T3 dosing - blood test tomorrow morning - quick... - Thyroid UK

Thyroid UK

120,343 members140,089 posts

T3 dosing - blood test tomorrow morning - quick advice please

Josephineinamachine profile image

Hi sorry - just want to be absolutely sure I have this right. I take my Levo and Lio at 4am every morning. I don’t split my dose. Am I correct in that I just leave my dose tomorrow morning before the blood test and then take it after? I don’t have to split the Lio and take some tonight do I? Because that wouldn’t feel good… 😳

Thank you!


20 Replies
SeasideSusie profile image

It would have been better to split today's dose of T3 into 2 or 3 portions and take the last portion tonight, 8-12 hours before the blood draw. This gives the best measure of normal circulating hormone.

Last dose of Levo should be 24 hours before the blood draw.

It's better to follow these timings just for the one day.

If I understand correctly, you have taken them both at 4am today? Then you will have false low FT4 and FT3 results. If you take anything in the morning before the test you will have false high results.

Oh I thought I read somewhere that it would be okay to treat the Lio the same as Levo when taking the test. Would it be better then to rearrange the blood test for next week do you think SeasideSusie ?

And thank you for the quick response SeasideSusie !

SeasideSusie profile image
SeasideSusieAdministrator in reply to Josephineinamachine

If you want accurate results then it's 24 hour gap from Levo to blood draw and 8-12 hour gap from last portion of T3 dose. To blood draw, adjusting times day before if necessary, and splitting dose of T3.

Because I am on t3 liothyronine my TSH is suppressed and neither GP or I bother about that. I therefore have my blood tests at the time that fits in with my lio dose. So I always arrange my blood test for 8 hours after lio. I adjust my levo dose to be 24 hours before.

Hi Lalatoot so that would mean I have my blood test in the afternoon at about 12noon if I don’t take the Levo that morning?

Yes. That is the way I do it for simplicity. As long as you are consistent so each blood test is done the same way then you can follow like for like,

Right, thank you! That makes sense. I don’t want to mess with the timings of my T3 if at all possible. I’ll ring tomorrow morning to see if I can get an appointment early afternoon. If not I’ll try again for the next day… thank you!! 😊

SlowDragon profile image

What vitamin supplements are you currently taking

If taking any supplements that contain biotin important to stop a week before test

Same with iron supplements if testing ferritin levels

If you leave more than 24 hours between last dose levothyroxine and especially for T3 test, you will have false low Ft4 and falsely low Ft3

We always recommend splitting T3 into 3 smaller doses day before test, with last 1/3rd of daily dose 8-12 hours before test

Hi SlowDragon thank you for responding so late. I’ve clearly banjaxed the whole thing so I’ve just cancelled the blood draw for tomorrow 🙄 and will rearrange for next week. I’m worried splitting the dose is going to make me feel awful! I like Lalatoot’s suggestion because then I’m not messing it around too much. Do you know why it’s best to do Medichecks at the beginning of the week rather than later? I’m not on anything with biotin or taking iron so that’s okay 😊 thank you

SlowDragon profile image
SlowDragonAdministrator in reply to Josephineinamachine

You don’t want to post bloods back to arrive at weekends

Post service can take 2 days to arrive

It shouldn’t make any difference splitting dose for one day

How much T3 are you currently taking

SlowDragon profile image

If you normally take levothyroxine at bedtime/in night ...adjust timings as follows prior to blood test

If testing 9am Monday morning, delay Saturday evening dose levothyroxine until 9am Sunday morning. Delay Sunday evening dose levothyroxine until after blood test on Monday morning. Take Monday evening dose levothyroxine as per normal

Thank you. I’m on 10 mcg Lio. I take Levo and Lio at 4am. So if I get a 9am appt for next Monday I take Levo 9am Sunday morning. Then take 5mcg Lio same time and 5 mcg around 9pm Sunday night? I was going to report I felt less brain fog lately, but now I’m not so sure!!

Do you feel better taking the single dose? Just wondering 😊

Hi yes I do thank you! 😊I had a day last week on Monday when I had to teach all day face to face. I was really anxious about it - my memory and that awful fatigue. In fact only got 3 hours sleep the night before. Anyway, I did /and it was fine. I felt a bit desperate but I don’t think it showed. I was fast asleep by 8.30 that evening and slept like a log. I woke the next morning and it was if a light had come on. Fatigue gone, brain fog gone (more or less). Since then I’ve had consistently good days (yesterday a bit tired but not too bad). I’ve achieved a lot of housework (which sounds sad but oh the joy of being able to motivate and keep going!) and a lot of work and had some positive family time. I’m very hesitant to post this though as it seems every time I post ‘I’m okay!’ I go downhill fast!

How are you doing? Are you still doing well? 😊

Im going to risk being positive…and here goes…!

Oh, I’m SO pleased to hear all this 😊 I know exactly what you mean about the improved mental acuity - it’s been like going from night to day for me, and a couple of peoplehave commented .

And I also understand about having the energy to do housework! I have experienced the same feeling. I do still get tired but more ‘normal’ tired I would say . I still think it’s a miracle if I manage to stay awake for an evening .

I’ve continued with morning and afternoon dosing but have been thinking about trying a single dose - I’m planning to do a blood test soon so think I’ll try the change after that .

I’m also eating so much better and enjoying food more than I have for ages - I have a proper appetite again .

I’m SO delighted to hear how you’re doing ! 😊

Aww THANK you!! You too! Oh good luck if you’re going to change the dose regime. It honestly took about 6 weeks for the light to start coming on - maybe 7? 🤔 So you may need to give your body that time to adjust I guess. Please let me know how you get on? Good luck with your test! X

This is my 7th week so I plan to test on Monday - and will try it after that 😊What a pair of super women we will be !!

Absolutely! Lol. My test is Monday too now after messing up today 🙄 we shall be catching up next week I think! 😊

Oddly enough - I tried to do a test yesterday and dropped it and ruined it ! So next Monday it is 😂

You may also like...