Thyroid UK
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T3 dose increase?

I currently take 150 mcg T4 and 10 mcg T3 daily, the former in the morning and the latter before bed. I've not had any bloodwork done since I upped my T3 dose about 8 weeks ago; my GP pretty much leaves me to get on with it.

However, I am feeling increasingly tired (in a way not seen outside a three-week, two-hours-a-night insomnia bender), and towards the end of the day my pulse drops to about 60 bpm and my temperature to below 36.5 C. I am also having a hard time maintaining, let alone shifting, weight. (This is important for blood glucose control.)

I realise that the knackeredness could be caused by any number of things but I figure that being underdosed on the thyroid meds is the easiest one for me to try to sort out by myself. Would I be better trying to split my 10 mcg into morning and evening 5 mcg doses, sticking with 10 mcg overnight and adding another 5 mcg in the morning, or just upping the single evening dose to 15 mcg?

I do sometimes get hot flushes but they are not constant or even daily; I am being investigated for early menopause so suspect that these might be cause by that rather than overdoing it on the thyroid meds. I certainly don't have any of the other classic overdoing it symptoms like rapid pulse, etc.

Thanks for your help.

13 Replies


I'm new to T3. You mentioned you take small dosages of 10 or 15 mcg of T3. Can you find tablets of that amount or are you splitting 25mcg tablets? I was told those amounts were so small as to make no difference though I do know T3 is considered to be very potent. I am finding all info on T 3 confusing.


Hi Thomas29

I have my T3 prescribed so am getting the standard 20 mcg tablets and splitting them. It's a pain as they have tendency to crumble some but the splitting is broadly in half.


T4 has to be converted into T3 and T3 is the active hormone T4 inactive. Sometimes we cannot convert T4 properly/efficiently so that's why we ask if it's possible to do a Free T3 test. Most labs/GPs refuse if TSH is 'in range'.

T3 otherwise known as liothyronine, doesn't need to be converted and is absorbed into our blood street quickly then goes into our receptor cells and its work then begins and the action of that one dose can last for between 1 to 3 days. People get nervous about T3 but sensible use is fine - in fact I had severe palpitations on levothyroxine and have none with T3. It calmed everything down but best of all it made me well again.

Of course, what suits one person doesn't always suit another but I think at least we should be given an option if one thyroid hormone isn't working.


10mcg of T3 is approx equal to around 30mcg of levo. In this link if you go to page 80 and on the top left-hand column you will see research which has been carried out with regard to different ratios of T4/T3.


Doesn't that rather depend on what the ratio was to begin with before I started adding the T3? FT4 was 19.sth (10-19.8) and FT3 was 3.8 (3.5-5.5). Haven't dropped my dose of T4.


Usually, Endos reduce an amount of T4 when adding T3. But I'm not a scientist and it was scientists who did the various ratios.

I believe liothyronine comes only in 25mcg doses in other countries but not UK lio.

The ratio suggested might well have been due to the patients' well-being on the different ratios.


So I should maybe think about upping to 15 mcg and seeing what happens? That'd be the very conservative 10:1 T4 to T3.


Any decision has to be 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


Be careful of taking too much T3 at night as it can keep you awake -this from my endocrinologist. He's right in my case. I definately wouldn't sleep if I take more than 10mcg. Probably I would add another 5 mcg at lunchtime or first thing in the morning to trial. Your ratio of T3 to T4 is currently low so room for a greater increase in T3.

Blood works can be useful to see what's going might be worth asking for a check on this first thing in the morning of course. Make sure you stop taking your meds for 24 hrs before though.


I sleep soundly on 37.5 mcg of T3 daily. Only take one daily dose a.m. It calmed all my palpitations and body when switched from T4.


I moved it to bedtime as when taken alongside my buproprion (antidepressant - hits up the dopamine receptors) it made me crazy jittery. Sleeping just fine on 10 mcg. A little too well, even.


Do you take it at night then Shaws? We're all so different! Never ceases to amaze me the variations that work. Makes me appreciate how clever our thyroid glands were when they worked!!

My total daily T3 amount is 40mcg but I only take a little at night.


Hose, why not ask your GP for a thyroid test and if FT3 is low, raise T3 dose?


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