Thyroid UK
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Starting T3

Just looking for a bit of reassurance please. Just before Xmas, my endo agreed to prescribe me 20mg t3, alongside 50 levothyroxine but warned me that I might feel worse, get side effects etc. Because of this, I've been to scared to try the new meds yet, but I finally took them today.

I suppose I'm just interested in hearing if people have felt better on t3 and if they had any side affects? I was taking 100,125 levothyroxine on alternate days, but I feel rubbish, can't lose weight easily and instantly feel achy and wiped out with exhaustion. It took some convincing for the endo to let me try t3, so I'm really hoping it will help.

10 Replies

Cut the T3 into 1/4 sizes using a stanley knife.

Only use 5 mcg amounts. Try the first one and see how it goes that day. Look for any signs of an uplift in energy / better thinking. If it happens great. Try stick with 5mcg per day for the next week. If nothing happens try another 5mcg 5h's later.

Eventually you may be taking 4 x 5mcg per day, but it is always better to start low and see how it all goes.

If you take a full 20mcg tablet it can be too much for the adrenals to handle and so you actually go hypo. Too much T3 for me makes me tired and hypo.

The body makes 1-2 mcg T3 per hour, so small doses replicate what the body does more closely.

The most T3 per day i could handle was 55mcg. anymore and i was hypo.

1 like

Actually, I've just realised I'm only on 10, so half the dose of 20. I got told to just cut it in half with a pill cutter and take that and the levothyroxine together first thing.


Do what ever you like, but the best people to ask are the thyroid patients. The docs know very little.

I have found from my experience small doses work much better than bigger ones. I think it is the inability of the adrenals to handle the higher power from a lot of T3. Smaller doses they cope fine with.

It is all about trial and error, so you have to jump in and just go for it.

What works for me may not work for you. You may need super doses of T3 e.g. over 100mcgs. I don't know. But you always start LOW and build up.


Tiredchick, 10mcg T3 is equivalent to 30mcg Levothyroxine. The Levothyroxine dose reduction to 50mcg is excessive in my opinion. It's usual to reduce Levothyroxine dose by 25mcg for every 10mcg T3 added IF optimally medicated on Levothyroxine.

If you post your recent thyroid results with ranges (figures in brackets after results) members will advise whether you were optimally medicated on 100/125mcg Levothyroxine.

T3 doesn't suit everyone but is beneficial for most people. Any adverse effects will usually resolve with a week or two. If not, stop T3 and resume 100/125 Levothyroxine. T3 will be out of your system about 3.5 days after last dose.


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.


I am sure you will find a difference and I really don't understand why they try to frighten patients with information which is truly incorrect.

I suffered terribly on levo and as soon as 10mcg of T3 was added I felt so much better. Now I am on T3 only and haven't looked back and feel well.

I accidentally took double dose yesterday. one in the morning and I took another dose at bedtime, instead of what I usually take (I was in a deep conversation) but even the double dose didn't cause any effect most probably because the gap of about 10 hours. Don't be afraid, it is very calming I found.

I usually only take one whole dose early a.m.


I'm worried he's lowered my dose of thyroxine too much now. I though 10mcg of t3 was the equivalent of 50 thyroxine, so if it's only about 30 and I've got an extra 50, I'm well under what I was taking before. I've just had a blood test this morn before taking the new meds, do will see what that comes back as.


Hi Tiredchick, I've been on t3 only for about 15 years now, I was allergic to thyroxine. I gradually introduced it to my body by a quarter a tablet in the morning for a month. I did this routine in increments of a quarter a tablet per month until I was up to the recommendation of my endocrinologist. My personal opinion of doing it this way gave my poor body time to adjust.

My situation was of course different to yours as I'd been without supplementation for many years. Believe you me at first I was petrified of trying it due to the previous anaphylaxis on thyroxine. Gradually I started feel more my 'old' self.

I'm not medically qualified to advise you of course but go by what your medical team advise and of course what your body tells you. There are people far better qualified to advise on this forum than me but thought you might like to hear my story.

All the best.


I recently started to add T3 to my T4. My endo wanted me to drop from 125mcg T4 to 75mcg T4 in order to take 20mcg T3. As I was scared of the possible side effects I'd been told about, I tried to do that. But I couldn't even get down to 100mcg without going downhill fast.

I changed the doses lots of times over 4 months before ending up on 112.5mcg T4 about half the week, and 125 on some days (depending on my activity level), along with 25mcg T3 every day (half before breakfast, and half before bed).

It is clear to me that I needed the T3, and I had absolutely no negative effects from the T3 for this reason. I am still improving - getting rid of symptoms I've had for 16 years - since starting T4 after a thyroidectomy.

I had no idea in the past that my ever-growing list of health problems was associated with poor conversion, and therefore being hypothyroid, despite having T4 over range.

I think it's a case of trial and error (the way they used to do it), looking out for symptons - good or bad - and making small changes. I kept track of heart rate, temperature and blood pressure, especially at the outset with the T3, and for a week before my endo appointment in January. That way, I could claim that it was always "evidence-based" - but based on what happens to me, rather than some dodgy theoretical model.

Good luck!


I agree with taking a reduced dose to begin with. My endo told me to go straight in with 50mcg of Levo and 20mcg of T3 taken in two doses later in the day than the Levo. I felt very wired that first night, and found it hard to sleep. If I order my own supply I will definitely take it slower. My GP is ignoring the letter from the endo saying I need it, so I've been back on Levo only since late November.


Hi following on from my last post, I've found out my blood test results which were taken just before starting on the t3. Tsh was 0.14, t4 16 and t3 was 4.9. I'm rubbish at interpreting them, but I was feeling rubbish and really struggling to lose weight on this dose eg 125mg, then 100 levothyroxine on alternate days.

I've now been on the 10mcg of t3 with 50mg of levothyroxine for a week and I'm absolutely shattered. I feel like I should be on a higher does of t3 or levothyroxine? What do other people think please?

Not due to see the Consultant for another 6 weeks.


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