DOING FIRST BLOOD TESTS SINCE STARTING T4 - NEED ADVICE ABOUT TIMING T4 DOSE

[Redlester]

In a couple of days I am due to do my first set of blood tests [Thriva] since starting T4 medication. I am also on T3.

I take my T3 at 7am and my T4 at bedtime circa 11.30pm. Can anyone advise me when I should take my meds to get accurate blood test results?

Thanks

[SlowDragon Administrator]

How much T3 are you currently taking

For full Thyroid evaluation you need TSH, FT4 and FT3 tested.

Also EXTREMELY important to test vitamin D, folate, ferritin and B12

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)

When on T3, day before test, split dose into three smaller doses roughly equal 8 hour intervals. Taking last dose T3 at roughly 8-12 hours before test

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

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

REMEMBER.....very important....stop taking any supplements that contain biotin a week before ALL BLOOD TESTS as biotin can falsely affect test results - eg vitamin B complex

[Redlester in reply to SlowDragon]

I am testing everything - full thyroid panel and vits/mins

"Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw)."

I normally take my T4 at bedtime - so based on your advice re testing Monday am, which is when I will be doing my test, I should delay Saturday evening dose levothyroxine until Sunday morning then delay Sunday evening dose levothyroxine until after blood test on Monday morning and take Monday evening dose levothyroxine as per normal

"When on T3, day before test, split dose into three smaller doses roughly equal 8 hour intervals. Taking last dose T3 at roughly 8-12 hours before test"

I take my T3 in a single dose early in the morning - I simply plan to take it after the blood test along with the T4 . While I accept that this is the way I will have to do this in order to generate the most accurate blood test results I have never taken both my meds at the same time before and don't know how it will affect me

[SlowDragon Administrator in reply to Redlester]

I take my T3 in a single dose early in the morning - I simply plan to take it after the blood test along with the T4 . While I accept that this is the way I will have to do this in order to generate the most accurate blood test results I have never taken both my meds at the same time before and don't know how it will affect me

Leaving 24 hours between last dose T3 and test will give a false low result

Day before test you should split T3 and take last 1/3rd of T3 at 9pm assuming test is 9am

And you wouldn’t be taking T3 at same time as levothyroxine

[Redlester in reply to SlowDragon]

I would be taking T3 at same time as taking levo. Twice. My normal dosing regimen which works well for me is that I take my T3 at 7am and my T4 at bedtime circa 11.30pm.

If I delay Sat pm levo dose until Sunday morning, then I will be taking taking 50mcg T4 and my full T3 dose of 50mcg at the same time. Then on Monday morning after the test I will be doing the same, taking my delayed Sun pm levo dose of50mcg T4 and my full T3 dose of 50mcg at the same time [and then waiting for an hour to eat anything].

I am concerned about what will happen if I do it this way as I have never taken T4 at that time before.

If I split my T3 dose on Sunday and take one third of it at 9pm the closest I can get to one third is 3/4 of a tablet. My tabs are 25mcg each. I can break them down into halves and quarters.

Does this mean I can take the bulk of my T3 on Sunday morning as usual in a single dose and then top up at 9pm?

[SlowDragon Administrator in reply to Redlester]

Levothyroxine is a storage hormone…perfectly ok to take at same time as T3

I would suggest

Day before test you split T3 as follows

25mcg tablet waking, 12.5mcg at 2pm and 12.5mcg at 9pm

[Redlester in reply to SlowDragon]

I took both the T3 and T4 at same time on Monday am after doing my tests and didn't have a problem - which is good to know.

[Runner25]

When to take t3