When to test t3?

[Fmljkl]

How long should you wait after changing your t3 dose to check blood levels?

[Lalatoot]

6 to 8 weeks. It takes time for all the knock on effects to settle

[Fmljkl in reply to Lalatoot]

It’s shorter than that for t3.

[Lalatoot in reply to Fmljkl]

No. FT3 levels might change quicker but the other levels will take longer to change. so if you are looking at the whole picture you need to wait 6 - 8 weeks. For example say the increase in your Ft3 level causes your Ft4 level to be reduced as it can do. Your Ft4 level might then become too low for you but this will only be confirmed by bloods when it has had time to settle.

[Fmljkl in reply to Lalatoot]

Ok got it! We reduced my t3 and I’m basically a sloth now with muscle aches. Was hoping I could get it done sooner.

[Lalatoot in reply to Fmljkl]

It is a complicated system of feedback loops. Because you have reduced lio T3 then your Ft3 level should reduce; your Ft4 level may rise as T3 tends to reduce Ft4 level; your Tsh may rise or may not in the longer term. It has taken me 2 years of adjusting doses of lio and levo slowly to get to doses I am currently happy with.

[Fmljkl in reply to Lalatoot]

Oh I thought reducing t3 would reduce t4. My doc mentioned we'd likely need to increase t4 following the t3 reduction.