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cholesterol test

Alternative Names
total cholesterol

This test measures the total amount of cholesterol in the blood. It is generally done together with blood tests that measure a person's HDL cholesterol and LDL, or "bad cholesterol".

Since high levels of cholesterol are often associated with cardiovascular disease, the test is done to evaluate a person's heart disease risk. It may also be ordered to detect disorders of the thyroid gland, kidney or other body organs.

Cholesterol is attached to fatty molecules called lipoproteins, which are carried in the bloodstream. The two major lipoproteins are low-density lipoproteins (LDL) and high-density lipoproteins (HDL). HDL transports excess cholesterol to the liver for excretion in the bile, a liver product that helps with fat absorption and that excretes waste products. It is known as the "good" cholesterol. LDL leaves fatty deposits on the wall of the arteries, a condition called arteriosclerosis, and is known as the "bad" cholesterol. Therefore, the ratio of LDL to HDL is a measure used to evaluate risk for heart disease. A low LDL:HDL ratio means lower risk, and vice-versa.

How is the test performed?
A blood sample needs to be taken in order to measure the level of blood cholesterol. The blood is usually drawn from a vein in the forearm or the hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube called a tourniquet is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial. The sample is sent to the laboratory to be analysed. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

What is involved in preparation for the test?
Individuals should request specific instructions from their doctors about how to prepare for this test.

What do the test results mean?
Normal values for total blood cholesterol range from 3.6 to 7.7 mmols/L (millimoles per litre). The best range is from 3.6 to 5.7 mmols/L.

Abnormally high levels of blood cholesterol may indicate:
  • arteriosclerosis
  • biliary cirrhosis, which is scarring and blockage of the bile ducts
  • familial hyperlipidaemia, a condition in which high blood lipids run in a family
  • high-cholesterol diet
  • high stress
  • low thyroid activity, called hypothyroidism
  • heart attack, known as myocardial infarction
  • nephrotic syndrome, which is a kidney disease resulting in loss of protein in the urine
  • uncontrolled diabetes
Abnormally low levels of cholesterol may indicate:
  • an overactive thyroid, called hyperthyroidism
  • liver disease
  • inadequate absorption of nutrients from the intestines, or malabsorption
  • malnutrition
  • pernicious anaemia, which is low red blood cell count from vitamin B12 deficiency
  • infection
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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