Thyroid UK

What supplements should I cease before test?

I've finally achieved an appt with my chosen endocrinologist after they tried to fob me off with an endocrinologist that has been said to be very unknowledgable and unhelpful.

I will need to take test for the following before the appt:


Thyroid antibodies


Liver Function Test


Blood sugar test



Should I stop NDT before test and if so how long before?

Should I stop taking Seriphos before test and how long before?

Anything else I should do to prepare?

14 Replies

CC, don't take your NDT the morning of your thyroid blood tests. Take it after. Blood sugar should be a fasting test ie nothing after 9pm the night before other than a few sips of water.

I don't know whether you need to stop Seriphos for the cortisol test.


Hi Clutter, thank you. It's odd that with the test there is a letter stating no need to fast, perhaps a mistake. I will try to call endocrinlogist secretary to check. Would make more sense to fast, but if they insist I don't need to, less trouble for me.


CC, if the letter says no need to fast, it should be fine. I may be confusing it with something else.


I doubt it, their pretty incompetent.


CC, there are two types of blood sugar test, fasting and random. Random doesn't require fasting.


Thank you Clutter, I will check with them.


In your shoes I would fast for 12 hours other than drinking water. I always do this unless there is a very good reason why I shouldn't. I think it maximises the comparability between tests if I keep the timing and the conditions the same as far as possible.

Also I thought blood sugar testing was always done fasting. If it isn't done this way the results would depend on what you had for breakfast. Imagine the difference there would be in your blood sugar if you had Frosties for breakfast, compared to a fry up, compared to a boiled egg, compared to just a mug of coffee. I'm sure they would all affect your blood sugar in different ways. So fasting is the only thing that makes sense. Make sure the person doing the test knows you've fasted and for how long.

As regards the cortisol, these are lists of things which can affect saliva test cortisol levels and I'm guessing the same list would apply to blood tests. Which ones you give up is up to you of course - I've had saliva testing done but I couldn't give up everything it suggested - it just wasn't practical.

There is a limit to how far I will go to get accurate results!

1 like

Thank you very much humanbean. I doubt that the cortisol will be tested via saliva testing.


I'm sure it won't be. But it seems reasonable to assume that some supplements and medications will affect the cortisol result however it is tested. :)

1 like

Thank you humanbean, Yes, I will be giving in a list of my meds at appt.


When I first met my new Endo I didn't take my thyroid meds expecting that he would do Thyriod meds. Yes he did but also did many others! I got a letter saying my random glucose was nearing diabetic levels and could I get the surgery to repeat a fasting one and then s glucose tolerance test if still giving high readings. So I had to repeat a fasting on and it was fine. I only managed to make my Endo appointment by swigging cough mixture by the bucket load so I has a reason for it to be high!

When I've had thyroid bloods at the surgery I always fast but the nurse said in that case to tell her so she can tick the box on the form and it cuts out the time wasted if labs then ask for a fasting and have destroyed your original bloods. She and I agreeded a fasting gives a more accurate baseline so easier for comparisons.


Thank you silverfox. So the first test was random glucose so no fasting. But when the reading was high, so a fasting test was done to establish? But first one was high due to cough mixture. I think I might fast in that case for both glucose and thyroid and remember to tell nurse that I have done so.


Hi Any thyroid meds that morning and Beta Blockers, rest OK.



Thank you Jackie.


You may also like...