Log in
Thyroid UK
93,748 members107,754 posts

How much T3 with T4?

I am looking for help from the community on T3 and T4 - I am about to start self-medicating with T3 today and was thinking of 25mcg initially a day. What do I reduce my T4 by to work with this? Should I also monitor my heart rate for a few days? 

Any suggestions/advice would be welcome!

Some Details:

My Thyroid was removed 20 years ago.

I am on 125 mcg Levoythyroxine a day

Female - Age 40

Last Blood Results were:

T3 3.2

T4 24.4

TSH 2.2

Also taking Iron, Calcium, B12, Magnesium, Vit D, Zinc supplements daily.

5 Replies

Most would reduce levo by 50 and take 25mcg of T3 to start with. If you want to be a little cautious take 12.5 T3 for two weeks and then increase (if you feel o.k.) to 25mcg with levo.

I would monitor your pulse/temp before you begin so you have a starting point. Then take both several times a day when starting the combination. If your pulse goes to high or your temp is too high you can reduce levo slightly.

1 like


I take 20mcg with my T4 and when starting only took 5mcg am & 5mcg pm to start with.

I noticed massive positive changes almost straight away but suffered a headache (which appears common) for about three days and a feeling of heat in the body..

After one week I increased the dose to 10mcg am & 10mcg pm. If your heart speed up too much just reduce dose. I agree with shaws to reduce T4 dose by 50mcg.

Good luck.

1 like


25mcg is rather too much.  Start with 6.25mcg added to your current 125mcg Levothyroxine to see how you react to it. After a week or two you could take a 2nd 6.25mcg T3 dose bedtime or evening.  I don't think you need to reduce Levothyroxine dose because TSH is high and your FT4 will convert better with the T3 dose/s.  Ideally, you'll retest 6 weeks after being on 12.5mcg T3.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

1 like

I agree with Clutter that you may not need much or any reduction in your T4, at least when you start T3. I've been taking T3 with T4 for about 6 months, and my FT4 dropped immediately. It seems that more is being converted to T3.  I've had 2 blood tests, and each time, my FT4 was mid-range, having previously always been over range.

I tried to drop my T4 as my endo wanted (he wanted me to drop from 125mcg to 75mcg, but this was a disaster). I can only manage about 50mcg less per week.

Initially, I took only 5mcg T3 per day, and I worked up to 25mcg. For about 5 months, I felt no negative symptoms, but now I'm starting to feel over-medicated, and a blood test confirmed that my FT3 was too high. I've recently dropped my T3 to 12.5mcg per day. I have one or two days a week when I take 25mcg less T4 than I used to.

It feels to me as if I needed extra medication to make up for 15 years of under-medication, but that now, my tissues are appropriately filled with the T3 needed, so that I can manage with a lower maintenance dose.

Given that the bulk of the population have their FT3 and FT4 a little over half way through the range, that is where I want mine to be.

I'm afraid the whole thing is about trial and error, and we all need to find what works for our own body.

1 like

25mcg of t3 is quite a dose I would go with 12.5 to start

why are you taking calcium though ...it simply lines the arteries ...you should be taking magnesium (not citrate form ) k2 and boron thatvdirectscdietary calcium into the bones wherevit belongs


You may also like...