Poorly Controlled Feline Hyperthyroidism

My 16 year old cat Tiffy was diagnosed with a high thyroid level of over 200 last year and was prescribed vivalta. The levels differ at different blood tests. Lowest 74. Now taking 20mg daily. Recent test over 100. Very worried.


I understand your concern. It is very important for animals and people to have a normal thyroid level because thyroid hormone has such an important role in our bodies.

I do not recognize the medication that you mention. In the US, we most commonly use methimazole and I understand that in other countries, carbimazole may be more common. Those are definitely the drugs of choice when treating hyperthyroidism.

Fluctuation in thyroid level in cats on medication is common and that is why regular blood tests are so important. It is also important, especially in your case where the levels have a wide fluctuation, that kidney function be checked regularly and also blood pressure and heart rate and rhythm.

There are alternatives to medical treatment of hyperthyroidism in cats. They are surgical removal of the thyroid glands or radioactive treatment. Has your vet discussed either of those with you?

Do you have another veterinarian that you can go to for a second opinion? Have you tried any other medications other than the one you mention? How often is the level checked? We check the level every 3 weeks until it is normal and then every 4 months after that.

I hope this has been of some help to you. Feel free to write back.

Good luck,
Dr. Neely

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