*This article is for informational purposes only. It’s not intended to be a substitute for professional veterinary advice, diagnosis, or treatment.
The best cat food for hyperthyroidism is rich in species-appropriate protein, low-carbohydrate, and is free from ingredients that contribute to thyroid disease. Iodine management can also help.
Because it’s the only food on the market that’s formulated to reduce hyperthyroidism symptoms, we’ve chosen Hill’s Prescription Diet y/d Thyroid Care as the best cat food for hyperthyroidism.
Our list also includes non-prescription foods that may help your cat feel better before and after medical treatment.
In addition to this Hill’s formula, our list includes four non-prescription products. They won’t treat hyperthyroidism, but they may help your cat feel better before and after medical treatment
Quick Look at Our Top Picks:
Hill’s Prescription Diet Thyroid Care y/d
NomNomNow Chicken Chow Meow
Hill’s Prescription Diet y/d Thyroid Care Original Dry Cat Food
Unless treated with a thyroidectomy, radioiodine treatment, or lifelong drug therapy, hyperthyroidism is usually progressive and may be fatal. Click here to learn more about your treatment options.
Overproduction of thyroid hormones affects the central nervous system, gastrointestinal system, heart, liver, and kidneys. The overactive metabolism burns up fuel faster than your cat can eat it, resulting in muscle wasting and an emaciated cat.
Food is not a cure for hyperthyroidism, but the right diet can help your cat maintain or regain muscle mass and may ensure good health after treatment.
What to Look for in the Best Cat Food?
Hyperthyroid cats need highly-digestible protein.
Hyperthyroid cats have two things working against them when it comes to maintaining muscle mass. First, they have an overactive metabolism, and secondly, most of them are seniors.
New research suggests that seniors have high protein and energy needs—similar to the needs of kittens. When these needs aren’t met, they lose muscle.
Choose foods composed of over 50% calories from protein. The best protein sources are species-appropriate and highly digestible. Your cat requires meat-based food with no high-protein fillers like pea protein, potato protein, wheat gluten, and corn gluten meal.
Choose a diet that’s less than 10% carbohydrate on a dry matter basis.
Hyperthyroidism raises your cat’s blood glucose levels and often leads to insulin resistance and an impaired glucose tolerance. This is a prediabetic state. Even if this doesn’t advance to full diabetes mellitus, hyperthyroid cats are sensitive to sugar and require controlled levels of dietary carbohydrate.
What to Avoid When Feeding a Hyperthyroid Cat
Avoid fish-based foods.
A study in 2000 found that cats who preferred canned cat food in fish or liver and giblets flavors had an increased risk of hyperthyroidism. Fish and other ocean creatures have higher levels of iodine than do other foods. Since iodine is central to thyroid function, this may be part of the connection, but it’s not clear that iodine content is the only problem.
Most fish is contaminated with toxins, including PBDEs.
These fire retardant chemicals were extremely popular in the late 1970s and were used to treat everything from pajamas to curtains. Because they’re known endocrine disruptors, PBDEs were essentially phased out in the United States and European Union during the early 2000’s. That doesn’t mean they’re not still everywhere. These toxins linger in soil, dust, waterways, human bodies, and the ocean — they’re present in cans of fish-based food.
Hyperthyroid cats have higher levels of PBDEs in their bloodstream than do healthy ones.
If feeding canned food, ensure that the can is BPA-free.
Cats who eat canned foods, particularly cans with pop-top lids, have an increased risk thyroid problems. Cat food cans are often coated with an epoxy lining containing BPA. BPA acts as a thyroid receptor antagonist and alters thyroid function.
Don’t feed your cat soy.
When researchers gave 18 healthy adult cats either a soy or soy-free diet for three months, they found that the cats who ate a soy diet ended the study with “significantly higher total thyroxine (T4) and free T4 (fT4) concentrations, but unchanged total triiodothyronine (T3) concentrations.”
The soy-based diet had a small, but significant effect on the amount of thyroid hormone produced by the body.
Should you feed your cat a prescription diet for hyperthyroidism?
Hill’s Prescription Diet y/d is the leading prescription cat food for hyperthyroidism. This food is extremely low in iodine, containing less than 0.32 ppm iodine on a dry matter basis.
In the paper linked above, the writer notes that as of 2011—when the article was written—“all hyperthyroid cats managed with Hill’s Prescription Diet® y/d® Feline as the sole source of nutrition have become and remained euthyroid (having normal thyroid function) as long as the cat had no access to other sources of iodine.”
