Feeding Your Dog or Cat During Cancer Treatment: A Guide to Nutrition, Appetite, and Comfort

Written by Kelly Gredner RVT, VTS (Nutrition)

Receiving a cancer diagnosis for a beloved pet is a moment that shifts a pet parent's world, bringing a wave of heavy emotions and uncertainty. As our dogs and cats live longer, fuller lives, the reality is that the risk of cancer increases, particularly for those over five years of age.² Yet, amidst the clinical terms and difficult news, there is a path forward rooted in care. While a diagnosis may feel like losing control, nutrition offers an empowering way to reclaim it, serving as a powerful, hopeful tool to support your pet’s strength, comfort, and quality of life through every step of their journey.

What Is Cancer in Dogs and Cats?

Cancer is a complex, multifaceted medical problem with many compounding causes from exposure to carcinogens to genetics. Cancer is also hard to prevent and can happen in any bodily system (skin, oral, spleen, etc).

In a normal state, cells die off and are replaced by new cells on an as needed basis. Sometimes, this process is changed when abnormal or damaged cells multiply instead of healthy ones. These cells can stay and become what we know as tumors, or spread to other parts of the body in a process called metastasis.⁵

In its simplest definition, cancer develops when cells in the body reproduce at an accelerated rate and spread to other areas of the body.⁵

What Signs of Cancer Should You Watch for in Dogs and Cats?

Cancer signs vary because cancer can develop in many different places. The symptoms are generally based upon where the cancer originates, which is why any new physical or behavioral abnormality should be discussed with your veterinarian.

Because of the variety of types of cancers, and places where it develops, the symptoms also vary widely. The symptoms are generally based upon where the cancer originates.

For example, if a dog or cat develops skin cancer, you might see changes in the area like:

• Redness

• Lesions

• Licking the area

• Excess itching

• A visible mass

If it’s oral cancer, they might exhibit:

• Drooling

• Producing a bad odor in the mouth

• Have difficulties chewing

If your pet is exhibiting any abnormalities, either physical or behavioral, have a discussion with your Veterinarian.

How Do Veterinarians Diagnose Cancer in Dogs and Cats?

Diagnosing cancer comes down to what type of cancer it might be and where it may be located. Some tests that might be used are:

• Bloodwork

• Urine testing

• Ultrasounds

• Radiographs (x-rays)

• Biopsies

• CT Scan

What Cancer Treatments Can Affect Appetite and Nutrition?

There is ongoing research into the treatment of cancer in pets. Treatments include:

• Surgery

• Radiation therapy

• Chemotherapy

• Oral medications

Some cities have veterinary oncologists available for referrals. Some places even have full centers dedicated to the treatment and care of pets with cancer. With such advancements, we are seeing more pets experiencing remission, improved survival times and a greater quality of life.⁴

What Is Cancer Cachexia and Why Does It Matter?

In chronic illnesses like cancer, a disorder called cachexia can occur. This is most prevalent in cases of cancer. This condition can cause:²

• Weight loss

• Muscle loss

• Reduced immunity

• Fatigue

• Anemia

• A poor prognosis.

It further weakens the body and is caused by multiple factors like reduced caloric intake, increased bodily inflammation and increased caloric requirement.²

Using food as therapy can help slow progression or, ideally, prevent this altogether.

What Should You Feed a Dog or Cat With Cancer?

The best diet for a pet with cancer is the one they will eat consistently enough to maintain a healthy body weight. There are many theories about cancer diets, but nutrition should stay individualized to the pet, the cancer type, the treatment plan, and any other medical conditions.⁴

It’s common for pet parents to develop a distrust in the food they were originally feeding, worried that it might have been the cause and look to make dramatic or abrupt dietary changes.⁴

Some pet parents even turn to home cooking, which might do more harm than good despite their best intentions. Publicly available recipes through blogs, websites, and social media have been shown to be unbalanced, present the risk of introducing foodborne illness, and/ or to have insufficient instructions to ensure proper nutrition.⁴

Ultimately, the best diet is the one that the pet will eat consistently enough to maintain a healthy body weight. But, there are some things to consider if a pet parent wants to switch their dog or cat's food during this critical time.

