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Fasting vs non-fasting blood tests

Blood tests have traditionally been 'fasting' and 'non-fasting’. I was informed recently that the evidence suggests that the results are similar in both cases, e.g. cholesterol levels. Is that correct?

11 January 2019

Thank you for your question about the need of fasting when undergoing blood tests. A 2012 study showed that there was, indeed, minimal difference between a fasting and non-fasting cholesterol blood test. Whilst this stands true, it doesn’t apply to all the other tests that may require fasting.

A fasting blood test allows for your doctor to have a snapshot of your body without external interference from food, medication and other factors (you might be asked not to smoke or drink alcohol prior to some tests).

With a cholesterol blood test, levels of two types of cholesterol are measured: high-density lipoprotein (HDL) and low-density lipoprotein (LDL). These are both types of lipids. The study shows that there was no significant difference in the observed levels of HDL and LDL between fasting and non-fasting tests. The issue lies with the fact that the testing of cholesterol is often done in conjunction with tests for other lipids, namely triglycerides. These can be affected by food, to the extent that your doctor might feel the need to recommend dietary/lifestyle changes if levels are outside the healthy range.

If your main concern is the cholesterol you might be able to disregard the fasting factor.

However, other tests, such as blood-glucose, triglycerides will most certainly require a fasting period to portray an accurate snapshot of your body. As a rule of thumb our recommendation is for you to follow your GP recommendations.


2012 Article about Cholesterol testing Fasting vs Non Fasting

High Cholesterol - NHS factsheet

Answered by the Health at Hand team

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