Thyroid blood testing

My GP has asked for me to have a non-fasting blood test for TSH, is that normal? I thought we always needed to fast.

14 Replies

If you eat before the test your TSH will be lowered due to the action of the food and may not be given an increase in hormones:-

Thyroid-stimulating hormone is a marker of your metabolism, which refers to the rate at which you burn calories. A lower TSH indicates your metabolism is optimal, while a higher TSH represents a sluggish metabolism,

It is only recently we (thyroid) patients have been advised to fast before the blood test.

Thank you Shaws this is confirming what I thought. The endocrinologist has written to my GP asking for me to be given T3, the GP has refused to prescribe it once, and the endo has written again. I now have the blood test form from the GP. I think they are trying to argue that the endo is wrong in his request.

Thank you for your help. MariLiz

Your GP may be reluctant if he is aware of the cost of T3. Astronomical in the UK against the rest of Europe. There is only one licenced in the UK and the cost is astronomical compared to other countries.

Your GP can prescribe a cheaper T3 on a 'named patient basis' but that means he himself is responsible and most don't want that.

Remember leave at least 24 hours from your last dose and test.

I think that is the reason for the refusal initially. The endo had asked for 20mcg X 3 per day initially, but I funded my own at 20 mcg X 1 ( taken as two doses of 10) added to 50 mcg of Levo. This is what he has asked for now. Apparently the CCG in this area don't support it. If the GP refuses, I am planning on sourcing my own from abroad. Thank you again for your help. MariLiz

It may just be the bog standard form - my GPs forms always say non-fasting, but that's just because no one has up dated the computer, not because she's trying to slew the results.

Bet Shaws is right that the refusal is a money thing. There is constant pressure for more cash to be given to the NHS, but it's quite clear the stuff is thrown away. Their drug licensing programmes need a total overhaul - that's just a start.

Thank you for your reply. I think I will phone the surgery and ask ( innocently) if they have made a mistake on the form. See what the response is.

The surgery tell me you no longer need to fast for a thyroid blood test! So guess what, I will continue to do what I have always done!

Mariliz, there's never been a necessity to fast or have early testing for a thyroid test from a doctor's point of view. The advice to fast is patient-to-patient as research showed that TSH is higher early and fasting which can help borderline patients get a diagnosis, and patients with low TSH avoid a dose reduction.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

Thanks for that Clutter, the receptionist at the surgery tried to tell me it was a new ruling. However, when she went to check, they said I could do as I wished. I didn't want them to come back to me and say " Your TSH has fallen, therefore you don't need T3!" Me being suspicious I suppose. MariLiz

Try to have your blood drawn as early in the day as possible.

Will do! Thanks Muffy.

What would you consider to be early? Is 10.30am considered to be late? Could TSH levels differ to a noticeable extent if bloods are drawn 2 hours earlier?

The earliest appointment of the day, no later than 8.30 to 9am.

TSH is highest in the very early hours of the morning or around midnight to 4am and then starts to fall and is lowest in the afternoon.

See top chart in this thread

If you can make it, 8 - 9 am is the latest you should have blood drawn for a thyroid blood test.

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