Thyroid testing

[seekingjenna71]

I have an appointment for testing in the afternoon. Do I need to be completely fasting or just not lake levo until after the test?

Thanks!

[Clutter]

Seekingjenna71,

It's advised to test early in the morning when TSH is highest and to fast (water only) as TSH drops after eating and drinking.

Your TSH will be lower because you are testing in the afternoon. I doubt it will make much difference if you don't fast. Certainly you should not take your Levothyroxine dose until after the blood test.

[seekingjenna71 in reply to Clutter]

Maybe I'll wait longer for a mirning appointment. Thankyou so much!

[SeasideSusie Remembering]

You really would be best cancelling your appointment and getting one at the very earliest appointment of the day. If you don't want your dose reduced, or are looking for an increase in dose, you want your TSH to be as high as possible in the range. TSH is higher early morning and lowers throughout the day.

Patient to patient tip always advised on here, which we don't discuss with doctors or phlebotomists.:

When booking thyroid tests, always book the very first appointment of the morning, fast overnight (water allowed) and leave off Levo for 24 hours. TSH is highest early morning and lowers throughout the day. It also lowers after eating.

[seekingjenna71 in reply to SeasideSusie]

Thankyou! My TSH was 0.11(0.2 - 4) in December she wants to reduce my dose and yet I feel I may need an increased dose. So I definately need to test in the morning!

[SeasideSusie Remembering in reply to seekingjenna71]

If she wants to reduce dose, make sure FT4 and FT3 are tested. Even if FT4 is high, as long as FT3 is in range you aren't overmedicated.

From thyroiduk.org/tuk/about_the... > Treatment Options:

Dr Toft states in Pulse Magazine, "The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.

In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.

But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.

This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."

You can obtain a copy of the article by emailing [e-mail] print it and highlight question 6 to show your doctor.

[mistydog in reply to SeasideSusie]

I've sometimes left it 48 hrs before a test, just to be sure

[SeasideSusie Remembering in reply to mistydog]

Leaving 48 hours won't affect the TSH, that's likely to give false low FT4 and FT3. For TSH it's the time of day and whether you have eaten that is important.

[seekingjenna71 in reply to SeasideSusie]

Fantastic 👍 Thank You so much

[DaveHunt13]

Hi..no... just go as normal... unless you get instructions from your Endo... you levels won't move enough in 1 day to matter and food intake doesn't really affect that test ( as far as I know)...I never fast for my thyroid tests...

[SeasideSusie Remembering in reply to DaveHunt13]

Eating lowers TSH. TSH is highest early hours of morning and lowers throughout the day. If TSH is an important factor in the results - say if you want an increase in dose or to avoid a reduction then TSH needs to be as high as possible - then an early morning fasting test will give a higher TSH than a test later in the day and after eating.

Daily Rhythms of Thyroid Hormones + TSH

healthunlocked.com/thyroidu...

There may be more but one member's endocrinologist has advised that Levo should not be taken in the 24 hours before testing.

[seekingjenna71 in reply to SeasideSusie]

I managed to get an early morning cancellation. Thankyou!

[DaveHunt13]

Ok good to know :). Thanks!