Thyroid UK
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T3. Need a little advice

Hello, I've just joined and have a query you might be able to help with?

I have an under-active thyroid and currently take 100mg of thyroxine. Been to clinic today and have been given 20mcgs of T3 for a month as I no longer feel the above is working. Here's the dilemma: do I continue with the levothyroxine on top of the T3 or knock the levo on the head and just take the T3. In my haste I forgot to ask...... Any suggestions gratefully received.....

6 Replies

You can replace your levo with the 20mcg of T3 if you wish.

I had to reduce my dose of levo by 50mcg and add 10mcg of T3.

If you decide to do the above, see how it goes for about six weeks and have a new blood test. If you still feel you need an increase I would reduce another 50mcg of levo and take the remaining 10mcg.

20mcg is equivalent to 100mcg levo. It is the active hormone and below is a link re T3 for information.

I hope you find a great improvement


For every 20 mcg of t3 you are supposed to drop by approx 50 or 100 of. T4 to stop you going hyper..... But as itS not working it probably won't make much difference.

If I was you I would just take the 20 of t3 in a split dose... Half in the morning and half later on....., some people would have you split the tablet in 4 but I always found half morning then half at night worked for me.....

If it works for you you will feel a little better within a few hours of taking it..... The British national formulary says start t3 at 10 or 20 and go up to 60 if you need to,

We.l done for getting the clinic to trial you on it!

1 like

Thank you shaws and galathea. I feel relieved to have found the site and joined.

I will take the advice given gladly and update my posts.

I am due for a blood test around 6 weeks time so that ties in nicely.

One last question, do I take them together? (T4/T3)


You can take them together if you wish or split them. Stay away from calcium, iron supplements at the same time as they block the hormone when taken close together.

Keep in mind that your thyroxine has a half life of about two weeks so will be in your system for a while even if you stop taking ANY. Do you think you will take half or 50 mcg and add in your T3.? T3 has a half life of about 12 to 24 hours but works quickly so if you drop have your thyroxine and add 20 mcg of T3, you might feel a little rush when the T3 kicks in but otherwise you shouldn't feel side effects because it should be equal to what you are taking in your thyroxine alone. In eight weeks you should be able to fully decide whether it is helping you (and I think it will).


Definitely split them up. Take one first thing and one after lunch or any time up to an hour before tea. They act fast (1-2 hrs) and last 5-8 hrs depending on your body chemistry, activity etc. It is important to keep the times consistent as your other body cycles slowly adjust to fit. If I take mine an hour late, I do not recover much that day! I am on 3 x 20mcg per day (6.45am/12/5pm). Hope this helps.


Brilliant, I will try this approach. Thanks x


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