Why are blood cholesterol levels measured?

A cholesterol blood test tells us important information about the amount and types of different fats in the bloodstream. These fats found in the bloodstream include cholesterol and triglycerides. Triglycerides are the most common form of fat in your body. If the levels of triglycerides in your blood are too high, they can affect your blood cholesterol levels.

Why do blood cholesterol and triglyceride levels go up?

Your liver produces about 80% of the cholesterol in your body. The rest of the cholesterol comes from the food you eat, and is called dietary cholesterol. There are two kinds of cholesterol: “bad” cholesterol or LDL (low-density lipoprotein) and “good” cholesterol or HDL (high-density lipoprotein). The type and amount of fats you eat can affect your levels of either “good” HDL or “bad” LDL.

High triglyceride levels are often associated with drinking too much alcohol, being overweight, or having poorly controlled diabetes.

If I have too much cholesterol and triglycerides in my blood, what happens?

Some people have too much cholesterol in their blood. This condition is called hypercholesterolemia or dyslipidemia. It is a major risk factor for coronary artery disease, which is a condition that can lead to heart attacks and stroke.

When there is too much cholesterol in the blood, the excess can settle on the inside of the blood vessels. Over time, fatty deposits called “plaque” build up in the blood vessels. Plaque clogs the blood vessels so that blood can't flow properly. When blood flow is obstructed, the chance of a heart attack or stroke increases. High triglyceride levels increase the tendency for the blood to clot. Blood clots can also obstruct blood flow and the risk of a heart attack or stroke goes up.

Who should be screened for high cholesterol levels?

The 2003 Recommendations for Dyslipidemia Management in Canada says that, although any person can be screened for high cholesterol levels, screening for high cholesterol is specifically recommended for:

  • men over 40 years of age
  • women who are postmenopausal or over 50 years of age
  • people who have diabetes
  • people who have risk factors such as hypertension, smoking or abdominal obesity
  • people who have a strong family history of premature heart disease or stroke
  • people who have physical signs of high cholesterol (for example, fatty deposits under the skin,called xanthoma or xanthelasma)
  • people who have evidence of vascular or coronary artery disease (either with or without symptoms).

How are blood cholesterol test results interpreted?

Doctors interpret blood cholesterol test results by examining each person's risk factors. The doctor looks at the presence or absence of risk factors such as existing heart disease, diabetes and other medical and lifestyle conditions to determine the person's chance of dying from heart disease or having a non-fatal heart attack within 10 years. The doctor will place the patient in either a high, intermediate or low risk category, and can then create an effective treatment plan for that person, either with lifestyle changes, medication or both.

Additional resources

Prepared by Alberta Health Services. This FAQ appeared originally on the Canadian Health Network Web site.

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