40% off first order40% Off Your First Order — applied automatically at checkout

Log in
Tom&Sawyer
Shop
Meet the ExpertsBlog
Build a plan

How to Transition Your Dog or Cat To a New Diet

By Dr. Hannah Godfrey, PhD · November 11, 2021 · Updated February 13, 2026

Are you thinking about changing your dog's or cat's food, and wondering how to change it with minimal digestion issues? In this guide to transitioning your pet's food, you'll learn all you need to know about switching your fur baby's food successfully.

How to Transition

For a smooth transition, slowly increase the amount of new food over the course of seven days.

Tom&Sawyer — How to Transition Your Dog or Cat To a New Diet

Days 1 & 2: Provide 75% of their old food and 25% Tom&Sawyer Days 3 & 4: Provide 50% of their old food and 50% Tom&Sawyer Days 5 & 6: Provide 25% of their old food and 75% Tom&Sawyer Day 7+: If your pet has any trouble adjusting, stay at that transition stage for a few more days

To find the recommended portion amount for your pet, click here to open the Feeding Calculator .

Why Do You Need To Transition?

Introducing a new diet to your pet is an exciting change! But an abrupt change in diet can result in poor digestive health for your dog or cat. Our pets break down food using enzymes, hormones, and other physiological means .

The nutrients that are released fuel your pet with energy, but they also play a huge role in shaping the microbiome in the digestive tract. When we feed our pets the same diet day in and day out, their digestive systems, and the microbiome, become accustomed to it.

When you change your pet’s diet, you’re changing the composition and formulation. Without transitioning the diets, this can essentially shock your pet’s digestive system. This can affect enzyme production and secretion, hormones, and cause dysbiosis of the microbiome. Together, this can result in diarrhea, gas, upset stomach, vomiting, and your pet may refuse to eat the food altogether.

By slowly transitioning your pet to a new food, you allow their digestive system to acclimatize and slowly adjust. This can prevent shocking the system and help your pet's digestive system find a new routine!

Things to Consider

This transitioning regime is a great foundation to use for your pets when switching over to your favourite Tom&Sawyer diet, but of course, every pet is different. You may have to make some adjustments accordingly:

Hydration is key - Provide fresh, clean water for your pet at all times of the day. Water is an important factor for digestion and overall digestive health.

Your dog or cat may need more than seven days to adjust to their new diet. Be patient. You may need to alter this schedule as necessary, such as if your pet has a sensitive stomach or a gastrointestinal disease .

Once your pet is eating 100% of their new diet, it may take another few weeks for them to adjust completely. If you notice ongoing stomach upset, reach out to your pet’s veterinarian for the best next steps.

About the author

Dr. Hannah Godfrey, PhD

Animal Nutritionist · Lead Nutrition Scientist & Technical Advisor

Hannah leads the nutrition science behind every Tom&Sawyer recipe — a PhD animal nutritionist who turns peer-reviewed nutrition into meals portioned to each pet's real needs.

More from the journal

  • Can Dogs Eat Sweet Potatoes? The Powerful Superfood Your Dog Might Already LoveSweet potatoes show up in a lot of high-quality pet nutrition for good reason. Can dogs eat sweet potatoes? Yes, and we'd go further than that. Sweet potatoes are one of the most nutrient-dense, digestible, and well-tolerated whole-food ingredients you can put in a dog's bowl.
  • National Kitten Day: What Early Cat Meals Can Teach Us About Building Better Feeding HabitsNational Kitten Day on July 10 is one of those moments that invites a bigger conversation. It's not only about celebrating how small and determined kittens are. It's about what we choose to feed them from the very start, and what those early choices set in motion.
  • What We See in Summer Bowls: How Hydration Changes the Way Dogs and Cats Eat in JulyJuly is National Pet Hydration Awareness Month, and if you pay close attention to your pet's bowl during the warmer months, something shifts. Dogs get slower about finishing their meals. Cats grow even more selective than usual. These changes aren't random. They reflect how summer heat affects appetite and fluid balance in ways that go well beyond simply needing more water.
Tom&Sawyer
  • Facebook
  • Instagram
  • TikTok
  • YouTube
  • Pinterest
Get started
  • Shop
Why Tom&Sawyer?
  • Our Standards
  • Science & Research
  • Our Story
  • Giving Back
  • Meet the Experts
  • Reviews
Explore
  • Blog
  • FAQ
  • Contact Us
  • Account
Join the pack

Get access to the latest updates in pet health and wellness, exclusive offers, and more!

Tom&Sawyer
  • Facebook
  • Instagram
  • TikTok
  • YouTube
  • Pinterest
Get started
Why Tom&Sawyer?
  • Our Standards
  • Science & Research
  • Our Story
  • Giving Back
  • Meet the Experts
  • Reviews
Explore
  • Blog
  • FAQ
  • Contact Us
  • Account
Join the pack

Get access to the latest updates in pet health and wellness, exclusive offers, and more!

© 2026 All rights reserved.
Shipping & ReturnsTerms of SaleTerms of ServicePrivacy Policy
Build my pet's plan

It may be RUFF , but limit the provision of treats or table scraps during the transition period to allow your pet time to adjust to their new food.

And don't forget to keep us updated on how your doggo or kitty-cat is enjoying their new, chef-inspired gently-cooked meals (photos are encouraged)!

Article written by: Dr. Hannah Godfrey, PhD, Animal Nutritionist