I Realized I don't understand something - T3 be... - Thyroid UK

Thyroid UK

141,235 members166,485 posts

I Realized I don't understand something - T3 before blood tests

Recon profile image
11 Replies

Hi All,

I may be dense, and I have read that splitting your T3 into smaller sections the day before a blood test is important. I didn't think this applied to me, as I take my little bit of T3 in the morning with my levo, and so I ended up going for over 24 hours without the T3 (I didn't take either T3 or T4 that morning). Can someone explain to me what, exactly is the benefit of splitting the dose, and having it be approximately 8-12 hours prior to testing? I realized I don't understand the reasoning/biology/bio-chemistry behind this, and would like to make some sense out of it (if my dense-ness can lift!)

Thanks!

Written by
Recon profile image
Recon
To view profiles and participate in discussions please or .
Read more about...
11 Replies
Lalatoot profile image
Lalatoot

Recon - T3 rises to its peak in your blood 2 to 4 hours after you take your dose. You can test your levels 2 to 4 hours after your dose - this will give you ft3 at its highest. Many of us don't want to know the peak result, we want to know the level when its lower both for keeping ourselves adequately medicated and for the reason that for most of the day our ft3 is not at peak level. We like to test 8 to 12 hours after a dose.

Whatever you do it is important to do the same for each blood test so you are comparing like for like.

I take my levo and lio in 2 daily doses, morning and bedtime. My testing protocol is that I test at 2pm (I am not worried about TSH being lower at this time of day) I take my usual dose of levo and lio at 10pm ish the night before. The morning of my test I take my lio only at 6am ish. This gives me 8 hours between my lio dose and test and 16 hours between levo and test.

That way I feel I am measuring the lower levels of ft4 and ft3.

There is some debate on here as to how significant a difference taking your levo before a blood test makes. The important thing is consistency so you can compare like for like over time.

Recon profile image
Recon in reply toLalatoot

ok, so if I only take the t3 in the morning, on the day that I test, I will refrain from taking it until after the blood draw. Am I correct? (again, dense-disclaimer!)

tattybogle profile image
tattybogle in reply toRecon

These graphs show what happens to blood levels of fT3 , fT4 and TSH in the 24 hours following the last dose. The top graph is fT3 levels.. and the top line in that graph (the one with the big lump at the start) is what happens to fT3 levels after taking T3 tablet ( the lower line is what happens to fT3 levels after taking a levo tablet)

If you test 24 hrs after taking the last T3 tablet .. then the result you get will be the very lowest amount of fT3 you normally have every day .

If you test more than 24hrs after last dose the result will be lower than anything you normally have.

To get the average level you would test about 8-12 hours after last dose .

To see the very highest level you normally have , you would test after about 2-5 hours.

There will of course be slight individual differences in how fast the dose is absorbed from the gut, but these timings are the best guess we have based on what we know from research.

.
Recon profile image
Recon in reply totattybogle

Thank you!! As a visual learner - the graphs are great.

Venicefan profile image
Venicefan in reply totattybogle

Hi tattybogleHave you got a link for the research article that you got the graphs from? I’d really like to read it. 🤗

tattybogle profile image
tattybogle in reply toVenicefan

The summary and images are here, but the full thing is behind a paywall semanticscholar.org/paper/T...

i pinched the image from Jimh111 when were discussing it on this post healthunlocked.com/thyroidu...

Venicefan profile image
Venicefan in reply totattybogle

Thanks 😉

Wow! I Came to ask the same you did! Thanks!

shaws profile image
shawsAdministrator

I take T3 only and have done so for several years.

If having a blood test next day I have the earliest a.m. appointment and fast (I can drink water). I then take T3 after test. I always take T3 with one glass of water and wait an hour before I eat.

I follow the method advised by Dr John Lowe, researcher/expert on thyroid hormones/doctor/ and the following is about T3. He was also an Adviser to Thyroiduk.org.uk before his death through an accident.

healthunlocked.com/thyroidu...

My method of taking T3 once daily is when I awake with one glass of water and wait an hour before I eat. I feek well and am symptom-free and energetic.

Food can interfere with the uptake of thyroid hormones.

Stourie profile image
Stourie in reply toshaws

That’s how I do my lio too. Jo xx

Guineapiggy profile image
Guineapiggy in reply toshaws

What do you suggest to do when taking Metavive? I always take it first thing in the morning. When I have a blood test I take my last capsules 24 hours before the test and I always get the earliest appointment at 8.30 am, then take that mornings dose after the blood draw. As Metavive is the whole dried thyroid gland, with undisclosed amounts of thyroid hormones, am I doing this correctly?

Not what you're looking for?

You may also like...

T3 dose day before bloods

Hello, I normally take 25mcg T3 in one sitting in the morning. The day before my latest blood test...

I don't understand

Alternately titled: 'Here we go again'... Just got back some blood results from a test I did...
lau99 profile image

Time before meals/ T3+T4 Blood tests

Hello, For the past 2 months, I've been on T4 Tirsoint Sol 75 + T3 Thybon 10mcg. My recent...
cezary97 profile image

When to take T3 before blood test - advice please.

This week I'll be doing my next Medichecks blood test for TSH, T4 and T3. I do the blood tests at...
Tasker profile image

blood tests for t3 &levo

Hi 👋 I usually take both my 100mcg levo and 10mcg t3 at 6am each morning. I have a blood test at...

Moderation team

See all
Buddy195 profile image
Buddy195Administrator
PurpleNails profile image
PurpleNailsAdministrator
SlowDragon profile image
SlowDragonAdministrator

Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.

Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.