Health and Fitness Information Center

What you need to know about Cholesterol testing

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Analyses done in doctor's offices especially by someone not trained in laboratory techniques and on machines that are poorly standardized - may be particularly unreliable. And not all clinical lab methods for determining blood cholesterol levels end up with values that are comparable to those used by the Lipid Research Clinics.

Factors that affect your test:
Various factors unrelated to the lab can affect blood cholesterol levels. If it's winter, your reading will probably be higher. The cause of this seasonal shift is unknown, but it may be because people tend to eat fattier foods and to exercise less in winter. Even your body position at the time of blood withdrawal can influence the measurable concentration of blood lipids. When you are prone, your blood becomes diluted.

Still, there are measures you can take to ensure you are getting the best possible results from your cholesterol test:
1. Don't exercise before your test. Exercise can cause a temporary rise in cholesterol levels - as much as 10 to 15 percent - for up to an hour after you've stopped exercising.

2. Cholesterol levels can be affected by illness, some medications, pregnancy, and recent heart attack or surgery. If any of these conditions apply to you, discuss them with your doctor.

3. Sit down for at least five minutes before your blood is taken. Having blood taken while you standing or lying down can skew the results.

4. Don't eat anything for twelve hours prior to your blood test, if you are having your HDL/LDL levels measured.

5. Have at least two tests performed and schedule them a month or two apart. Since cholesterol levels fluctuate, the average of two tests will give a more accurate picture, provided both results are within thirty points of each other.

You're better off avoiding mass finger-stick cholesterol screening sites at the mall or other public places. Government surveys have shown that the personnel are often careless, poorly trained, and fail to follow standard safety and sanitary procedures. In addition, blood is often not drawn correctly - the finger is squeezed to extract blood rather than letting it flow freely - rendering the results worthless.