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Home > Cats > How To Make a Cat With Hyperthyroidism Gain Weight (5 Tips)

How To Make a Cat With Hyperthyroidism Gain Weight (5 Tips)

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Dr. Paola Cuevas

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Hyperthyroidism is a common condition found in older cats and less commonly in middle age cats. It affects around 10% of felines over 10 years old, with less than 6% of all cases occurring in cats under the age of 6.

The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces thyroid hormones that regulate metabolism. Benign masses or enlargement of the thyroid gland can cause hyperthyroidism.

If larger amounts of thyroid hormones circulate in the body, they can increase metabolism to dangerous levels and cause damage to organs. Weight loss and muscle wastage are classic signs of hyperthyroidism.

Diet is an integral part of treatment for your cat, alongside medication or surgery, but knowing how to look after your hyperthyroid cat’s weight will improve its overall quality of life. Read on to discover five great tips to help your hyperthyroid cat gain and maintain weight.


The 5 Tips On How To Make a Cat With Hyperthyroidism Gain Weight

1. Diagnosis and Treatment to Manage the Disease

If you suspect your cat has hyperthyroidism, the best and most effective thing you can do to help them gain weight and be healthy is to get them diagnosed and treated at the vet. Treatment is key to continuing health and usually comprises either life-long medication, radioactive iodine therapy, or surgery, all of which are effective and will significantly increase your cat’s quality of life.

Anti-thyroid medication usually comes in tablet or liquid form and is taken twice daily. This medication helps to regulate the amount of thyroid hormone in your cat’s body and put it back into balance, but medication must be adhered to and is often adjusted in the first months of treatment.

For more severe cases of hyperthyroidism, veterinarians can perform a surgical removal of the thyroid gland. Surgery is usually very effective, but there are risks involved with anesthesia and the surgery and recovery itself. Both methods will help your cat get well, regain and maintain lost weight, and improve its quality of life and general condition.

cat in vet clinic
Image Credit; Andy Gin, Shutterstock
  • Medication is relatively inexpensive (compared to surgery) and effective
  • Surgery is usually very effective and a permanent solution
  • Easiest and most effective way to help your cat regain and maintain weight
  • Strict adherence to medication routine is needed
  • May have to have additional tests and dosage changes of medication at the beginning of treatment
  • Surgery comes with anesthesia and recovery risks and can be expensive

2. Prescription Diets

Recent advances in veterinary nutrition have created a therapeutic diet to treat and improve the symptoms of hyperthyroidism in cats. These diets can be used on their own or alongside medication or other treatment, but a strict diet with only the therapeutic food has to be followed, and no other food is to be given (including treats).

The diet uses limited amounts of iodine to help to control thyroid function, but other treatments may be more effective. Despite this, these diets can provide all the nutrition and calories your cat needs when recovering from hyperthyroidism and gaining weight.

  • Easy to administer
  • Cat likely to eat it and continue treatment
  • Strict adherence to diet is needed with no variations
  • It may not be as effective as other methods of treatment

3. Radioactive Iodine Therapy

Radioactive iodine therapy is the best choice for cats with hyperthyroidism. Most cats treated with radioactive iodine have normal hormone levels within fifteen days of treatment and 95% are cured 3 months after the treatment.

This treatment is only permitted at facilities with a license to use radioisotopes. Radioactive iodine is injected into the cat and absorbed by the thyroid. The emitted radiation destroys the abnormal thyroid tissue without damaging other tissues.

After treatment, the cat has to remain hospitalized and isolated for 3- 5 days, until its radiation level is reduced to acceptable limits.

  • Effective
  • Safe
  • Cures the disease
  • Only performed at licensed facilities
  • Expensive

4. Tempt Them to Eat

It can be difficult to coax cats to eat when they don’t have an appetite and are unwell. However, inappetence isn’t usually a symptom of hyperthyroidism in cats since they are typically much more hungry than usual.

However, kidney disease often occurs alongside hyperthyroidism in older cats, and while the two conditions aren’t linked, kidney disease is also prevalent among elderly cats. Cats can lose their appetite and drop even more weight if that is the case.

Offering smaller portions of your cat’s food more often can help them to eat, as it’s less intimidating than a whole bowl. Warming their food (particularly wet food) or adding a small amount of warm water can also release aromas that will tempt your cat to eat.

siamese cat sniffing a treat
Image Credit: Lemalisa, Shutterstock
  • Inexpensive
  • It can help them feel better quickly
  • Various options to try
  • Not suitable for all cats or cats on a special diet

5. Increase Calorie Intake

It may seem obvious, but increasing the number of calories your cat is eating can be trickier than you think. Increasing the amount of energy your cat gets from its food is an effective way to help your cat gain weight and can also help cats that aren’t eating that much to gain weight. Check any diet changes with your vet before going ahead, but kitten food is an excellent choice once this is done.

Kitten food is calorie-dense and often soft, which is excellent for elderly cats (especially those with dental disease). This can give your cat more calories per mouthful than other foods, helping increase its caloric intake and gain weight.

  • Lots of choices for fussy cats
  • Good for cats with dental disease
  • Inexpensive
  • Not suitable for cats on a special diet

You can also use our cat calorie calculator as a useful tool to help your pet here:

The exact amount of calories an individual animal needs to maintain a healthy weight is variable and influenced by many factors including genetics, age, breed, and activity level. This tool is meant to be used only as a guideline for healthy individuals and does not substitute veterinary advice 


Frequently Asked Questions

Why Do Cats With Hyperthyroidism Lose Weight?

Hyperthyroidism speeds up the metabolism in the body. Metabolism is how the body creates energy from calories (from food and drink), and the faster metabolism is, the quicker calories and energy will be used up.

Weight loss in cats with hyperthyroidism is caused by this lightened metabolism, meaning your poor cat can’t gain weight because they’re burning up calories too fast. Their body will then use up fat stores for energy, despite many hyperthyroid cats being hungrier and eating more. However, with treatment, the metabolism will slow down, and your cat will begin to gain weight.

How Can I Help My Hyperthyroid Cat Get Better?

Hyperthyroidism progresses in stages if not treated, but treatment usually stops the progression in its tracks and improves symptoms significantly (sometimes permanently with surgery to remove the thyroid). The prognosis for hyperthyroidism is excellent, but treatment must be adhered to, and owners must take care to monitor their cat’s symptoms. Many hyperthyroid cats also suffer from kidney disease so it is very important that your cat’s diet is advised by a veterinarian.

The best thing you can do to help your cat get better is to follow the treatment precisely as your vet prescribes and give them lots of TLC. With your care and veterinary treatments, most cats will fully recover and regain their weight with no problems.

What is the Best Food to Feed a Cat With Hyperthyroidism?

Depending on the treatment your vet advises, if a prescription diet is recommended, it’s the best food to feed them. If not (and if your vet gives the go-ahead to change your cat’s diet), a diet high in calories with little iodine is the best option.

Wet food is ideal, as it promotes good water intake to keep your cat hydrated and can be calorie and nutrient-dense (such as kitten food).



It can be worrying for owners to hear their cat has hyperthyroid issues, but luckily there are ways to help them recover and maintain any weight they’ve lost due to the disease. With your vet’s approval, changing to a high-calorie food such as kitten food can give your cat more energy and help them put on weight, and they can be tempted to eat it by warming it up.

Treatment of the problem is the best way to help your cat gain weight, however, and is the most reliable and effective way to not only fatten them up but help them be healthy and feel better.

Featured Image Credit: udeenmajid, Shutterstock

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