Thyroid UK
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Carbimazole making me feel unwell

Hi, I am new on here!! But thank you all for you information I have learned a lot.

I was diagnosed with hyperthyroidism 7 months ago and put on carbimazole 20mg and propranolol which helped thendropped to 10 mg. 4 months later I got really ill (all thyroid tests were in normal range) unable to work had brain fog, nausea, exhaustion, pounding heart, lump in my throat, anxiety, panic attacks, dry mouth, constantly weeing in the morning I was told I had acute thyroiditis by my endo who then sent me for a ct scan as she didn’t know why I was so ill!! (I fell out with her and have a new one I didn’t have the ct!) . 3 months on I am getting better I’m still not back to work properly and do not feel back to my old laid back chilled driven self. My new endo has diagnosed me with mild auto immune hyperthyroidism as tsh antibodies are 2.2 (ref range 0-0.4) and serum antibodies at 45 ( ref range -34) my tsh is 2.71 (when I have been well before all this my bloods said tsh 1.16) ft4 now is 18 and ft3 is 5

I am now suffering with nausea and stomach upsets sometimes blurred vision and a little dizziness when in the car (I have never suffered from travel sickness) and generally feeling unwell and not myself. I find I am worse just after taking carbimazole until about 4 hours after. Am I on a too higher dose of carbimazole? Has anyone else been unwell whilst on carbimazole I feel like my symptoms change every week!! I have been taking regular accupuncture and on a gluten free diet which seems to help! I just want my old life back!

22 Replies

Hi sorry your not feeling well. The symptoms sound like hyperactive thyroid. I’ve been taking 40mg of Carbimazole fir 2 weeks and 40g propanol 3 tines a day and I do feel better. However my sleep has now become a problem. How did you feel when you first had the meds?


Hi ya, yes it’s wierd as all my results for the last 6 months out of 7 since diagnosis have been in normal range so unsure why I have been so ill!!

I’m sorry to hear you are suffering with sleeping, I felt fine for the first 3 months on 20mg carb and 40mg propranolol twice a day and went to once a day after first month and I lived a normal life (I think I came off prop after 2 months as I’m a runner and it was effecting my training! I can no longer run as I have no energy) luckily I haven’t really suffered sleep wise only on 2-3 occasions when awoken through racing heart. Im taking propranolol (after speaking with my doc) as and when I need it as it was making me feel worse when taking it twice daily in the early stages, I haven’t used it for 3 months now. I think once the carbimazole kicks in it helps ur heart rate so hopefully it will be the same for you.

I found meditation helps (insight timer app) before and after sleep and I have acupuncture weekly at the moment also having lavender oil on a yoga eye bag helps.

I have completely shut my life down I’m off sick from work and do very little social wise which is not me at all ... I can’t wait to get my old life back.


Hi how long have you been off work? I don’t do much at present. My sleep is on and off and wasn’t a problem when I had other symptoms. I haven’t exercised yet, just squats at home and walking but I want to take it slowly. Propanonol really does help, if my sleep improves I’ll feel better. It’s a difficult disease but i think we need to go easy on ourselves easier said than done sometimes though


How long have you had problems sleeping? I find I have a symptom and it last for a week or so and then I gain another.

I have been off work for 2 and half months (the last sick day I had was 3 years ago with a tooth ache) so not a regular sick note!! I’m on phase return for last week and a bit, at the moment but it’s so hard. I’m trying to ignore it I normally only feel ill 20 mins after taking carbimazole for up to about 4 hrs after so if I could start work at 11.30am would be great!! Haha

Yes same here I try and walk and do yoga once a week but i don’t feel like doing anything else which is unlike me. high cardio isn’t really an option as propranolol doesn’t allow you to it goes against the grain!


Sleeping problems have been last 2 weeks but I’m and off. The horrible night sweats went too but they have come back. The shaky feeling is better


Hi there iam still off work nearly 6 mo ths coming up, exhausted , heart palps, trembles, breathlessness. I too dont have the life i used to either but there is light at the end of the tunnel, i am now hypo but do get your levels tested every 4 to 6 weeks, anything to do with the thyroid is very slow recovery, i did used to feel slightly worse after taking carbi but now im only on 2.5 mgs titration dose as my levels are going more hypo. Keep going and smiling and dont let it beat you.😊


I luv your positivity I’m sorry to hear you have been off work unwell for 6 months I hope your work is being as supportive as mine you don’t need any extra stress with this!

