Why gradual matters
A dog's digestive system adapts to what it eats every day, and an abrupt swap - especially from kibble to fresh food, which differs in moisture, fat and fiber profile - is the classic recipe for an upset stomach. The standard guidance, echoed by fresh food brands and veterinary sources alike, is a gradual transition over roughly 7 to 10 days. It isn't complicated, but skipping it is the single most common mistake new fresh-food subscribers make.
The 7-10 day plan
The pattern is simple: start around one-quarter new food mixed with three-quarters old, hold that for a couple of days, then move to half and half, then three-quarters new, then fully switched - advancing a step only when stools stay normal. There's no prize for finishing early. If your dog has a history of a sensitive stomach, stretch each stage longer; two weeks is a perfectly good transition for a dog that needs it.
What's normal and what isn't
Some dogs sail through a transition with no change at all. Others show mild, short-lived effects - slightly softer stools for a day or two at a new stage is common and usually resolves as the gut adjusts.
What isn't normal: persistent diarrhea, vomiting, refusal to eat, lethargy, or symptoms that get worse rather than better as you hold a stage. Those are signals to drop back to the previous ratio - and if they continue, to stop the transition and talk to your vet before pushing on.
Set the switch up to succeed
During the transition, keep the rest of your dog's routine boring: no new treats, no new chews, no table-food experiments - otherwise you can't tell whether the new food or the party is causing trouble. Feed at consistent times, and follow the fresh brand's storage instructions carefully, since fresh food is perishable in a way kibble never was. Finally, dogs with medical conditions, puppies, and seniors deserve a vet conversation before any diet change, not after - that's not a formality, it's how you avoid learning something the hard way.