Thyroid UK
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T3 only - side effects/is it a high dose?

Hi everyone,

After giving Levo a try, and seeing my hormones didn’t go higher at all, my endo prescribed me T3 only and he said I might have conversion problem.

I am on my 6th week and I started T3 with 50 mcg.

Here are the good effects: After 1 week my mood got a lot better, and I am still feeling very positive (as in mood). I am not sure if I started losing weight, but at least I am not gaining now. My hair loss stopped dramatically. An finally, I am not cold all the time anymore. I am so happy with all these.

And the bad effects: I lost my sleep for first 3 weeks. I was living on 2-3 hours of sleep each day. 3 weeks later it it became better but some nights I still can’t sleep. I palpitations for first 3 weeks, then nearly stopped. I just feel it for few seconds maybe twice a week. I got my period in 20 days. It is really early for me. Before T3, it was coming a week or 10 days late. Sometimes it used to miss a month. It was not okay too. I started getting pimples. I have never had acne problems. And I get headaches every 4 days of a week (for last 2 weeks, which is 3 weeks later than the start of T3) just like how I experience 2-3 days prior to my period. My hands shake a little which I am very concerned about. And as a rather less important side effect, I feel like my cellulites are increased. Which makes me really sad as a young, very fit and constantly working out woman.

So after having an early period, my endo asked for blood tests.

- My TSH was VERY low, it used to be between the lower end of the range and mid range.

- My FT4 and T4 was a lot below than the range. They used to be just at or slightly above the low edge of range

- My T3 and FT3 was at the mid range. They were just at or slightly under the low edge of range.

He said he cannot be sure if he should prescribe me T4 and give a lower dose of T3. He told me to wait more. But I wanted to get a second opinion. The other endo said 50 mcg is a very high dose, my ovaries must be working too much. He asked for more blood tests. I am waiting for the results and for the next appointment. Buy I believe in your advices.

Is 50 mcg a high dose? What may be the reasons and possible fixes for the side effects? Stopping or even decreasing the dose of T3 frustrates me. I am in love with this better mood and higher energy T3 brought me. But also, these serious side effects frustrates me for the long term too.

Please excuse my English as I am not a native speaker. And thank you for your advices in advance.

3 Replies

50 mcg is not a high dose per se. But, it was a massive dose to start on! People normally start on 5 mcg and work up slowly to find their sweet spot.

Do you have the actual numbers for your FT3? Result and range. Your TSH is bound to be suppressed on 50 mcg T3, and if you're not taking any T4, your FT4 is obviously going to be low, too. Do you have any labs from when you were on T4 only? I don't think either of those endos you saw had much idea what they were doing!

How much T4 were you taking before changing? The normal procedure is to add T3 to T4, and slowly increase T3 and decrease T4 until you feel comfortable. Of course he doesn't know, now whether he should add in T4. He's doing things the wrong way round. You would have to add in T4 slowly - start with 25 mcg and increase every six weeks if necessary. Do not let him suddenly start you on 100 mcg, or something! :)


The only negative side affect I have had taking a little extra T3 was that it caused my blood pressure (BP) to shoot up. Directly after my total thyroidectomy I was on T3 only and I felt great - but no-one was watching my BP. Yes, I was supposed to be doing that but I was new to all the medical stuff so I never imagined I should have measured my BP. Moving a few years on, when I realized how great optimal T3 makes one feel, I experimented by increasing my thyroid meds with a little T3 - and up went my BP so I had to stop the extra T3.

So that is the side effect I would suggest you keep an eye on.

1 like

I think you should test your acth and cortisol.


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