T3 swap or Levo combo

Hi All,

I need advise on T3. I have been advised to start T3 by my doctor as my FT3 levels are low (see blood test results below). I am currently on Levo 75mcg. My question is - shall I start taking the T3 together with Levo (do I reduce Levo?) or swap to T3 only? Has anyone done it and have any experiences? My doc says that if I wanted to keep both I would have to monitor my Reverse T3, which may be quite expensive. I'm petrified of going completely T3 only. Any comments appreciated!

TSH - 0.66 (0.35-4.94)

FT3 - 2.5 (2.63-5.7)

FT4 - 13.8 (9.01-19.05)

6 Replies

Your FT4 is also very low, so no need to reduce your dose.

Your doctor, of course, is talking through his hat!! You would only need to monitor your rT3 if your FT4 were right up the top of the range. Were yours is, I doubt there's much danger of excess rT3. And, even if there were, what would he do about it? :)

Still, I'm impressed by a doctor that recommends taking T3, and has actually heard of rT3! Well done, him! :)

Thank you greygoose. Is excess RT3 dangerous, if so in what way? I was thinking to carry on with Levo at 75mcg and then add 5mcg T3 a day to see how it goes, then increase to 10mcg. Would I need to check my thyroid levels monthly after starting T3? Is it worth to just do a one off RT3 test?

No, it isn't dangerous at all. Just no point in taking more levo than you need. I think your plan is good. Leave your levo at 75 mcg, add in 5 mcg, hold for two weeks, and then increase by 5 mcg. Continue that way until you're on 20 mcg, then hold for six weeks and retest.

I really don't think there's much benefit in testing for rT3. It's a very expensive test. If it's high at the moment, it would just mean you have some sort of infection - you're not on a starvation diet, are you? Because that would certainly raise it! But, it wouldn't be raised due to your levo, because your FT4 is below mid-range.


Your doctor should have increased Levothyroxine dose which would have raised FT4 and FT3. I doubt it would raise FT3 sufficiently though so adding some T3 is a good idea. I would start with adding a quarter of a 25mcg tablet (6.25mcg) which can be taken with your Levothyroxine dose. If you tolerate it okay after two weeks you could add a second 6.25mcg dose later in the day or at bedtime. Hold at 75mcg Levothyroxine + 12.5mcg T3 for 6-8 weeks and retest before increasing further. TSH is likely to be suppressed and FT4 may drop but FT3 will rise. FT3 should remain within range. I agree with GreyGoose that it seems unlikely rT3 will be come high because you add T3.

To be fair I am underweight so that's probably why he didn't want to increase my Levo. I will see if I can convince him to do what you suggest. What worrying signs should I be looking out for to make sure I'm not overmedicated? Shall I not test every 4 weeks to start with?


Weight is irrelevant in dosing. You are not going to be overmedicated by adding 6.25mcg - 12.5mcg T3 to 75mcg Levothyroxine. It is premature to test at 4 weeks. 6-8 weeks is plenty of time.

Symptoms of overmedication are hand tremors, moist palms, anxiety, racing heart, palpitations, sweating, irritation, insomnia and diarrhoea.

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