Thyroid UK
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Does fitness / weight affect thyroxine requirements

I finally got on the correct dose of thyroxine earlier in the year and was feeling well enough to return to exercise and healthy eating. I've lost just over half a stone and am much fitter but have noticed my hyperthyroid symptoms seem to be returning. Is it likely the fitness and weight loss are affecting how much thyroxine I will need?

7 Replies


Weight really isn't a factor in dosing. It was sometimes used to calculate starting dose for patients post thyroidectomy but thereafter dose was adjusted according to blood results. If you are feeling hyper on your current dose you could try reducing dose by 12.5mcg daily or 25mcg alternate days and see whether symptoms improve.


I am not a medical professional and this information is not intended to be a substitute for medical advice from your own doctor. Please check with your personal physician before applying any of these suggestions.

1 like

Thank you - will try that and see how I get on.


What sort of hyper symptoms? Some hyper symptoms can also be hypo symptoms, you know. And, as exercising uses up your T3 at an alarming rate, which you cannot easily replace, it would seem to me that they are more likely to be hypo symptoms than hyper.


It's mainly sleep problems. I struggle to fall asleep, but then am wide awake a few hours later and struggle to get back to sleep again.


That sounds more like low cortisol.


Hi octobergirlie67 . I have exactly the same sleep problems you describe. However I am hypo.....never been hyper. Even having got my thyroid blood levels to optimum and supplementing I still often have sleep problems. I think I have just resigned myself to it being my thyroid . Sorry I can't offer any real advice. 🌞


I was concerned this was a typo


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