When to test on T4 and T3?

[Meno56]

Hi all,

Mid Sept '22 I started to add in 6.25mcg T3 self sourced to my previous 125mcg Levo NHS prescribed (alternating 100/150mcg) daily. This was because previous results have shown poor conversion from T4 to T3, with high T4, low TSH.

Prior to this on 125mcgT4 alone, I made an effort to improve Vit D (75nmol/L range 13-150) and Ferritin (83.6ug/L range 13-150) following advice on this forum. My B12 was high as I had been taking B12 supplement, which I have since stopped and now just taking Thorne Basic B supp daily. My TSH was measured at 0.18mU/L (range 0.27-4.2) Free T3 4.3pmol/L (range 3.1-6.8) and T4 20.8pmol/L (range 12-22) I didn't have any particular symptoms, but had put on weight and felt sluggish, but was concerned about high T4 levels and poor conversion.

End Sept '22 I increased to 12.5mcg T3 and reduced to 100mcg T4. I felt well and noticed reduction in bloating on arms and body, with normal BP and heartrate. I take T3 int he morning and T4 last thing at night.

This week 16 Jan '23 I've increased to 25mcg T3/100mcg T4 and am also feeling well. No signs of overmedication.

I would like to ask, when during the day should I schedule a blood test now that I'm taking T3 as well? I'd like to make sure I'm within range for T3 and check T4 and TSH.

Many thanks for any advice.

[SlowDragon Administrator]

Test thyroid levels early morning, ideally just before 9am and last dose levothyroxine 24 hours before test

Day before test split T3 into 3 smaller doses spread through the day. Waking, mid afternoon and last dose approx 8-12 hours before test

Taking almost any dose of T3 will lower/suppress TSH

You may then have to fight GP to keep current levothyroxine dose prescribed

Have you had thyroid antibodies tested

Presumably you have autoimmune thyroid disease also called Hashimoto’s

[Meno56 in reply to SlowDragon]

Hi SlowDragon thanks for that.

When I was diagnosed I didn't have any antibody testing, but have had 2 Medichecks tests in Sep 21 and Sep 22 for which both Thyroglobulin and Thyroid Peroxidase appeared within range 12.9/13 (range <115) and 27.50/17 IU/mL (range <34) respectively. I don't seem to have any other autoimmune symptoms/issues - have no problem with gluten. I've been ok on LEvo alone, just perhaps not as good as I could be. I'm not sure I have Hashis - I think my thyroid just packed up after childbirth! Consultant at the time suggested viral inection!!