A low-iodine diet cuts off the supply of iodine, slowing thyroid hormone synthesis. It does not fix an enlarged gland. It does not prevent an adenoma from changing into a carcinoma. It only reduces the symptoms.
How much iodine does a normal cat require?
Given the diversity of iodine concentration in homemade, commercially-available, and wild-caught food, it’s difficult to identify how much iodine cats require.
In 2006, the National Research Council suggested that the dietary iodine requirement for cats was 1.3 ppm. Newer research conducted by Hill’s Pet Nutrition suggests that the requirement may actually be closer to 0.46 ppm.
The 0.32 ppm iodine in the Hill’s diet is low. While it’s currently thought that iodine is only used for thyroid hormone synthesis, we ultimately don’t know how an iodine-restricted diet will affect long-term health.
Because it’s restrictive, not species-appropriate, and isn’t a real cure, think of this diet as a temporary measure or as a last resort for cats who can’t undergo surgery or receive radioiodine.
Top 6 Best Cat Foods for Hyperthyroidism
Because they’re typically lower in carbohydrates, usually contain higher-quality protein, and are more hydrating than dry foods, all of the products on the following list are wet cat foods.
With the exception of the Hill’s prescription diet, these are not treatments for hyperthyroidism. Instead, they contain high levels of highly-digestible protein to maintain and restore lean muscle mass. These foods should accompany curative treatment.
If your cat has any concurrent diseases that demand a special diet, consider those needs first and talk to your veterinarian to find a food that encourages all-around health.
Top Pick: Hill’s Prescription Diet Thyroid Care y/d Feline Canned Review
First 5 Ingredients: Water, Pork Liver, Pork By-Products, Chicken, Corn Flour
While this food is pushed as an alternative to lifelong medication, radioiodine treatment, or a thyroidotomy, it’s not a cure for hyperthyroidism.
It starves the thyroid of fuel, but it doesn’t slow down the progression of a thyroid tumor. The tumor will continue to grow and potentially change into a carcinoma.
A cat on this diet will have to eat it for the rest of their life lest they relapse. They can’t eat any other foods, including therapeutic foods specific to common conditions like CKD, diabetes, or pancreatitis.
Lastly, the food is a high-carbohydrate, low-protein diet. The canned food is about 27% protein, 24% carbohydrate, and 49% fat. This isn’t an ideal calorie distribution for any cat, much less a senior with a propensity to lose muscle mass. Senior cats require high-quality protein to maintain healthy muscle mass, and this diet just doesn’t offer what they need.
- Inhibits excessive thyroid hormone production
- Cats tend to like the taste of the food
- A healthier alternative to the y/d dry food
- A good last resort for cats who can’t undergo other treatments
- Low protein content doesn’t help to maintain muscle mass
- Excessive carbohydrate content
- Only effective if the patient doesn’t eat anything else
Best Non-Prescription Pick: NomNomNow Chicken Chow Meow Review
First 5 Ingredients: Chicken Breast, Chicken Thigh, Chicken Liver, Asparagus, Carrot
This food addresses hyperthyroid cats’ needs in several ways. It’s a relatively calorie-dense food made primarily from chicken muscle meat and organs. These ingredients provide highly-digestible and species-appropriate nourishment to support muscle mass. Despite the inclusion of fruits and vegetables, this food is low in carbohydrates and is safe for insulin-resistant cats.
The food is free of ingredients and additives that might worsen or cause thyroid disease. It’s fish-free and instead of being packed into a potentially BPA-coated can, each serving of NomNomNow cat food comes in a plastic pouch
In addition to its nutritional merits, NomNomNow offers a few unexpected benefits not provided by the average cat food company. The company prepares small batches of human-grade food and ships it to your door. Though NomNomNow won’t customize your cat’s food based on his needs, the company portions out each meal based on your cat’s calorie requirements and special needs.
For further personalized service, NomNomNow welcomes you to send in your cat’s latest bloodwork and medical history, making the company an ally in your cat’s health care.
- Made from highly-digestible protein
- Staffed by nutrition experts
- Meals are portioned out according to your cat’s needs
- Free of ingredients that could trigger hyperthyroidism
- Low in carbohydrates
- Human-grade food
- You can’t get the food without signing up for a subscription
Best Dry: Hill’s Prescription Diet y/d Thyroid Care Original Dry Cat Food
First 5 Ingredients: Corn Gluten Meal, Pork Fat, Whole Grain Corn, Soybean Mill Run, Egg Product
While the wet version of Hill’s y/d is nutritionally preferable, this kibble has all the same hyperthyroidism-appropriate qualities and is equally able to control your cat’s symptoms. In contrast to the wet recipe, it receives marginally better reviews and is—naturally—a more appealing choice for kibble enthusiasts.
