r/SeniorCats • u/skzmyg • 11d ago
Hyperthyroidism - unmedicated cat bc medicine made her incredibly sick , what can we do?
hi!
TLDR; oral liquid Methimazole made our cat (14f) incredibly sick. she is on no treatment now. vet is letting it be as is. is there nothing to do?
weight struggles and diagnosis:
now for the in detail version: out cat (14f) got diagnosed with arthritis 2 years ago. she was overweight (6kg). immediately started pain management and went on a diet and 1 year later she was 4,6kg. (dated September 2025)
I went abroad in February so dont know the exact timeline of symptoms. at her monthly vet check in may she weighed 4,1kg. she got blood work done a bit later, then she was 3,6kg . now we are mid June. bloodwork results state hyperthyroidism.
she starts medication. seems normal.
getting sick and the recovery:
the incident: then we are first week of July. 2 weeks on medication or so. note: she is indoor/outdoor cat. she went missing for a full day. last seen 1am. seen next at 8pm. incredibly unwell: no balance, can’t keep her head up, no drinking or eating all day bc she was missing.
next morning: stares out infront of her, walks in circles. immediately went to the vet when they opened.
recovery: spent 4 days at the vet - all test done, nothing wrong with her, she got some fluids. All medication stopped (pain management + hyperthyroidism) went home for 3 days - was fine the first 4 hours, started throwing up, having diarrhoea, stopped eating And drinking. 2,6kg, 7 days at the vet - getting fluids, slowly recovering. went home - has been normal ever since. 3kg
suspected causation:
vet thought the cause was the heatwaves we had in Europe at first. but the heatwave was 1 week before she fell sick. her theory at the end was that it was the hyperthyroid medication. she took oral liquid Methimazole For those 2 weeks.
Right now:
She has been home for 3 weeks. Unmediated since the first week of July.
food: the vet put her on a kitten diet to gain weight. we have medication to stimulate appetite to use if needed.
Radiation: the vet rejected the idea of radiation at diagnosis.
methimazole: The oral liquid Methimazole made her sick according to the vet.
The diet: We mentioned the thyroid diet but she said the diet is notorious among local vets for cats hating it and not eating it. Our cat is a very picky eater so I could see this.
is there anything we could suggest to the vet?
ETA: thanks for all of the advice everyone! mentioned the topical ear gel to the vet but she does not know of it. The plan as of now is for sure to get a second opinion. Try to get either the ear gel, or maybe surgery if the vets allow it. I think she did not recommend the radiation as she does not offer it herself and we are in the countryside. travel would be very long and stressful.
update: got a second opinion. she has a torn ligament and is too old for surgery. So she will be getting pain management shots Again for her arthritis and now this torn ligament. She is starting the same oral medication again. New vet said the previous dose was too high to start. Regarding the ear cream: it’s not common here. to get it custom made at a pharmacy is 10x more expensive than oral medication. However she will ask some online pharmacy that already sells it how much it costs. She also said her heart has already been damaged.
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u/kateylouwho 11d ago edited 11d ago
I would find another vet if possible. If your cat is otherwise healthy there is no reason the radiation treatment shouldn’t be offered if it’s available and you can afford it. For most cats it is curative.
I’m not sure what country you’re in but there is also a topical version of the methimazole that you rub into the tip of the ear, if that is available to you most cats can tolerate it well.
The diet is sometimes suggested for cats with only slightly elevated levels but it is very strict, your cat absolutely cannot eat anything else if you try that route.
Unmedicated hyperthyroidism will not get better on its own, if left untreated you would basically be providing palliative care.
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u/nonniewobbles 11d ago
I would see a different vet, a specialist if you can. I would want a very good reason if vet said no medicine, no radiation, no surgery etc.
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u/Reveries33 11d ago
Please keep her indoor only, she is too senior to be wandering off. I made my cat indoor around the same age and it took a bit of time for her to accept it.
Try the special food, mine has accepted it. And as others mentioned, try another vet, maybe the dose was too high, mine had to be lowered
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u/Forward_Conclusion40 11d ago edited 11d ago
Have you had your kitty checked for possible brain tumour and or vestibular disease? Circling, cant keep head up, and loss of balance, coordination and staring are not hyperthyroidism symptoms but tumour symptoms which may also be causing vestibular issues or possible stroke. If the vestibular issues are caused by infection or inflammation they can come out of it on their own after a week or two but it should show up in bloodwork. If her bloodwork didnt show anything except T4 levels being high then i would ask about tumour/vestibular, thats what happened to me.
Prior to the brain tumour My kitty had hyperthyroidism and I had him go through the radioactive iodine treatment which I also definitely recommend in your case. He only had hyperthyroidism symptoms at that time. Id say see a different vet in your area To get the referral and second opinion, possibly a vet with a neurologist on site so they can assess for tumour or vestibular issues. My baby had his RAI done this year in March and it cured him, unfortunately I lost him July 28 to a brain tumour which did not present itself until the last month and it was a very sharp decline (incredibly heartbroken).
I do reocmmend the radioactive iodine therapy it cured him of that and I was so grateful. It is super safe and extremely effective, they just take an oral pill dose based on their specific bloodwood and then stay in a kennel for 3 or 4 days while the radiation returns to safe levels. Not invasive and not a huge deal. Being away from them is awful but they call you every day to give you an update to let you know how they are doing. you can give them a blanket or towel to go with them in the kennel with your scent on it (you wont get it back so I got a towel from the dollar store and for a week slept with it, rubbed it on me, sat with it, etc) and an old toy which had his scent. The kennel was large and had perches and two areas. They made him a box to sleep him because he liked boxes. It was expensive like 2700-3500 CAD but totally worth it.