I’m beginning to try and take on a ‘this is not going to take over my life’

mentality but sometimes it makes me feel so nausea I can’t get off the sofa but by mid morning I feel fine ... ha I’m not pregnant! I hope you can get back to work and normal soon 😊


The trouble is when I’m tired I can’t do anything and my mood gets low so it’s s vicious cycle. I’m in bed today because I’m shattered.


Been there done that and still do it.x


On what basis were you diagnosed with a hyperthyroid condition? Please post blood tests and antibodies results here so we can help you interpret them.

Several people on this forum have been treated for hyperthyroidism when their antibodies actually showed they had Hashimotos which is a hypothyroid condition that can cause a flare up increased thyroid hormone temporarily. It's necessary to know which condition you have in order to make effective treatment decisions.

Your Endo should test TSI and TRAB antibodies if he/she thinks you have autoimmune thyroid disease otherwise known as Graves disease. If you don't have these antibodies then you likely have a different thyroid condition, possibly Hashimotos thyroiditis which causes 90% of hypothyroidism. Raised thyroid hormone levels caused by Hashimotos seem to be commonly confused by doctors and mistakenly believed to be hyperthyroidism. This leads to incorrect treatment.


Hi thanks 😊i had tremors which worsened when stressed, heavy muscles when running and feeling sick after running half marathons. I have been given 2 diagnoses of acute thyroiditis and mild auto immune hyperthyroidism.

My results on diagnosis in may this year tsh 0.01 ft4 15

my antibodies were not tested until October on my 2nd endo appt where my tsh anti bodies were 2.2 (0-0.4 ref range) serum anti tpo 45 ( 0-34 ref range) my thyroid test now tsh 2.71 ft4 17 (ref 12-22) And ft3 5 (ref 3.1-6.8) but I haven’t had my anti bodies retested I am ment to have another endo appt end of this month I have come off birth control pill about 3 weeks ago and feel so much better I think it was hindering this condition!


I ha e hashis also and im one of tbe ma y people nanaedake is referring too but my gp and endo both imsist hyper thyroid but what do you do!!


I was on the pill for 20 years and i agree that mine staeted when coming off it.x


If you have TPO antibodies then you have Hashimotos. This is NOT hyperthyroidism although temporary high thyroid hormones may occur. They will naturally settle down.

I would suggest you check what your FT3 and FT4 were when put on Carbimozol. If FT3 and FT4 were in lab range or only slightly raised it would likely have settled down by itself.

You don't give lab range for FT4 but FT4 14. doesn't look high to me when you were diagnosed so why did Endo prescribe carbimazol? if the same FT4 range applied when you were diagnosed as the range you give above then FT4 was actually low. Your FT3 would need to be well over range to diagnose hyperthyroid. It would be unlikely with FT4 so low.

so giving you carbimozol would have worsened symptoms.

Your results now show low FT3 so likely you will have symptoms.

I don't think your Doctors have a clue. They are making you ill. Check all the results and treatments yourself.


Thank you Nanaedake I was diagnosed with hyperthyroidism in may then I got really ill in sept and the doc told me to increase my carbimazole and I got worse in October which explains the antibodies and you saying hashimotos. I was asking to decrease the carb and the endo said no but I did it anyway and 5 weeks later I am starting to feel better I have asked again to decrease but he said no again!! I think I will go private to get a second opinion as I have had so many symptoms and really feel over medicated and it’s making me feel ill!


If you can get a copy of all of your test results from the hospital it might help. To rule out Graves disease which causes hyperthyroidism see the ATA guidelines for which antibodies need testing.

American Thyroid Association on Graves disease

The British Thyroid Association refer to the ATA on their guidelines page, scroll down to find. You can find other guidelines here too.


Thyroid UK have lots of good information about Hashimotos on their website.

Explains thyroitoxicosis and hyperthyroidism

They say, 'Appropriate treatment of thyrotoxicosis requires an accurate diagnosis. For example, thyroidectomy is an appropriate treatment for some forms of thyrotoxicosis and not for others. Additionally, beta blockers may be used in almost all forms of thyrotoxicosis, whereas antithyroid drugs are useful in only some.'


Thank you I will have a read of this 😊

1 like

'Subclinical hyperthyroidism (SH) is most often caused by release of excess thyroid hormone by the gland. This condition is defined as a low or undetectable serum

thyroid-stimulating hormone (TSH) with values within the normal reference range for both triiodothyronine (T3) and free thyroxine (T4) estimates. Both overt and subclinical disease may lead to characteristic signs and symptoms.'

