Thyroid UK
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Hashimotos - Weight Loss

I was diagnosed with an underactive thyroid 7 years ago & about a year ago was told I had Hashimotos. Had been on 125 mcg of Levothyroxine for most of that time, about six months ago this was reduced to 100mcg after blood test.

Over the past year I'd had intermittent diarrhoea & soft stools, plus I've been losing weight. Could this be connected to my Hashimotos? Has anyone else experienced weight loss with Hashimotos?

5 Replies

Welcome to the forum, Bigglywiggly.

I gained 13kg at what was probably the onset of Hashimoto's although I felt well. A couple of years later I was very unwell and lost 13kg in 10 months. I suspected Graves, and GP concurred, but bloods showed normal although TPOab was elevated.

I had a thyroidectomy and post RAI I started Levothyroxine (T4) and lost another 7kg. I also had frequent diarrhoea between 4-7 times a day. Each time I stopped T4 diarrhoea improved and I gained 2.5kg which fell off when I restarted T4. I wasn't able to tolerate T4 only but adding Liothyronine (T3) calmed the effects of T4. My weight is still low and I'm hoping rib sticking winter fare will improve it.

It may be an idea to have a coeliac blood screen, ferritin, vitamin D, B12 and folate tested to rule out deficiencies as you may not be absorbing nutrients with frequent diarrhoea. Gluten-free diet helps many Hashi's sufferers to manage gut issues and antibodies but don't start it until after the coeliac screen if you intend having one.


Hello Clutter & thanks for the response. Its interesting reading your experience, I have been tested twice for Coeliac & negative both times. My GP has referred me for a colonoscopy, dismissing that it could be related to my Thyroid. Last TSH test was normal but I've decided to request my full test results from the past couple of years to see if there's anything else odd with the blood results. I don't feel particularly unwell, but do have spells of tiredness, feeling achy, irritable, sometimes palpitations & anxiety...all things which I've gotten used to over the years to the extent I'm not sure what being 'normal' feels like to be honest. The irritability, palpitations & anxiety have been more prevalent over the past six months or so. I also tend to get nasal congestion & post nasal drip & clearing my throat after certain foods like bread & dairy so I do wonder if I have some king of sensitivity to them. At the moment I'm trying to eat more often to stabilise my weight.


Bigglywiggly, It may be worth getting a private FT4 and FT3 test if your GP won't do it to see whether you're converting well.

Coeliac tests aren't very accurate and false negative/positives aren't uncommon so it may be worth trying g-f for 3 months to see whether it improves things.


Thanks. Yes, I'll definitely look into pursuing the FT4 & FT3 tests.


I would have the coeliac blood test first anti TTG as you need to be eating gluten. I was eating gluten although not a lot at blood tests and had positive antibodies, Dr told me to go gf and wait for a letter for endoscopy which I did. Went for endoscopy after only eating gluten again for 2 weeks (worse 2 weeks ever lost 8 lb) and endoscopy inconclusive. I was fuming as it was then 12 months before gastro saw me and refused to retest. I have a strong family history of coeliac and my sister has just been diagnosed too. Luckily I do see the dietitian and she is convinced it is but labeled me latent coeliac. But I know one thing......I will never eat it again the tiniest bit makes me ill for days. Sorry also have autoimmune Thyroid. Also at the the time of testing my ferritin was 10, B12 103 and VitD 25, which were all pretty low. So important to get all checked first.


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