The recipe is clinically proven to improve thyroid health in three weeks when it’s the only food a cat eats. In addition to restricted iodine for hyperthyroidism control, the food is formulated with S+OXSHIELD, which Hill’s says can help to prevent urinary crystals.
To address the kidney issues so common among senior cats, the food is relatively low in phosphorus with low sodium. It’s rich in omega-3 fatty acids for inflammation relief.
What We Liked:
- Can help to control the symptoms of hyperthyroidism
- Cats like the way this food tastes
What We Didn’t Like:
- Doesn’t contain any meat
- High carbohydrate content
- Far from a species-appropriate food
- Moisture-depleted dry cat food may contribute to chronic dehydration and poor health
Best for Sensitive Stomach: Instinct by Nature’s Variety Original Grain-Free Real Lamb Recipe Canned Cat Food Review
First 5 Ingredients: Lamb, Lamb Broth, Turkey, Turkey Liver, Ground Flaxseed
Ninety-five percent of this recipe is composed of lamb, turkey, and turkey liver. These are all sources of species-appropriate protein, which will help to support healthy muscle mass and prevent sarcopenia of aging.
That said, this isn’t the most meat-dense food on this list. The recipe includes ground flaxseed, montmorillonite clay, peas, and carrots, none of which are ideal for cats. These inclusions bring the carbohydrate content to around 3% on a dry matter basis.
The company says that while they use a BPA lining in their large cans, their 5.5oz cans are BPA-free.
- High in moisture
- Rich in biologically appropriate animal protein
- Low in carbohydrates
- Free from chemical preservatives, artificial ingredients, and animal byproducts
- Contains some fruit and vegetable ingredients
Budget Pick: Wellness Complete Health Pate Chicken Entreé
First 5 Ingredients: Chicken, Chicken Liver, Turkey, Chicken Broth, Carrots
Caring for a cat with hyperthyroidism gets expensive quickly. If you want to feed your cat well while saving enough money to pay for radioiodine treatment, medication, and vet visits, consider this food from Wellness Complete Health.
It’s not a prescription food and it won’t cure your cat’s hyperthyroidism, but it has all the nutrition to keep your cat feeling his best before and after treatment.
The food is primarily made from muscle-supporting animal protein sources like chicken, chicken liver, and turkey. It doesn’t contain any of our hyperthyroidism no-gos, meaning that it’s free of soy, fish, and high-iodine additives.
Regardless of size, all Wellness cat food cans and cups are BPA-free.
What We Liked:
- One of the best values on the market
- Doesn’t contain soy or other ingredients that might worsen thyroid function
- Rich in nourishing animal protein
- Low in carbohydrate matter
- Packed in BPA-free cans
What We Didn’t Like:
- Uses thickeners heavily
- Contains carrots and several other plant ingredients
Best for Seniors: Feline Natural Chicken & Venison Feast Cat Food
First 5 Ingredients: Chicken, Chicken Heart, Venison Kidney, Venison Liver, Venison Blood
In an article on hyperthyroidism in cats, Pete Wedderburn, DVM mentions the startling results of a recent study. When cats over the age of 10 submitted blood samples for testing, 21% of them had elevated levels of thyroid hormones. With that many seniors experiencing some degree of hyperthyroidism, it’s worth finding food that addresses both thyroid function and senior health.
While this food doesn’t treat hyperthyroidism, it can keep your senior healthy and strong without making hyperthyroidism worse.
It’s a readily-digestible food that features protein-rich animal ingredients like muscle meat, organs, and blood. In addition to these muscle-building ingredients, the food is rich in omega-3 fatty acids for inflammation relief and skin and coat health. Note that the food contains green-lipped mussels, which are ocean creatures high in iodine.
You may want to rotate this food with another seafood-free formula to keep iodine intake minimal.
What We Liked:
- Addresses multiple conditions common among senior cats
- Rich in highly-digestible animal protein for sustained muscle mass
- Low carbohydrate content is ideal for insulin-resistant cats
- Doesn’t contain any thickening gums that might harm your cat
What We Didn’t Like:
- Contains green-lipped mussel, which is high in iodine
- One of the most expensive cat foods on the market
About the author
Mallory Crusta is a writer and adventurecat enthusiast on a mission to make cats’ lives extraordinary. She’s one of the founders of Wildernesscat – a site for happy, healthy, and adventurous cats who are fueled by nature. Visit Wildernesscat for radically natural cat nutrition, home remedies, and lifestyle inspiration.