Thyroid UK
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Carbimazole and weight gain

Hi I've been on carbimazole for 9 months. My original dose was 20mg for the first three months then 10mg for a month, then 5mg for a month. My dose was reduced to quickly so I want back to 20mg. For the past three months I have been on 15mg.

My weight just keeps going up and up. It doesn't seem to matter what i eat or how much exercise I do. Before been diagnosed I weighed 10st albs and now I weigh 12st 12lbs. I hate the way my body looks I want to lose the weight but how 😟

3 Replies

Have you had a recent blood test to check your T4/T3 levels ? It is important that these do not go too low.

I found that reducing refined carbs / sugar helped me to control my weight on Carbimazole.


It's important to get regular blood tests done and to keep a check on your results to see where you feel most well.

When I titrated Carbimazole I had blood tests done at least every 8-12 wks. I found less than 8wks didn't give an accurate result.

How did you feel on 10mg? Personally I would have gone from 20mg to 15mg and got tested at 8 weeks. If still feeling ok then go down to 10mg


I do not have a lot of experience with thyroid problems this way around, all I can say is that it sounds as if you are overmedicated, i.e. the carbimazole is supposed to slow you down, it is pretty obvious that you have been too slowed down if you are piling on weight. What about it you started all over again, take a tiny dose, wait a couple of weeks if you can then see what happens. Then increase your dose in small increments checking your response to each dose very carefully.


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