Apart from the fact that the test has to be at 9am, does one needs to consider coming off any supplements or medications?
And, with regards to an early morning test, would when someone actually wakes skew the results?
As always, thank you to all the knowledgeable people that have the care to share thier knowledge.
The saliva cortisol test has to be done 30 minutes after waking.
The blood cortisol test is 8.30 to 9.00 am. I assume that is because that is the average time when people's cortisol is highest. Someone with insomnia or a lark will not be average but at the bottom of the distribution, so yes, it will be distorted. The test will be after your cortisol peak and so distorted downwards.
If you are doing the test for a doctor - stay within the official time window.
If you are doing it for yourself, do it 30 mins after you wake.
That's my view anyway, interested to see what other people think.
Thank you so much.
I am not sure what is meant by bottom of the distribution? So, if I haven’t had a good night sleep the night before then the test result will falsely show low cortisol? Sorry. I’m clearly a bit confused by it.
Sorry. Cortisol levels are highest 30 minutes after waking. This is called the waking cortisol response (or something like that). After that it starts to go down.
If you are someone who because of insomnia or being an early riser wakes up much earlier than 8am then by the official testing time of 8.30 or 9am your cortisol will no longer be at its peak. So if you test at that time your cortisol will be lower than your actual waking cortisol Cortisol.
I believe that the standard waking cortisol test is timed at 8.30 to 9.00 because an average person wakes at 8.00 or 8.30 (this may not be true, but never mind).
An average person is in the middle of all the people who wake much earlier or much later. So if you are someone who wakes very early, the average time is not the right time to test your actual real life cortisol waking response. However, this is the medical standard. So if you are doing a test for a doctor, you should stick to the medical standard.
Thank you. That explains a lot.
One thing to remember for all early morning blood tests is to ensure sufficient hydration, we dehydrate overnight so if bloods at 9 I wake around 7 drink about 1/2 litre water so hydrated by 9. Similarly if dehydrated the day before it can skew results.
HRT will artificially raise cortisol levels as will the pill.
Thank you. That’s good to know.
Well, I had partial sleep night before, and can only hope there isn’t too much distortion. It’s all so difficult, so thank you to everyone for your help.
Cortisol test
Hashimoto's blood test and cortisol tests
Low Cortisol - Synacthen Blood Test
Nhs cortisol test
Saliva cortisol test 
