Summary

• Blood tests for cholesterol and other fats in your blood can help find out if you are at risk of developing heart disease or stroke.
• They measure the different types of cholesterol in your blood and are usually performed as part of a screening test called a Lipid Panel.
• This includes cholesterol, LDL or low-density lipoprotein cholesterol and HDL or high-density lipoprotein cholesterol, non-HDL-cholesterol as well as triglycerides, another form of fat.
• Your blood cholesterol levels will be considered along with other risk factors such as high blood pressure, obesity 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, like meat and dairy. High amounts of cholesterol in your blood can lead to health problems.

Cholesterol is carried around the bloodstream in lipoproteins.  All cholesterol is the same – it’s the lipoproteins that carry it that are different, and this is what matters.

Lipoproteins are round particles of fat and proteins that travel in your bloodstream to cells throughout your body. Cholesterol and triglycerides are two types of lipids found in lipoproteins. 

Different types of cholesterol

There are several types of lipoproteins, and the main ones are High-Density Lipoprotein (HDL) sometimes called ‘good’ cholesterol and Low-Density Lipoprotein (LDL) or ‘bad’ cholesterol. When cholesterol is carried by HDL it is called HDL–cholesterol and when it is carried by LDL it is called LDL–cholesterol.

• LDL (low-density lipoprotein) deposits cholesterol into blood vessel walls causing plaques to form. By lowering LDL it’s possible to reduce the cholesterol inside plaques.
• HDL (high-density lipoprotein) helps remove cholesterol from artery walls. Having a normal HDL level is important.

How plaques form

LDL– cholesterol sticks together with other fats, cells, calcium and debris floating around in the bloodstream and forms plaques in the walls of arteries. The build-up of plaque narrows the space within the artery.  

Over time, a tough, fibrous cap or scar forms over the soft sticky plaque and if this breaks open – say, if your blood pressure spikes – a blood clot forms over the rupture. This blocks the blood flow which can lead to a heart attack or stroke. There are different types of plaques. Some grow slowly and may never cause problems, even when the plaque is large enough to restrict blood flow through the artery.

The most dangerous type of plaque is an unstable plaque. In these plaques, the cap on top of becomes thin and weak, which makes it more likely to burst. Most heart attacks occur when small plaques break open.

By reducing cholesterol from the plaques, you can reduce your risk of heart attack or stroke. It’s possible to do this by lowering the amount of LDL travelling around in your blood.

Lipoprotein(a)

Lipoprotein(a) or Lp(a) is another a type of bad lipoprotein. In Lp(a), the LDL particles are stickier. Lp(a) is a type of LDL that contains a protein called apolipoprotein(a). High Lp(a) levels have been linked to a higher risk for heart disease, heart attack and stroke. A tendency to having high Lp(a) levels runs in families – a person’s Lp(a) level is due more to their genes than to factors like diet. People with severe kidney failure may also have high levels of Lp(a).

Lp(a) is not included in the routine lipid profile. However, your medical team may request it to decide on your risk of heart attack if you have a strong family history of heart attack at a relatively young age.

It can sometimes be ordered if you already have had a heart attack, have heart disease or another vascular disease but the results of your lipid tests are normal.  This is because many people who have heart attacks have normal cholesterol levels, and their doctors are looking at other factors that may have an influence on heart disease, such as high Lp(a) levels.

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.