T4/T3 ratio

I have managed to get my hands on some T3 to try (25mcg) but I think I have to reduce my Levo when I take it? I am currently on 125mg... and I really want to take it slow! 

My current T3 is   4.5   (3.5-6.5)

                    T4      19.9  (9.5 -21.5)

I have resisted self-medicating for ages but as my GP point blank will have no truck with T3, and almost 4 years on T4 has left me a fat, knackered, brain-fogged, lank-haired old mess, the time has come!

Is there anything else I should know?

Thanks a lot :-)  

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18 Replies

  • Reduce levo by 50mcg and add half 25mcg of T3. (25mcg of T3 equals around 75 to 100 levo). We have to have sufficient T3 in our receptor cells and then its job begins, it saturates the cells and the effect lasts between 1 to 3 days. So you are reducing 50mcg levo for half 25mcg tablet of T3.

    Take note of pulse/temp before you begin just so that you have a starting point. There's no need to be nervous of T3 despite the rumours to try to prevent use. After two weeks you can increase T3, if you wish, by 1/4. Two links:



    (I have no medical qualifications - only my own experience with T4/T3 and NDT).

  • Do ensure your levels of Ferritin - Folate - B12 - VitD are optimal - otherwise it is difficult for the thyroid hormones to metabolise in the body - or  for you to feel well.  T3 is great - I use it - but first build the foundations.....

  • There are several different brands of T3.  You might want to check out the experiences of other people with the brand you are thinking of using.  I used Cynomel for a few years and it was great, now Uni Pharma which is also great, but I hear that Tiromel and the brand prescribed here by the NHS is said to not be very strong in comparison with the other two.  Depending on what you take, may determine your requirements.

    I don't know the strengths but some good soul on here will be able to give details. 

  • Thank you ladies. Marz, my folate/B12 are low so before I try the T3 I am going to take your advice and  make sure that my levels are optimal.

    I did a bit of swotting late last night and found that low levels of both can cause hair loss and tiredness so I need to rule that out. I also read again about people's hair falling out with T3 so it's a wonder I managed to get any sleep!

  • ....don't forget the Ferritin and VitD - they too need to be optimal.  All that research is tiring !!

  • My Ferritin and Vit D are both OK, both over the range that is deemed sufficient anyway! 

  • Probably a good idea to stop supplementing VitD if it is over range.  Ferritin over range can suggest inflammation somewhere in the body....  I have read.

  • Sorry I worded that badly. They just said over a certain amount was OK and I was over so I assume not too high! 

  • You probably need your T3:T4 ratio between 1:4 (NDT) and 1:10, although there are a few people who need less than 1:4.  Just remember the T3 power ratio is 3-4.  So reduce your T4 dose by X micrograms, wait a few days for T4 to decrease, then add in X/3 or X/4 micrograms of T3.  Also keep in mind that Abbott is the company that advertises the T4-only "full replacement" dose is 1.7mcg/kg body weight, so you can use that to decide if the T4-only dose you're on now, might actually be a bit too high.  This is assuming your nutritionals are OK ... have you been on trace minerals like selenium (needed to make the T4->T3 conversion enzymes)?

  • Infomaniac,

    How much T3 do you have?  It's not the sort of think you can take for a week or two and expect results.

    I don't think you need to reduce T4 if you add 6.25mcg-12.5mcg T3 to improve FT3.  You should have a FT3 test in 6-8 weeks after adding 12.5mcg T3 to check FT3 remains within range.


    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.

  • Thanks Clutter. I am going to try and raise my folate/B12 before I try T3 now. I have a month's supply.

  • Infomaniac,

    30 x 25mcg tablets will last long enough to tell whether T3 is helping if you start with 1/4 tablet (6.25mcg) for a week or two before increasing to 12.5mcg which I think is likely to be the most you will need to raise FT3 nearer top of range.  You will need to allow a couple of weeks for shipping when you buy your own.


    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.

  • That's great, thanks a lot Clutter.

  • I didn't drop my T4 at all before adding T3 as my fT3 levels were very low in relation to my fT4 levels. Now taking 150 mcg T4 and 28.75 mcg T3.

  • Did everything work out OK for you then Hose? 

  • Yes, after a fashion. Just got my levels to a place where I felt good but then had to start on HRT. Now back to a good place. Never any danger of being overdosed on fT4 as my problem was conversion not a fundamental problem with T4 itself.

  • I think that's my problem too...but try getting my GP to agree! Glad you've managed to get yourself sorted :-) 

  • I started taking T3 because running was wiping me out more than was reasonable. Read some studies about exercise hammering fT3 reserves and asked my GP whether she'd monitor me if I bought my own T3, explaining my reasons for wanting to do so. She agreed, referred me to an endocrinologist as well. Latter issued script for T3. Now I use half NHS stuff, and make up the rest of the dose with my own.

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