When should I switch my puppy to adult food?

It depends on breed size, roughly 9 to 12 months for small breeds and up to 18 to 24 months for large breeds. Ask your vet to confirm the right timing.

How do I change my dog's food without upset stomach?

Transition gradually over 7 to 10 days, mixing more new food with less old food each day. A probiotic or sensitive-stomach formula can help if your dog's gut is touchy.

Transitioning Your Puppy to Adult Dog Food

4 min readReviewed by Dr. Jane Mitchell, DVM

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Growing up means a diet change. Here's when to switch to adult food and how to do it without an upset stomach.

Why the switch matters

Puppy food is richer in calories, protein, and minerals to fuel rapid growth. Once growth slows, staying on puppy food can lead to excess weight. Adult formulas match a grown dog's steadier energy needs.

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Timing depends on size

Small and toy breeds often mature by around 9 to 12 months, medium breeds around 12 months, and large or giant breeds not until 18 to 24 months. Switching a big-breed puppy too early can affect healthy bone development. Your vet can confirm the right window for your dog.

Make the change gradual

Transition over about 7 to 10 days, mixing increasing amounts of the new food with decreasing amounts of the old. This gives the gut time to adjust and reduces the chance of diarrhea or vomiting. Slow and steady wins.

Support a smooth transition

If your dog has a sensitive stomach, a gentle formula like [Hill's Science Diet Sensitive Stomach Dog Food](/products/hills-science-diet-sensitive-stomach-dog-food) or a probiotic like [Purina FortiFlora Probiotic Supplement](/products/purina-fortiflora-probiotic-supplement) can help ease the change. Keep meals and routines consistent while you transition.

Watch and adjust

Monitor stool quality, appetite, and energy through the switch. If soft stool or upset persists beyond a few days, slow the transition or check with your vet. Recheck portion sizes on the adult food, since calorie density often differs.

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Frequently asked

When should I switch my puppy to adult food?: It depends on breed size, roughly 9 to 12 months for small breeds and up to 18 to 24 months for large breeds. Ask your vet to confirm the right timing.
How do I change my dog's food without upset stomach?: Transition gradually over 7 to 10 days, mixing more new food with less old food each day. A probiotic or sensitive-stomach formula can help if your dog's gut is touchy.