagnosed with coronary heart disease, stroke or peripheral arterial disease (PAD).