Summary

• LDL-cholesterol is often termed ‘bad’ cholesterol because it increases the risk of atherosclerosis – a buildup of plaque in your arteries and blood vessels that can lead to heart disease and stroke (known as cardiovascular disease or CVD).
• It is part of the Lipid Profile group of tests which measures different types of cholesterol and another form of fat, called triglycerides.
• When assessing your CVD risk, your results will be considered along with other factors such as high blood pressure, obesity, diabetes and smoking.

What is LDL-cholesterol?

Low-density lipoprotein (LDL) cholesterol is often termed bad cholesterol because it deposits excess cholesterol in artery walls creating a narrowing of the arteries.

LDL-cholesterol is included in the Lipid Profile group of tests which measures different types of cholesterol and another form of fat, called triglycerides.

The lipid profile test is used to predict your risk of developing CVD in the next 5 or 10 years. Your results are considered along with other risk factors such as high blood pressure, obesity, diabetes and smoking.

Although lipids are essential for many of your body’s functions, having too much of low-density types of lipoproteins in your blood is harmful. 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. Some people inherit genetic conditions that cause them to have too much low-density lipoproteins at a young age and they are at a high risk of a heart attack or stroke.

How too much LDL-cholesterol can be harmful

Cholesterol cannot be dissolved in water and so it needs help to move it through the blood as blood is a liquid. Cholesterol is made 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 sub-types of lipoproteins.

In general, lipoproteins with a higher fat content and lower protein content are more likely to stick to artery walls and cause a buildup of plaques. For more on lipoproteins see Lipid Profile.

There are also sub-types of LDL-cholesterol including Very Low-Density Lipoproteins (VLDL), lipoprotein (a) (Lp(a)), and apolipoproteins A-1 and B-100 (apoA1 and apoB) among others.  In certain circumstances, these may be measured separately.

Cholesterol contained within LDL makes up about 80 per cent of total cholesterol in a healthy person. The two main drivers of LDL levels are:

• Genetic inheritance – this is responsible for more than half of the number of cases of high LDL levels and is not modifiable, except by medication.
• Diet – this is of variable effect from person to person. Most of the effect of diet to lower LDL-cholesterol levels is achieved within the first two weeks.

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 see Familial Hypercholesterolaemia.

Children who have a family history of very high LDL cholesterol or premature cardiovascular disease (generally considered to be a first-degree relative with heart attack or stroke before age 55 if male, or 60 if female) should have a lipid profile once they reach five. This is because they may have an inherited condition and will benefit from early treatment.

Why get tested?

LDL-cholesterol is most often requested with tests for other forms of cholesterol as part of the lipid profile, which is recommended as routine tests to assess your CVD risk. For more on this see Lipid Profile.

Having the test

Sample

Blood.

Any preparation?

Fasting lipid testing and random lipid testing are two approaches to measuring lipid levels in your blood:

• Fasting Lipid Testing: You need to fast for 8-12 hours before the test, meaning you should not eat or drink anything except water before you blood sample is collected. Fasting means that recent food intake will not affect your test results, providing a more accurate measurement of your lipid levels.
• Random Lipid Testing: This test does not require fasting, so you can eat and drink normally before the test. More recent studies show that random (non-fasting) lipid testing can provide accurate results, and it is more convenient and safer for people with diabetes as they do not have to fast.

Your results

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.  

For a table of the results of cholesterol and triglycerides tests see Lipid Profile.

There is no normal or ideal LDL-cholesterol level. Instead, guidelines recommend that an individual approach should be taken in assessing your risk which is based on your personal test results and health history.

The laboratory performing your tests will flag your results for further scrutiny if your LDL-cholesterol level is 3 mmol/L or higher. If you are started on treatment, the target level for LDL-cholesterol is usually less than 2.0 mmol/L although your medical team may decide that a different target is more appropriate for you. It is important to remember that any reduction in LDL cholesterol reduces the risk of heart disease and stroke, even if you do not meet your treatment target.

How your LDL-cholesterol is measured

Low-density lipoprotein (LDL) cholesterol is commonly measured using two different methods:

• Direct Measurement: The LDL cholesterol is directly measured in your blood. It's the most accurate method. It is especially useful when triglyceride levels are high, which can affect calculated methods.
• Friedewald Formula: This method is used to estimate LDL-cholesterol levels. The formula is LDL cholesterol = Total cholesterol - HDL cholesterol – Triglycerides/2.2. It is often used in routine lipid profiles when triglyceride levels are below 4.5 mmol/L.

Conditions that can affect your LDL-cholesterol levels

LDL cholesterol may be falsely low if you are acutely unwell at the time of measurement (for example, if you have an infectious disease, if you are recovering from a heart attack or have recently had surgery). You should wait at least six weeks after any illness to have LDL-cholesterol measured.

Cholesterol is high during pregnancy. Pregnant women should wait until at least six weeks after the baby is born before having LDL-cholesterol measured.

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, medications 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.