Thyroid UK
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Fasting cortisol test

Hi, I'm looking for some advice. My rheumatologist has requested that my GP carry out a Fasting cortisol test, anyone know what's involved and how to get the best results.

They have also suggested again that I have Chronic Fatigue and should be referred to a self-management program and a screen of sleep apnoea.

I am currently taking T3 and T4 medication.

Any advice about the cortisol tests would be very gratefully received.


4 Replies


I'm sorry you've had no replies about the cortisol fasting test. Feel free to repost your question.

Before accepting a diagnosis of CFS I would increase your T3 dose until FT3 is in the top third of range ie 5.5 - 6.8.


Thanks Clutter


This document is very helpful :

There is no need to read it all! Do a page search for the word cortisol and find the tests that may be relevant to you. It will tell you all you need to know about timing of test, fasting, what to expect, and what the results might mean.

The document is for doctors, but I've found it useful as a reference for patients even though I don't expect to understand much of it.

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Thanks for the link, I won't be able to read it on my phone but will download it onto a PC later

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