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Thyroid UK
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Levothyroxine and excessive thirst

I have been on Levothyroxine for over 2 years. We have steadily increased the does as the sypmtons were not eased. In summer 2016 it was increased to 100micrograms. The symptons of pain/fatigue/depression eased quickly and i was happy on that until at Christmas 2016 i had to reduce it back down to 75 due to being over dosed and having horrible side effects.

However, in November I realised I was drinking extremely excessive amounts and therefore having to get up in the night every hour to use the bathroom. The thirst doesn't go away ever.. and my mouth/throat is so dry I somethings cannot speak.

I have had lots of tests - and we are currently investigating Diabietes Insipidus and possible xerostomia. I am not convinced I have either...

My question is - no one has considered it may have something to do with the levothyroxine... not my GP, nor the consultants. Having read some of the posts on the internet it seems this could be a common problem.

Can anyone advise if they have suffered similar problems when the dose was perhaps to too high. Also, I am now on 75mg (since Christmas) and wondered if dropping it to 50mg (obviously I'd see my Gp 1st) could be a possibility. Do people sometimes find they have to change their prescription often to compensate for other side effects? Is it a possibility that my pain/fatigue might not come back if I reduce again?

4 Replies


If the Levothyroxine dose increase caused your dry mouth surely it would have improved in the 4 months since you reduced dose to 75mcg?

Pain and fatigue are symptoms of undermedication and are likely to resume if you become undermedicated.

My thyroid surgeon recommended BioXtra mouth gel to moisturise my mouth.

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Have you been tested for rheumatic diseases such as sjogren's? You might want to rule them out as a cause for excessively dry mouth.


Until late last year I was also excessively thirsty and consequently I would go to the loo a lot. Sometimes every hour. I would be gasping for water if I got too thirsty and I couldn't leave the house without a water bottle as I'd get into a panic if I didn't have any water with me.

I've been undermedicated for at least the last year. Previously I was on 100mcg but my GP lowered my Levothyroxine to 75mcg. I've now gone back up to 100mcg. My ferritin was also around 19 and once I had an iron infusion my thirst was significantly less. My ferritin also increased to 150.

I do go to the loo a lot but it's not as bad as it was before. I still wake up during the night once or twice. I also find that if I'm stressed it definitely gets worse. I think poor thyroid function and not being adequately medicated is definitely related to excessive thirst, at least in my case.

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I have had a problem with excessive thirst since I’ve been “upped” to 100mcg— it’s horrible -I too have a lot of trips to the potty but I can never ever get enough to drink!! Wish there was a way around it—my Dr has been increasing my medication because my thyroid is still too low!!


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