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Sunday 26th May 2019

Cholesterol test fast may not be needed

13th November 2012

Fasting before getting your cholesterol checked may not affect your blood test results, compared with not fasting, according to a recent Canadian study.


Fasting did not seem to change levels of triglycerides, HDL or LDL.

J Michael Gaziano, who wrote a commentary on the new study, said that the recommendation or requirement that people fast beforehand discouraged them from having cholesterol tests done.

He also said that the requirement produced an artificially heightened number of tests submitted in the mornings, leading to testing centers being  crammed with patients eager to end their fasts.

For the study, the researchers calculated average cholesterol levels for more than 200,000 people.

Such measurements are used by doctors, who may or may not prescribe statins.

The people studied had either eaten just minutes before, or not for 16 hours.

While a minority of people who had cholesterol tests done did indeed show a difference in HDL and LDL, most people's non-fasting serum levels did not differ from their serum levels while fasting.

The researchers found that there was a 2% variance in people's HDL and LDL over that time span.

LDL, commonly thought of as the 'bad' type of cholesterol, did vary by up to 10%, while triglyceride levels tended to vary by up to 20%.

But since people's total cholesterol levels are typically composed of mostly HDL, the LDL variation did not really affect people's serum cholesterol levels.

These numbers are typically used by doctors to calculate the heart health of a patient.

The average age of the study participants was 53.

The average total cholesterol was 183 mg/dl, putting them all in a relatively low risk group.

The American Heart Association recommends that people have no more than 200 mg/dl of LDL in their blood serum.

Now, it seems that patients who already have high triglyceride levels or diabetes should continue to fast before their tests, while people who do not currently suffer from such problems do not need to do so.

The majority of patients, whose cholesterol is composed mainly of HDL, do not need to fast, as it should not affect the outcome of their tests.

Gaziano said that the recommendation also caused logistic challenges, leading not only to long lines in the mornings but to long waiting times, as well as the prospect that patients would not show up for further tests.

He said that patients could discuss the prospect of fasting or not fasting with their doctors, though the practice of fasting before a cholesterol test would probably continue to be seen as normal.

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