Section 486 of document refers to subclinical hyperthyroidism,

'There are no data for or against treatment of individuals younger

than middle-aged with serum TSH levels between 0.1 and 0.5 mU/L. In patients with symptoms of hyperthyroidism,

a trial of beta-adrenergic blockers may be useful to determine whether symptomatic therapy might suffice.'

' A TSH level between 0.1 and

0.5 mU/L on repeated measurement over a 3–6-month period is considered persistent, effectively ruling out transient thyroiditis as a cause. The thyroid disorder underlying SH with TSH persistently within this range should be diagnosed to avoid treating patients with transient, functional disorders related to acute illness, drugs, and other causes of low TSH.'

SH = subclinical hyperthyroidism


Well Lisa I think I’d feel sick after running a half marathon thyroid or no thyroid issue

1 like

Hi Lisa

I was diagnosed with hyperthyroidism on the 21 of Sep no mention of auto immune by my doc she put me on carbimazole I have been on it since the 21 Sep..17 days I was praying after at least 14 days I would be showing some signs of my symptoms getting better but no I feel just as bad still server shaking,sweating bad,and bad joint pain and now I have new symptoms,,I feel like I have flu,I vomited in my local supermarket trying to get my weekly shop,I felt weak my shaking was uncontrollable,I was sweating so much it was dripping of my noise I felt like fainting my breathing was also bad I was panting trying to get air..I have had my blood test for my white cell count and that was normal but that was 2 weeks ago I'm now wondering if the new symptoms are due to the carbimazole ???? I now can no longer go out without these symptoms affecting me..I'm going back to my docs😡😡😡😡


Hi rimmer, I'm sorry to hear you are not feeling very well.

unfortunately I too had so many side effects on carbimazole, I had loads of tests done and everything was coming back normal. I suffered the same I hated going out because of how I felt and I had to stop work for a bit as the mental and extreme fatigue really got to me (one good thing I discovered online shopping.. I love it.. no more supermarkets!). I felt like my symptoms would change week on week but I did realise my symptoms would get better as I decreased my dose. Make sure your bloods are done regularly (and keep a record of them) I used to do mine every 4/5 weeks then call my endocrinologist and tell him I was decreasing my dose!!

I think it takes 6-8 weeks for carbimazole to start tosettle your thyroid in which case you may find your symptoms will settle. You should find out if your hyperthyroidism is caused through auto immune when you see your endocrinologist.

To help myself I used meditation, yoga made sure I went for a walk every day. I looked at my diet and from advise from this site I went dairy gluten and soya free, I also had acupuncture.

There is another option to carbimazole which you could discuss with your endocrinologist it's called PTU (I was offered it but about 11 months into my treatment🙄 So decided to stay on carbimazole)

You will notice in time symptoms disappearing and there is a light at the end of the tunnel I have been carbimazole free for 3 months now, I'm back to full time work, I just ran my first 10 km race in over a year on Sunday so I can see my life getting back. For me I totally blame carbimazole for my mental side effects as they are very mild-completely gone now. Use this site there is so much knowledge but just do not over google I have given myself bad health anxiety though doing that and you don't know what's true and what's not, 🙄

I wish u well and a speedy recovery


Thank you for your replie

Unfortunately my GP has not referd me to an endo I can remember looking at the prescription my GP was writing out and I recognised the name carbimazole I didn't want to take up the doctors time with trying to remember it so when I got home I looked up my old files from my previous doctors I had an old prescription when my parathiyroid gland went overactive and it was the same meds..that was in 2004 I can remember being really ill on the medication and my old GP took me off them he said I was having bad side affects..he never put me on anything else but this was overactive parathiyroid glands my levels returned to normal but it took me over 12 wks for me to recover I lost over two stone..I'm sure I have the auto immune illness because I have been hospitalised passing blood but no cause was found and about 7 months ago I went deaf in my left ear no cause found..I have been having flare ups for well over 15 months now. I was hoping to have a scan on my kneck given my thiyroid problems but no just meds..I have been in A and E for over 4 hours today as I collapsed in my local wh smiths they called an ambulance the crew said I must go to hospital as my heart rate was over 137 I was shaking uncontrollably as if my whole system was running on speed,,,unfortunately our hospital did not have an endo on call so tomorrow I have to try to make it down to my doctors as he as requested to see me I am hoping he is going to refer me,,if he does not suggest this I defo will.

I'm so glad you have recovered I did gym ball and fitness trampet..but iv been so I'll this past 15 months iv not been able to do any keep fit at all 😢😢😢😢


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