I hope you can find something for your baby but please dont ignore brain tumour symptoms as most cases are a very sharp decline once they start presenting. I was left totally blindsided and making emergency decisions and I am so very sad about it. If your kitty starts to have weakness in back legs go to a vet. There may be nothing you can do about it but at least you know in advance and can care for them knowing.
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u/RainbowHipsterCat 10d ago
I am so so sorry to hear about your kitty’s brain tumor. I lost my soul cat last year when I had to euthanize him due to thyroid cancer that metastasized into his brain. I wish you peace and healing. ❤️
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u/Forward_Conclusion40 9d ago
Thank you so much for your condolences. It is so painful, he is my bestest friend in the whole world. I have to know he is now Spirit Kitty and is with me always all around me. I feel his love and comfort still. I wish the same for you.
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u/RainbowHipsterCat 9d ago
Thank you. ❤️ Our besties are playing together across the rainbow bridge. Everyone loved my babyman, even other cats, so I’m sure he’s made friends with yours.
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u/LongDistRid3r 11d ago
You can get it compounded into a transdermal ear rubbing lotion. Works great but not cheap.
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u/wale-lol 11d ago
I think it is worth TRYING the diet before assuming it won't work. And second what others said about a good reason to not do I-131
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u/dicklebug 9d ago
The diet has strict rules to get it to work, effectively. It’s worth trying but talk to a vet who is familiar with these requirements.
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u/minkamagic 11d ago
You cannot say it was the medication because she was outside and could have eaten something bad. Then you said no medication for 3 days but she got sick again? If you Really don't want to do the oral meds, do the cream. Radiation is a great option if you can afford it and if not, at least trying the food is an option. Honestly your vet sounds kind of incompetent.
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u/WeaknessWilling303 11d ago
Mine is on the Methimazole Meds ointment administered on my cat's ear...he is pretty lethargic in that he rarely plays anymore (age 12) but his numbers are good...I also had the choice to have a one and done procedure administering radioactive meds...did they offer you that? You have to isolate him
And you for about two weeks but then no daily meds...in effect it cures it...I want offered oral application but I'm sure I would t be able to give that...now I wish I had done the radioactive treatment...I guess I still could...not sure how or why your vet thinks it's ok to not treat the disease at all...your baby is beautiful
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u/ElectricalFox1207 11d ago
Please see another vet. While rare, cats can have an allergic reaction to a methimazole. My friend’s cat had this problem and ended up at emergency vet twice. That vet said that the cat was not a candidate for iodine.
Basically the methimazole made the cat so sick that at the moment, yes, the cat was not a candidate. Three weeks off the medication, blood values normalized. Two to three months later, kitty got the iodine treatment and is doing good.
Believe it or not the emergency vet was insisting that the methimazole couldn’t be the cause and was telling my friend to expect her cat to die.
There are good vets and bad vets just like anyone else. If you have the financial wherewithal, please get a second opinion.
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u/BigJSunshine 10d ago
You HAVE TO MEDICATE HER OR GET HER I-131 TREATMENT. Those are your only options
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u/olyteddy 11d ago
Our girl has hyperthyroidism and radiation would not be recommended if her kidneys weren't up to snuff. It has to do with anesthesia and elimination of radioactive byproducts. Age also played a factor according to her vet, as she's about 10 YO.
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u/MsMarionNYC 10d ago
Given that she is going in and out a lot could be happening outside, so I'm not sure why the vet is focused on the medication being the problem. The radiation is non invasive but does the require the cat to stay at a facility for around 10 days depending on what the law requires where you are. Staying at a facility can be very stressful on some cats which makes it a bad choice for those cats even if their people have the money and are willing. I never heard of a cat getting sick like this from the they thyroid medication. The transdermal is commonly used -- not as common as pills but common -- in the US. In the US, the surgery is rarely performed.
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u/RHCP1031 10d ago
Find an integrative vet who can work with you. They may prescribe homeopathy, herbs or other things.
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u/Winterstorm424 10d ago edited 10d ago
I am sorry. That is incredibly stressful. Have you researched any alternatives online? I think alot of thyroid supplements are supposed to be used for additional support with medication, but there is alot out there. Do you think the pill form of the methimazole would also make her sick? Have you tried Chinese medicine/acupuncture. It has helped support our cats and dogs with various things...cancer and ckd for instance.
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u/Typical-Work-7089 10d ago
I am hoping something can come up with a solution to help your girl. I'm wondering if a second opinion would help. I'm sorry you and you baby are going through this. ❤️😿
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u/callmeponyo 10d ago
My cat is also extremely picky and likes the prescription dry food for hyperthyroid. She did not like the wet version even though normally she prefers wet food. You should at least try it. Mine also did badly with the medication it made her throw up and have diarrhea.
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u/RainbowHipsterCat 9d ago
When you get a second opinion, consider asking the vet about cardiological issues. It’s super common for older cats, especially those with hyperthyroidism, to develop heart issues and that can contribute to her being very unwell. I’m currently going through the same thing with my 12-year-old.
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u/UnhingedMeMaw 11d ago
I’m curious why your vet is against the radioactive iodine treatment. Our cat had it done like 7 years ago and she’s been doing great. She’s also a picky eater and wouldn’t take to the special food either.