Fasting or not for testing

[kushami36]

I’m getting thyroid blood tests tomorrow morning. Should I fast or not?

(I’m sorry, I’m unwell and cannot see which tests I’m having. Plus I’m in Australia and the abbreviations may be different.)

[jimh111]

There's no reliable evidence fasting makes any difference for thyroid tests. If you are having other blood tests you should check with the surgery.

[kushami36 in reply to jimh111]

Just had some extra ones added that do require fasting, so will get them all at once.

I wanted to check “with the experts” first

[greygoose]

If you're having thyroid tests then you're going to have TSH, I should imagine, and that's the same in most countries. And that's the one that fasting is likely to make a difference to. And there is some evidence that it does make a difference - especially coffee and tea. So, best to err on the side of caution and have breakfast after the test, just to be sure. What time is the blood draw?

[kushami36 in reply to greygoose]

In that case, I will fast just to be sure.

The test is at 9am. This is the only available time due to my being unwell and unable to travel to a collection point that opens earlier, unfortunately.

[kushami36 in reply to kushami36]

I have not been diagnosed with thyroid problems, just having it all checked due to comorbidities and some unusual muscle hypertrophy.

[greygoose in reply to kushami36]

9am is good. That's the best time to have a TSH test. And as that is really the only thyroid test doctors look at if needs to be at its highest to give a clear idea if there's a thyroid problem or not. After 9 am it drops sharply. So, if you're also fasting, you're doing everything right.