What Is The Best Diet For A Cat With Hyperthyroidism?

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One of the most common disorders in middle-aged and older cats is hyperthyroidism, or an overactive thyroid. The thyroid is a gland that sits in the neck in front of the windpipe. It controls the cat’s rate of metabolism, or how fast their body produces energy. Imagine it as the body’s thermostat, turning up the heat when needed.

With hyperthyroidism, the thyroid speeds up the metabolism even though the cat’s body doesn’t need any extra energy. To use the thermostat analogy, it’s like your thermostat cranking up the heat on a sunny July day!

When this happens, your cat’s body goes into overdrive. The most common signs of this are restlessness, excessive hunger, weight loss despite eating all the time and, in some cases, aggression. Cats with hyperthyroidism often also look unkempt, with a coat that is in poor condition.

Great quality nutrition is important for lifelong good health, but it is even more important when it comes to cats with hyperthyroidism. This is because:


  • They may struggle to stay at a healthy weight and maintain muscle mass. To get the maximum nutrition from every bite, their food needs to be highly digestible and made with the best quality ingredients.

  • They are usually older cats. Middle-aged and older cats tend to have other health issues, such as kidney disease, so their food may need to have controlled levels of protein, minerals and other nutrients to accommodate this. The protein in their food should also come from very high-quality sources.

Ensure that you are feeding a high-quality, complete and balanced food that is suitable for the lifestage of your cat. If your cat has other health issues as well, your vet may recommend a dietetic food to help with the other medical issues. Bear in mind that your hyperthyroid cat will need to eat a higher ration than normal, and almost certainly more than the feeding guide says for their weight. You may be able to feed ad lib if your cat is hungry all the time but losing weight. Alternatively, you can give 4-6 meals a day to ensure they are getting enough to eat. Timer feeders are very useful for this if you are out and about for long periods of time.

Food as a treatment option for cat hyperthyroidism

Cats with an overactive thyroid gland are at risk of malnourishment, high blood pressure, retinal damage and organ damage, such as heart disease, so you should always try to control the problem. There are several treatment options available, including medication, surgery, radioactive iodine and a special dietetic food  - all with their own pros and cons. 

You may be surprised to see that food is a treatment option, but there is a specific dietetic food to control hyperthyroidism. As well as being highly digestible, complete and balanced, it contains reduced levels of iodine. The thyroid gland needs iodine to function, so lowering the levels can slow down the overproduction of the thyroid hormone, resolving your cat’s symptoms after a few weeks. However, the food doesn’t fix the underlying thyroid problem, so your cat will need to stay on the food for life. Your vet can discuss the options and help you to choose the best one for your cat’s lifestyle, their other medical conditions, and your finances.

In summary

If your cat has been diagnosed with hyperthyroidism, ask your vet about treatment options and whether the food your cat is currently on is ideal. Don’t forget to increase their rations until their weight is stabilised and the thyroid is under control. Consider food as a treatment option and ask your vet about dietetic food if you feel it would be a good fit for your cat. Please remember, though, that you should never change your cat to a dietetic diet without discussing it with your vet first.

Reviewed by Dr. Hein Meyer, DVM, PhD, Dipl-ECVIM-CA