When to Put a Cat to Sleep With Hyperthyroidism? Things to Know!

Written by

Amy Sawy

Veterinarian. DVM


Joseph M. Plummer

Veterinarian, DVM, MVZ

when to put a cat to sleep with hyperthyroidism

It’s sad news that your cat’s got hyperthyroidism, a common disease among middle-aged and older cats. This condition will cause many health problems that impact his lifespan.

Without treatment, hyperthyroidism will become much worse and might lead to fatality. Thus, it’s essential that you get an immediate diagnosis and therapy by the time you’ve realized some unusual symptoms.

Though no one expects the worst result, there’s still a possibility that you question when to put a cat to sleep with hyperthyroidism.

In fact, to make a decision, you need to consider different factors related to the cat’s condition and medication. There’s no need to rush (or panic). The information below will assist you in finding a solution.

When to Put a Cat With Thyroid to Sleep?


After being diagnosed with hyperthyroidism, cats will be put into a series of special treatments. While some will interact well with the care and improve their health gradually, others might find it difficult to maintain a longer life expectancy.

In the latter case, you need to pay more attention to their progress as well as their well-being before deciding whether to euthanize them. Of course, this rough decision should be made after consulting with the veterinarian.

However, don’t make it too fast until it appears that further treatment no longer works and your cat is suffering from much pain.

Here are some crucial aspects that are needed to be discussed before giving your final choice:

1. Age of your cat

Your cat’s age is one of the crucial factors that affect the efficiency of medication.

Older cats with thyroid stand a less chance of surviving, compared to the younger ones. They tend to become more stressed during treatment and might experience further health problems.

2. Your cat’s health condition and comorbidities

Any progress in your cat’s state of life is worth further waiting and hope. However, when it comes to severe pain and declining health, it’s time to think of euthanasia.

Noticing cats’ conditions is a must if you need to know where the treatment takes them. Cats with comorbidities are more prone to fatality after each complicated operation or radiation treatment.

Severe diseases and organism damage like kidney or heart disease are those that make the cure more challenging. In this case, talk to your vet to decide if it’s better to go with euthanasia.

3. Thyroid’s stage

Another factor to consider before euthanizing a cat with hyperthyroidism is your cat’s disease stage. The vet will tell you about his life expectancy after examining whether it’s in the early stage or the late stage of hyperthyroidism.

Apparently, a soonly detected case is more likely to be cured than the last-minute one. The extreme choice will arise when your cat’s condition is the worst and there’s no medication applicable.

The Lifespan of a Cat With Hyperthyroidism

Remember that there’s no fixed scenario for a cat with thyroid. Depending on each cat’s health condition and treatment, his lifespan might vary:

  • With good medical care and treatment (such as the I-131 therapy), your cat might lead a long and healthy life of up to 5 to 6 years.
  • In case hyperthyroidism in cats is left untreated or not cured appropriately, there are just a few months

Early signs and late signs of thyroid disease in cats


It’s crucial that the hyperthyroidism of your cat is diagnosed and cured in time. The sooner you take him to the vet, the more chances of bringing back his good health.

Check out these alarm symptoms so that you’re not missing any single day of his lifespan

Early signs of your cat dying of thyroid disease

  • Increased ravenous but severe weight loss
  • Excessive thirst and urination
  • Vomiting
  • Diarrhea
  • Depression
  • Become aggressive and hyperactive
  • Changes in fur

Symptoms of late-stage hyperthyroidism in cats

  • Increased heart rate and blood pressure
  • Difficulty in breathing
  • Become much weaker
  • Convulsion

Can Hyperthyroidism in Cats Be Treated? How to Treat It?


The good news is that cats with hyperthyroidism can be cured and you might receive a successful result. There will be several tests (blood tests, radiographs, and urinalysis, for instance) and diagnoses before the vet decides the best plan for therapy.

Particularly, there are four options available:

1. Anti-thyroid medical treatment

This method is commonly used to manage the impacts of the thyroid gland, not curing the disease.

There will be some side effects when cats are treated with medication, including fever, anemia, vomiting, depression, and so on.

Antithyroid drugs are often required for cats with high surgical risks in a long-term period. Your cat will be examined periodically to see whether the treatment is effective so that the vet can appropriately alter the dose of medication.

2. Surgical thyroidectomy

Another treatment for hyperthyroidism in cats is to get rid of their thyroid glands. This surgical method will likely lengthen your cat’s life expectancy without needing medication.

When cats have a stable health condition (except for the thyroid), they stand a high chance of successful operation.

However, this treatment is not suggested for cats with comorbidities like kidney, diabetes, or heart disease for so much risk.

3. Radioiodine therapy (I131 treatment)

This effective method will help to cure the thyroid instead of just controlling it in the long term. It’s widely used for bringing good results without causing any side effects or severe risks.

Your cat will be kept in the hospital for a few weeks (about 2 to 3 weeks) during the treatment. Plus, there will be some strict rules to follow after they’re cured to ensure the best safety.

4. A diet for a cat living with hyperthyroidism

Some studies show that a diet with a limited amount of iodine is applicable for cats with thyroid since it reduces the thyroxine that the thyroid gland produces.

However, this is not the optimal choice among others. Though it works with the thyroid, restriction of iodine consumption might cause some negative effects on cats’ overall condition.


Is hyperthyroidism painful in cats?

Untreated hyperthyroidism in cats might cause additional health problems, such as high blood pressure or damage to eyes and brain. It will make them suffer from anguish and pain.

What to feed a cat with hyperthyroidism?

To help reduce the harm of hyperthyroidism, it’s crucial that your cat follow a low-iodine diet. Canned foods that are not mainly produced from grains and vegetables are optimal. Additionally, meat by-products or quality-meat ingredients are also a good choice.


It’s never easy to decide when to put a cat to sleep with hyperthyroidism. Many cat owners agonize over such choices on Reddit, which you can sympathize with. Though this option is harsh, seeing our beloved pets struggling with this disease day-to-day without any hope is more painful.

Examine our information and consult your vet for the most appropriate treatment. We all wish for a successful treatment and that our pets will maintain a healthy life as long as possible. Thus, take it slow and carefully consider all the situations before choosing euthanasia.

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