Feeding Your Dog During Cancer Treatment: What Should Matter Most?

When feeding a dog during cancer treatment, the main goal is to maintain calorie intake, body weight, and muscle condition while choosing food your dog tolerates well. Appetite, nausea, vomiting, and fat tolerance should all guide the plan.

The type of cancer and treatments can all have effects on appetite and caloric intake. Chemotherapy and radiation can affect the gastrointestinal system causing nausea, anorexia, and vomiting.⁴

It can become a very stressful, ongoing struggle to meet the nutrition needs of one’s pet during this time. Nutrition for a pet with cancer should be personal/individualized as cancer is different in every pet.

Feeding Your Cat During Cancer Treatment: What Should Matter Most?

When feeding a cat during cancer treatment, consistency and appetite support are especially important. Cats can become food-averse or eat less during illness, so palatability, meal frequency, and early veterinary support matter.

The same basic nutrition goals apply to cats: maintain body weight, support muscle, and keep meals appealing enough that the cat continues to eat. Some cats may need more variety, more aromatic food, or smaller, more frequent meals to help support intake during treatment.

Should Pets With Cancer Eat Low-Carbohydrate Food?

Low carbohydrate diets are often discussed for pets with cancer, but the idea that carbohydrates simply “feed cancer” is outdated and not entirely accurate. Tumor cells vary, and different cell types can use protein, fat, and carbohydrates differently.² They are flexible! Which means, it’s a complex issue and there is more research to be done on this.

Here are some basic guidelines when choosing a food for a pet with cancer.¹

Energy for Pets With Cancer: Why Palatability and Calories Matter

Pets with cancer may struggle to eat enough, so food should be palatable and energy dense. A tasty, higher-calorie diet can help improve caloric intake when appetite is reduced.

Goal: Palatable and Energy Dense

A pet’s daily energy requirements may also increase with cancer, making hitting those markers challenging. Fat provides almost twice as many calories compared to carbohydrates and protein (8.5 to 3.5kcal/g) and fat improves flavor!

Fat for Pets With Cancer: When Higher Fat May Help

Fat can help increase calories and flavor, but the right amount depends on the pet’s tolerance level and other conditions. Pets with fat intolerance, pancreatitis, or other medical issues may need a lower-fat approach.

Goal: Fat 25-40% on a dry matter basis or 50-65% metabolizable energy (percentage of calories in the diet)

Looking at fat content itself, this will be based on your pet’s tolerance level and diet availability. Start at the lower end of the spectrum, and gradually increase the fat content, monitoring your pet’s response.

For pets with cancer, they may have an increase in the breakdown of body fat to supply energy to the body, and at the same time, they store less fat. Together this can add to weight loss in these pets.³

Unless your pet has a concurrent fat intolerance, switching to a diet higher in fat than their original one might work in their favor to improve food intake and body weight.

Protein for Dogs and Cats With Cancer: Why Muscle Support Matters

Protein levels should exceed minimum adult maintenance needs because cancer and treatment can contribute to muscle loss. The goal is to support muscle, blood proteins, and gastrointestinal function while considering the pet’s full medical picture.²,³

Goal: Dogs: 30-40% on a dry matter basis or 25-40% ME/calories Cats: 40-50% on a dry matter basis or 35-45% ME/calories

The protein levels in the diet should exceed the minimum daily requirements that the dog or cat needs (adult maintenance levels).²

Because the pet and tumor cells have their own set of protein (amino acid) needs, this might mean feeding a higher protein diet than their usual diet to prevent muscle wasting, low circling blood proteins (hypoalbuminemia), and impaired gastrointestinal function.³

Carbohydrates for Pets With Cancer: Are They Always Bad?

Carbohydrates can still be included in a pet cancer diet. They provide easy-to-use energy and beneficial fiber for gut health, though they may be used in lower amounts or selected carefully depending on the pet’s needs.

