T3 and blood test: Hi I am having my bloods done... - Thyroid UK

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T3 and blood test

Lindsayf profile image
17 Replies

Hi

I am having my bloods done tomorrow and completely forgot this morning and took my normal dose of 100mcg T4 and 25mcg T3. I forgot to only take half of my T3 and then the other half 12 hours before my blood test.

Is it worth changing my appointment to Tuesday now?

Thanks

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Lindsayf profile image
Lindsayf
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17 Replies
Lindsayf profile image
Lindsayf

Thanks for that so annoyed at myself as I was so tired I completely forgot. I’ll do it for Tuesday and take half the 25mcg in the morning and the remaining in the evening on Monday. How many hours is the best result for T3 to show on bloods? 8-12 hours

SeasideSusie profile image
SeasideSusieRemembering in reply to Lindsayf

Lindsayf

I take half and half, some people split T3 into 3 doses.

8-12 hours is the time gap suggested here.

Lindsayf profile image
Lindsayf in reply to SeasideSusie

Thanks.... I’m dreading my results as I know exactly what the Endo will say! You TSH is suppressed and can’t be detected and they will want to start messing with my dosage.

SeasideSusie profile image
SeasideSusieRemembering in reply to Lindsayf

That's what my endo did back in 2002. He did manage to get my TSH to scrape back into range but didn't care how ill he made me as my FT3 had plummeted to 2.8 (2.8-7.1) although I was only taking Levo at the time. After 3 appointments I ditched him with the blessing of my GP but I still needed looking after for 2 years :(

Lindsayf profile image
Lindsayf in reply to SeasideSusie

Shocking... at what point can we say to an NHS Endo thanks for you advice but I am not prepared to change my dose. Can they over ride our decision and reduce the Levo as it’s on the NHS? Or do they have to get our permission to change it

SeasideSusie profile image
SeasideSusieRemembering in reply to Lindsayf

Lindsayf

I made a mistake, it wasn't TSH it was FT3 that plummeted to 2.8 (not had a coffee yet 🙄 although I have corrected it now).

After that appointment my then GP increased my Levo after making some derogatory remark about the endo.

I've never seen one since, I would refuse if offered, but still have a problem with suppressed TSH and the GPs at my surgery don't like it. I always point out that my FT4 and FT3 are well within range but they don't listen. They ignore me so I ignore them.

I went to the GP for something else very recently and it was blamed on me "taking too much thyroxine" despite the GP looking at an old test which had been sprung on me and I'd taken my thyroid meds that morning, so I had high FT4 as well as suppressed TSH. I was asked to reduce dose, I very politely refused asking that the GP look at my record and see I'd had the problem before and it was not linked to my thyroid. He just kept saying I must reduce my dose of Levo, I just kept politely telling him I wouldn't and would he consider and discuss the reason I had gone to see him not the thyroid. After the 5th time I politely said no I wouldn't reduce my dose he walked out of the room and left me there (how unprofessional!) but my prescription hasn't been altered. Can't wait for the next thrilling instalment of this game of ping-pong 🙄

Lindsayf profile image
Lindsayf in reply to SeasideSusie

I get told if your TSH is suppressed then you will get heart issues and osteoporosis. Do you want heart issues and thinning bones? It makes me so angry. I agree that my FT4 and FT3 need to be within range but I feel best when my TSH is suppressed.

I had a GP at my surgery try and tell me to reduce and I refuse to speak to them as my bloods were for ferritin and not thyroid yet they included them.

fuchsia-pink profile image
fuchsia-pink in reply to Lindsayf

It's a shame that the crucial but subtle distinction eludes so many doctors ... if you are NOT on thyroid meds and have very low TSH and way over-range free T3, yes that can be dangerous. If you are on thyroid meds and because of this your TSH is suppressed - well it's totally different!

But to keep the GP happy can you have a dexa bone scan so you can both see how healthy your bones are now, and as a useful benchmark for the future? x

Lindsayf profile image
Lindsayf in reply to fuchsia-pink

I would be happy to have one but they haven’t offered. I’ll ask for one if they say anything about thinning bones

SlowDragon profile image
SlowDragonAdministrator in reply to Lindsayf

I would split T3 dose into 3 day before test

12.5mcg waking. 6.25mcg 3pm and 6.25mcg 9pm (assuming test is 9am)

Also ......Hide your T3 and levothyroxine, so that you don’t take it when on auto pilot the morning before test

You might find splitting into 3 doses gives smoother results if take it this way every day

Lindsayf profile image
Lindsayf in reply to SlowDragon

Yes it was auto pilot this morning. I’m hoping to have my bloods done Tuesday between 8am and 9am. It’s sit and wait.

I have thought about splitting it into 3 but I’m always grazing and drinking juice throughout the day so having to think about having an empty stomach and taking T3 and then not drinking or eating for an hour after.

SlowDragon profile image
SlowDragonAdministrator in reply to Lindsayf

T3 isn’t as fussy as levothyroxine

I find taking at 3pm isn’t as issue (I move time back or forward a bit if necessary) to fit around afternoon tea

Lindsayf profile image
Lindsayf in reply to SlowDragon

How much time after eating and drinking do you wait to take dose 2 and 3? Also once you have taken them how long after do you leave food and drink? Thanks :) I hid my normal dose this morning so took my 100mcg and 12.5mcg. I’m hoping to have my bloods done tomorrow at 8.30am so will take my last dose of T3 at 8.30pm. No meds till after my bloods tomorrow :)

SlowDragon profile image
SlowDragonAdministrator in reply to Lindsayf

Typically

10mcg T3 waking around 6.30-7am

Cup of tea at 7.30-8am

lunch 12.30-1pm

5mcg T3 at 2.45ish

Cup of tea around 3.30pm

Evening meal 7ish

5mcg T3 11pm along with levothyroxine

jimh111 profile image
jimh111

That's fine, just take half your L-T3 tonight and your levels will be around mid-point by tomorrow morning.

Lindsayf profile image
Lindsayf in reply to jimh111

Would that still be the case if I took my full dose of T3 this morning?

jimh111 profile image
jimh111 in reply to Lindsayf

With a 24 hours half-life we store around two days worth of T3 in our blood (1 + 1/2 + 1/4 + 1/8 ...). So, just after taking a tablet you have 50 mcg T3 in your blood which falls to 25 mcg the next day just before that day's tablet. Average level is around 50+25/2 = 37 mcg.

Twelve hours after taking your L-T3 you will have about 70% left in your blood, i.e. around 35 mcg. If you then take 12.5 mcg it will go up to 47.5 mcg. Twelve hours later (the following morning of the blood test) you will have 70% or 37.5 which is around 33 mcg. So it is close to your average T3 level.

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