Summary

• Blood tests for cholesterol and other fats in your blood can help find out if you are at risk of developing atherosclerosis – a buildup of plaque in your arteries and blood vessels that can lead to heart disease and stroke. This is also known as cardiovascular disease or CVD.
• They are usually performed as part of a screening test called a Lipid Profile which measures different types of cholesterol together with another form of fat, called triglycerides.
• When assessing your CVD risk, your blood cholesterol levels will be considered along with other factors such as high blood pressure, obesity, diabetes and smoking.

What is cholesterol and why does it matter?

Cholesterol is a type of waxy fat that performs a range of important functions in the body. We cannot live without cholesterol. It’s found in every cell in our body and involved in a whole host of vital processes. All the cholesterol you need is made in your liver, and the rest comes from foods you eat.

Cholesterol cannot be dissolved in water and so it needs help to move through the blood, as blood is a liquid. It is processed in the liver where it is packaged up with proteins into lipoproteins. This enables it to move through blood rather than rising to the top, like oil on water. In this way, it travels to organs and tissues where and when it is needed.  

There are different types of lipoproteins depending on the amounts of fat and protein they contain. They are termed high-density lipoprotein (HDL) and low-density lipoprotein (LDL). There are also different subtypes of lipoproteins such as very low-density lipoprotein (VLDL) and intermediate density lipoprotein (IDL).

In general, lipoproteins with a higher fat content and lower protein content (e.g. lower density such as LDL and VLDL) are more likely to stick to artery walls and cause a buildup of plaques. Your body has systems in place for getting rid of excess lipids but sometimes these systems don’t work as they should, or they become overloaded.

What cholesterol levels are tested?

The lipid profile measures different types of lipoproteins in a blood sample and presents the information in different ways:

• Low-Density Lipoprotein (LDL) or ‘bad’ cholesterol is made mostly of cholesterol and less protein. This means they can deposit cholesterol into blood vessel walls causing plaques to form. By lowering LDL it’s possible to reduce the cholesterol inside plaques.
• High-Density Lipoprotein (HDL) sometimes called ‘good’ cholesterol is made up of more protein and less cholesterol. It helps remove cholesterol from artery walls. Having a normal HDL level is important.
• Total cholesterol is the measurement of all the cholesterol carried by lipoproteins in your blood sample.  
• Non-HDL cholesterol is a measurement of all the cholesterol other than HDL. It is your HDL or good cholesterol number subtracted from your total cholesterol number – a measure of all the bad types of cholesterol.
• Cholesterol/HDL ratio is reached by dividing your total cholesterol measurement by your HDL measurement. A higher ratio means you have a higher risk. It is thought to be a better predictor of heart disease and stroke risk.  
• Triglycerides is fat from the food we eat. High amounts of triglycerides in your blood can form plaques. They increase your risk of heart disease and stroke as well as your risk of pancreatitis.

Other, more specialised tests can be sometimes used including:

• Lipoprotein(a)
• Apolipoprotein- A-1
• Apolipoprotein- B-100
• Very low-density lipoprotein (VLDL) cholesterol

For more on cholesterol testing and what your results may mean see Lipid Profile.

Why get tested?

Your doctor may ask you to be tested if you:

• already have heart disease (angina, heart attack),
• have a family history of high cholesterol or of heart disease at an early age,
• are over 45 years,
• are less than 45 but have risk factors that put you at an increased chance of developing heart disease, such as diabetes, high blood pressure, chronic kidney failure or a kidney transplant, being of Aboriginal or Torres Strait Islander heritage, overweight or a smoker, or
• are taking drugs to lower your cholesterol level.

A higher-than-normal LDL-cholesterol level is one of the most important modifiable risk factors for diseases of the blood vessels and your risk of having a stroke or heart attack.

Having the test

Sample
Blood.

Any preparation?

In the past, you needed to fast before this test but now it is considered that fasting is not needed — in fact non-fasting is preferred by many laboratories. However, fasting for 8 – 12 hours may be required before a repeat test to confirm abnormal results. Only water is permitted. 

What can your results tell you?

Reading your test report

Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.

If your results are higher than they should be, a second blood sample should be taken on a separate occasion before a definitive diagnosis is made, as levels may vary between tests. Cholesterol levels fluctuate over time.

The measured cholesterol level may differ by as much as 10 per cent from one month to another. If you've been following a healthy diet and exercising but your cholesterol levels rise it may be due to these inherent fluctuations. Cholesterol levels measured over several months will give a good picture of the true state of your cholesterol.

Your medical team will make a judgement about whether LDL cholesterol lowering treatment should be started depending on your overall cardiovascular disease risk. This risk calculation includes other CVD risk factors such as high blood pressure, age, diabetes, and smoking. Your heart and stroke risk score can be calculated using the Australian CVD risk calculator. 

Your target cholesterol levels will depend on your personal situation and your assessed level of risk. Your doctor will specify whether or not you need to fast and this will be recorded in their notes to the laboratory. 

Traditionally, lipid tests were done on fasting samples. More recent guidelines suggest that non-fasting lipid tests are just as effective for most people. Non-fasting samples are more convenient and safer, especially for those with diabetes. However, fasting samples are still preferred in certain cases such as when a patient has high triglyceride levels or specific metabolic conditions.

Inherited high cholesterol levels - Familial Hypercholesterolaemia (FH)

About 1 in 250 people have a genetic change that increases their risk of having high LDL-cholesterol which puts them at a greater risk of heart disease earlier in life. This is called Familial Hypercholesterolaemia (FH). A genetic test for FH is available. For more information on this click here.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record.

You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.