Type 2 2 how long to fast before blood tests

I've always fasted for at least 12 hours before all my tests as that's the requirement for lipids. Recently I heard that fasting blood sugars should be tested only at maximum 10 hours and a longer fast would give false readings. Can anyone explain this? Should I ask the lab to do two separate draws two hours apart.

xfieldok said:

Where did you hear this?

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I can not find a written statement about the blood sugar maximum fasting time, just a remark from a GP in a hurry that it should not be more than 10 hours.
But I did find this one, about lipids, just as puzzling . Capital Pathology
http://www.capitalpath.com.au/patients/faq.aspx
"DO I NEED TO FAST?
Not all tests require fasting beforehand. However, there are some tests which will require you to fast for 8 - 12 hours, for example cholesterol, lipids, fasting glucose. Fasting should not exceed 12 hours. "
and this :
http://www.capitalpath.com.au/media/52449/fasting.pdf
2. Do not fast for any longer than 12 hours, as this may affect your test.

I wonder why ?

britishpub said:

Unlikely.

It sounds like made up nonsense.

8 hours, 10 hours, 12 hours it will be all be guesswork with little or no evidence to back it up.

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capitalpath.com.au say this:

No appointment is necessary for this test Your Doctor has referred you to have a ‘fasting’ blood test. To ensure reliable and accurate test results, it is important that you follow these instructions carefully.  Please ensure that you have nothing to eat or drink (you may drink water) for 8-12 hours prior to presenting for the test. It is recommended that you fast for 8 hours for a ‘Fasting glucose’ and 10-12 hours for ‘cholesterol/lipid’ testing. 

Do not fast for any longer than 12 hours, as this may affect your test.

 Ensure that you drink plenty of water to stay well hydrated.  Smoking should be avoided.  Continue to take any prescribed medications, unless advised otherwise by your doctor. Early morning appointments are available at most of our Collection Centres. Please phone your most convenient Collection Centre to make an appointment. For further information on the blood test procedure please see the Patient Information Sheet titled “What To Expect From My Blood Test”.