Cholesterol Blood Test

Cholesterol is an essential fat (lipid) in the body. Although it has a bad reputation it has some important functions, including building cell membranes and producing a number of essential hormones including testosterone and oestradiol. Cholesterol is manufactured in the liver and also comes from the food we eat. Although there are a number of different types of cholesterol, the two main components of total cholesterol are HDL (high density lipoprotein) which is protective against heart disease and LDL (low density lipoprotein) which, in high levels, can contribute to cardiovascular disease. Your total cholesterol result on its own is of limited value in understanding your risk of heart disease; high levels of HDL cholesterol can cause a raised total cholesterol result but may actually be protective against heart disease. Equally, you can have a normal total cholesterol level but have low levels of protective HDL cholesterol. The most important factors are how much HDL and LDL cholesterol you have, and what proportion of your total cholesterol is made up of protective HDL cholesterol. We give a detailed breakdown of the components of your total cholesterol in the rest of this cholesterol profile.

LDL cholesterol (low-density lipoprotein) is a molecule made of lipids and proteins which transports cholesterol, triglycerides and other fats to various tissues throughout the body. Too much LDL cholesterol, commonly called ‘bad cholesterol’, can cause fatty deposits to accumulate inside artery walls, potentially leading to atherosclerosis and heart disease.

Your total cholesterol is broken down into 2 main components; HDL (good) cholesterol and LDL (bad). There are more types of harmful cholesterol in your blood than just LDL – these include VLDL (very low-density lipoproteins) and other lipoproteins which are thought to be even more harmful than LDL cholesterol. Non-HDL cholesterol is calculated by subtracting your HDL cholesterol value from your total cholesterol. It therefore includes all the non-protective and potentially harmful cholesterol in your blood, not just LDL. As such, it is considered to be a better marker for cardiovascular risk than total cholesterol and LDL cholesterol. The recommended level of non-HDL cholesterol is below 4 mmol/L.

HDL cholesterol (high-density lipoprotein) is a molecule in the body which removes cholesterol from the bloodstream and transports it to the liver where it is broken down and removed from the body in bile. HDL cholesterol is commonly known as ‘good cholesterol’.

The cholesterol/HDL ratio is calculated by dividing your total cholesterol value by your HDL cholesterol level. It is used as a measure of cardiovascular risk because it gives a good insight into the proportion of your total cholesterol which is good (i.e. high-density lipoprotein HDL). Heart disease risk tools (such as QRisk) use the cholesterol/HDL ratio to calculate your risk of having a heart attack.

Triglycerides are a type of fat (lipid) that circulate in the blood. After you eat, your body converts excess calories (whether from fat or carbohydrates) into triglycerides which are then transported to cells to be stored as fat. Your body then releases triglycerides when required for energy.