At a Glance
Why Get Tested?
To determine your chances of developing cardiovascular disease
When to Get Tested?
Aged 40 as part of a routine cardiovascular health check, or if you are already thought to be at risk of cardiovascular disease for another reason, or to monitor your response to treatments which lower LDL-C.
A blood sample taken from a vein in the arm, or occasionally from a fingerprick
Test Preparation Needed?
Laboratory tests for LDL-C typically require a 12 hour fast; only water is permitted. Follow any instructions you are given.
The Test Sample
What is being tested?
Cholesterol is carried in the blood by proteins called “lipoproteins”. There are a number of different types of lipoproteins, which are named after how dense they are. LDL stands for ‘low-density lipoprotein’, and any cholesterol carried by LDL is known as LDL cholesterol, or LDL-C. LDL is considered to be undesirable because it deposits excess cholesterol in the walls of blood vessels and contributes to atherosclerosis, also known as 'hardening of the arteries' or ‘furring up of the arteries’, and ultimately cardiovascular disease, such as heart disease and strokes. Hence LDL-C is often termed 'bad' cholesterol.
LDL-C is usually tested as part of a lipid profile. This includes the total cholesterol as well as a “breakdown” of how much of that cholesterol is carried on LDL (ie LDL-C), and how much is carried on ‘high density lipoprotein’ (ie HDL cholesterol). Interestingly, HDL cholesterol seems to have a protective effect on the heart, and is therefore often termed ‘good’ cholesterol. Triglycerides are also measured as part of the lipid profile.
In fact, LDL-C is usually not measured directly, but calculated using an equation which uses the other components of the lipid profile. Occasionally LDL-C can be measured directly.
How is the sample collected for testing?
The test for LDL-C uses a blood sample. Most often, the blood sample is collected by venepuncture (using a needle to collect blood from a vein in the arm). Occasionally a fingerprick test can be used, although this is not commonly available in GP practices or hospitals in the UK.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
A test for LDL-C typically requires a 12-hour fast, with only water permitted during this time. Your doctor might recommend a slightly shorter or longer fast. Strictly speaking, if LDL-C is being measured directly, rather than calculated using an equation, fasting is not necessary – however, fasting will be required for other components of the lipid profile which are usually measured at the same time. Follow any instructions you are given.
Ask a Laboratory Scientist
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.