Cholesterol blood test: what it measures and what your result means

What is cholesterol?

Cholesterol is a fatty substance your body needs to build cells and make some hormones. Your liver makes most of it; the rest comes from food. It travels in the blood inside particles called lipoproteins.

The problem comes when too much builds up in artery walls. Over years this narrows the arteries and raises the risk of heart attack, stroke and circulation problems.

The parts of your result

• Total cholesterol: all the cholesterol in your blood added together.
• LDL cholesterol: the type that builds up in artery walls. Lower is generally better.
• HDL cholesterol: the type that carries cholesterol back to the liver to be cleared. Higher is generally better.
• Non-HDL cholesterol: total minus HDL. It counts all the harmful types together, and many doctors now use it in place of LDL.
• Triglycerides: a different blood fat, which rises with sugar, alcohol and excess calories.
• Cholesterol to HDL ratio: total cholesterol divided by HDL. A lower ratio is better.

Why is cholesterol tested?

• You are over 40, when the NHS starts routine heart checks
• A parent, brother or sister had heart disease or a stroke young, or has very high cholesterol
• You have high blood pressure, type 2 diabetes or kidney disease
• You smoke, are overweight, or want to see the effect of diet or exercise changes
• You take a statin or another cholesterol medicine and want to check it is working

What does a high result mean?

High LDL, non-HDL or total cholesterol means more cholesterol is available to build up in your arteries. Common reasons are:

• A diet high in saturated fat
• Not being active, or carrying extra weight
• Smoking
• An underactive thyroid, type 2 diabetes, or kidney or liver disease
• An inherited condition called familial hypercholesterolaemia, which runs in families and affects about 1 in 250 people

High triglycerides are often linked to alcohol, a diet high in sugar and refined carbohydrates, being overweight, or poorly controlled diabetes.

Low HDL is linked to inactivity, smoking and extra weight. Very low LDL is rarely a problem, and is often the aim of treatment.

What can affect your result?

• You don't usually need to fast for cholesterol. Triglycerides are higher after a meal, so if they come back high a doctor may repeat them after fasting.
• Some tests that include cholesterol ask you to fast. Follow the instructions for the test you book.
• A recent illness, surgery or pregnancy can change results for a few weeks
• Heavy drinking in the days before the test raises triglycerides

When to see a GP

Your results report shows the laboratory's range and flags results outside it. A doctor decides on treatment by looking at your overall risk of heart disease over the next 10 years, not cholesterol alone. Speak to your GP if:

• Any part of your result is flagged high, or HDL is flagged low
• You have a close family history of early heart disease or very high cholesterol
• You have diabetes, high blood pressure or kidney disease and haven't had your risk checked

Call 999 for chest pain, or for signs of a stroke: face drooping, arm weakness or slurred speech.