Goal: <25% DMB or 20% ME

Though the nutrition focus might be on fat, protein, and calorie intake, carbohydrates can still be included. They can be used in lower amounts than the pet’s usual diet or by being selective on the types of carbohydrates used.

Omega-3 Fatty Acids for Pets With Cancer: What Is the Goal?

Omega-3 fatty acids may be beneficial because chronic inflammation plays a role in cancer. However, the recommendations have not been clearly defined.

Goal: >5% on a dry matter basis, omega 6:3 - 1:1

Changing the ratio of omega 6 fatty acids to omega 3 fatty acids to support the anti-inflammatory effects could help with the chronic inflammation that plays a large role in cancer. The inclusion of EPA and DHA can limit tumor growth.³

But more is not necessarily better! It’s about balance and dosing. Over supplementing with omega 3 fatty acids could lead to decreased platelets and vasoconstriction (reduced blood flow).²

This is more of a concern in our feline friends, and there is overall more research on the effects of omegas in dogs over cats.

Should Pets With Cancer Take Antioxidants or Supplements?

Popular in people, pet parents might want to supplement their pet’s diet with, or look for diets enriched with, antioxidants.

Beta carotene, lutein, selenium, vitamins A, C, E are best used as a preventative measure over feeding them once cancer has developed.

Dr. Hannah Godfrey covers preventative cancer nutrition and wellness tips for dogs in more detail in dog cancer nutrition and health tips.

Although they might be helpful in cancer prevention and in tumor recurrence, antioxidants may reduce the effects of cancer treatments therefore, use of antioxidants and supplements for pets with cancer or undergoing treatment should be discussed with your veterinarians.²

What Should You Avoid Feeding a Dog or Cat With Cancer?

Pets with cancer should avoid risky diet changes, raw food, unbalanced homemade diets, and supplement-heavy approaches unless your veterinarian approves them. The main goal is still complete and balanced nutrition that helps maintain a healthy body weight.

Raw diets might be something that a pet parent considers switching to, but this could be a high risk switch. Pets with cancer can be immunocompromised by disease, treatments or both so therefore more susceptible to infections.²

Another emerging idea is to feed our pets ketogenic diets, or diets that have the majority of calories coming from fat (60-80% ME). There is no research to support this and high fat diets don’t work for all pets, nor are they easily accessible.

Unbalanced diets can come in the form of overfeeding treats, home cooking without supplementation, haphazardly putting together raw diets, tasty toppers meant for supplemental feeding, etc.

One thing to remember is that feeding a complete and balanced diet and eating to maintain a healthy body weight are the main nutritional goals for pets with cancer.

Best Tom&Sawyer Meals for Dogs With Cancer

Any gently-cooked, human grade, complete and balanced Tom&Sawyer meal may be helpful for a dog with cancer if the dog will eat it consistently and tolerate it well. Recipe choice should depend on appetite, fat tolerance, protein needs, and concurrent disease.

Simply put, any of our gently-cooked, human grade, complete and balanced meals may be helpful for your dog! They are high in moisture and super tasty, with an increased digestibility and bioavailability of essential nutrients.

Some meal highlights would be:

Classic Pork Stew

• Most calorie dense meal at 742kcal/pack

• Our highest fat meal at 55% of calories comes from fat

• It’s a low carbohydrate meal at 11% of calories coming from carbohydrates

• Tasty!

Beef&Broccoli* 🍁

• A reduced fat meal for those fat intolerant pups at 25g/1000kcal

• Higher protein at 40% ME or 41% dry matter

• Anti-flammatory ginger root

• Antioxidant goji berries

Fisherman’s Best Friend Supper

• For pups with concurrent kidney disease as has nutritional markers formulated to support kidney and urinary health (sodium, potassium, calcium, magnesium)

• Reduced fat for fat intolerant pups at 19g/1000kcal

• High in omega 3 fatty acids with an omega 6:3 ratio of 1.27:1

• Novel protein for pups with food allergies

• NOTE: High in carbohydrates at 55% ME

Best Tom&Sawyer Meals for Cats With Cancer

For cats with cancer, the best Tom&Sawyer meal is the one your cat will eat consistently and that fits their nutritional needs. Cats may benefit from aromatic, moisture-rich meals and thoughtful rotation when appetite changes.

