Thyroid UK

T3 or T3/T4.Any thoughts?

Afternoon all

I posted a few weeks ago to say thanks for all your help and advice. My lovely Endo has written to me after having bloods taken. My two choices with my treatment are: a) 20mcg of T3 split into two doses per day or b) 20mcg of T3 plus 25mcg of T4. 

My bloods are:

Free thyroxine 16.1 (9.8 -18.8)

TSH 0.06 ( 0.4 - 4.0)

Free T3 7.5 (3.5 - 8.5)

PV 1.73 (1.5 - 1.72)

My question is this.What would be the benefit of taking the T4?It was doing nothing before and I feel great with the T3, so why not just take the T3? Or do I still need the T4 and if so, why?

I would appreciate any thoughts



3 Replies


If you feel good on T3 20mcg I'd stick with it. You can always increase T3 or add in T4 if you feel less good as time goes on or you need increased dose. Your FT4 and FT3 are comfortably in the top 75% of range which we need to feel well.

T4 will increase your storehouse of the inactive hormone FT4 which converts in the liver to the active hormone FT3. T4 has a life of approximately 8 days so you won't experience fluctuations if you miss a dose or two. T3 has a short half life of 8-12 hours so peaks and troughs can be experienced as dose is taken/due.

Some people feel better with T4+T3 combination than either T4 or T3 monotherapy and some can't tolerate synthetics and take NDT.

What is PV?


Thanks for the reply.That makes more sense. I think I am going to try the T3 only and see how it goes. PV is plasma viscosity. Think it shows inflammation in the body.


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