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

[Recon]

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!

[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 in reply to Lalatoot]

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 in reply to Recon]

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 in reply to tattybogle]

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

[Venicefan in reply to tattybogle]

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

[tattybogle in reply to Venicefan]

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 in reply to tattybogle]

Thanks 😉

[Hidden]

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

[shaws]

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 in reply to shaws]

That’s how I do my lio too. Jo xx

[Guineapiggy in reply to shaws]

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?