And for our furry feline friends:

Bento Box* 🍁

• Lowest carbohydrate option at 20% calories from carbohydrates

• Omega 3 fatty acids from salmon

• Highest calorie option at 370kcal/pack

• Anti-inflammatory ginger root

• Aromatic and flavorful

• PLUS a booster of functional and supportive nutrients from our proprietary EHS Blend of chia seeds, fructooligosaccharides (FOS - a prebiotic), marshmallow root, taurine, l-carnitine hcl, astragalus extract polysaccharide, glucosamine hydrochloride, and turmeric

Wild West Kangaroo* 🍁

• Novel protein for kitties that have allergies or sensitivities

• Low carbohydrates at 20% calories coming from carbohydrates

• An omega 6:3 ratio of 0.92:1 for anti-inflammatory support

• Antioxidant cranberries

• PLUS a booster of functional and supportive nutrients from our proprietary EHS Blend of chia seeds, fructooligosaccharides (FOS - a prebiotic), marshmallow root, taurine, l-carnitine hcl, astragalus extract polysaccharide, glucosamine hydrochloride, and turmeric

Feeding Tips for Pets With Cancer

Small feeding changes can help make daily care less stressful. The goal is to keep meals appealing, reduce food aversion, support intake, and catch weight loss early.

Helping a pet through progressive, chronic illness is stressful, and management becomes a part of the daily routine. But small changes in feeding can help!

Make Food More Appealing

• Warming up the meals to enhance the aroma and taste.

• Add variety with safe, appropriate options when possible

Use Meal Rotation

Consider feeding on a rotational basis offering a few different options. This means having up to three meals available to help once they "tire" (or become food averse) of one. If your pet gets bored with one, switch to another and rotate back to keep interest high!

Feed Smaller, Frequent Meals

By offering small, frequent meals you can help your pet to:

• Meet calorie needs

• Maintain digestive health

• Improve appetite

Monitor Weight Closely

• Weigh your pet regularly

• Track changes in weight over time

• Pending the size of your pet, consider purchasing a baby scale to monitor and trend their weight (this works well for cats and small dogs)

This way you can catch weight loss sooner and get them the help they need.

Please note: Feeding tubes can also be discussed as a less stressful and more efficient way for pets to receive medications, fluids, and nutrition. Discuss with your vet if this is an appropriate option for your dog or cat.

Final Thoughts: What Is the Best Way to Feed a Pet With Cancer?

There is no perfect cancer diet for every dog or cat. The best approach is to focus on complete and balanced food, maintain body weight, keep meals appealing, and work with your veterinarian to personalize the plan.

Caring for a pet with cancer can feel overwhelming. But nutrition is one of the most powerful tools you have to support their health during this emotional time.

By focusing on:

• The right nutrients

• Managing their weight

• Keeping meals appealing

You can help your pet stay comfortable and enjoy a better quality of life!

There is no “cancer diet” or perfect way to feed our pets during their time with cancer. If you’re unsure what to feed, talk to your veterinarian. Together, you can build a nutrition plan tailored to your pet's needs.

 * currently available in Canada only

Resources

1. Hand M.S. et al. (eds) (2010). Small Animal Clinical Nutrition 5th ed. Mark Morris Institute.

2. Fascetti, A. J., & Delaney, S. J. (Eds.). (2012). Applied Veterinary Clinical Nutrition. Wiley-Blackwell.

3. Case, L. P., Daristotle, L., Raasch, M., & Hayek, M. (2011). Canine and feline nutrition (third edition). Mosby.

4. Raditic, D., & Gaylord, L. (2021, February). Nutrition for small animal cancer patients. Today's Veterinary Practice. Retrieved July 2026, from todaysveterinarypractice.com.

5. What is cancer? NCI. (n.d.). https://www.cancer.gov/about-cancer/understanding/what-is-cancer