Routine and everyday care
How to switch your dog’s food gradually (a 7–10 day plan)
Mix the new food in gradually over about a week — Blue Cross suggests 25% new on days one and two, 50% on days three and four, 75% on days five and six and 100% on day seven — and take longer if your dog’s tummy needs it. Change one thing at a time, so start any new supplement separately.
6 min read · Written by the PAWVIVE team. Sources are listed at the end of every guide.
Why a gradual switch matters
Most dogs eat the same food day after day, so a sudden change can be a shock to their gut. PDSA explains that upsets after a change of food tend to happen simply because the gut hasn’t had time to adjust, and that diarrhoea and excess wind are the most common problems after a sudden switch, with tummy pain and vomiting occasionally too. Blue Cross advises changing gradually over a few days, introducing the new food and reducing the old, to minimise the risk of a stomach upset.[3],[1]
PDSA also advises avoiding sudden changes unless your vet has advised one, because they can cause tummy upsets or refusal to eat. If your vet has prescribed a new diet, follow their instructions on how to introduce it.[2]
The 7-day plan
Blue Cross publishes a simple seven-day schedule. The percentages are of your dog’s usual daily amount, split across their normal meals.[1]
| Days | New food | Old food |
|---|---|---|
| Days 1–2 | 25% | 75% |
| Days 3–4 | 50% | 50% |
| Days 5–6 | 75% | 25% |
| Day 7 | 100% | 0% |
Stretching it to 10 days (or more)
Seven days suits many dogs, but there is no single official timescale, and UK and veterinary sources give different ones. Where your dog seems unsettled, holding each stage for an extra day or two turns the seven-day plan into a ten-day one. The Royal Kennel Club suggests allowing 7–10 days when moving a puppy on to adult food, and Cornell’s veterinary college notes that dogs with sensitive stomachs may need a longer, more gradual swap.[8],[5]
| Source | Suggested timescale | Approach |
|---|---|---|
| Cornell University (vet school) | 4 days for most dogs; longer for sensitive stomachs | 75% old / 25% new, then 50/50, then 25% old / 75% new |
| Dogs Trust | A few days to a week | Replace a small amount of current food with new, then increase the proportion |
| Blue Cross | 7 days | 25% → 50% → 75% → 100% new food, in two-day steps |
| Battersea | Over the course of a week | Start with a very small amount of new food, slowly swapping parts of the old |
| Royal Kennel Club | 7–10 days (puppy to adult food) | Gradually more new food and less old each day |
| PDSA | A couple of weeks (around 14 days) | New food in a separate bowl for days 1–3, then mixing, then phasing out the old |
PDSA’s version is worth knowing if your dog is fussy or sensitive. For days 1–3 it suggests giving the regular meal with a small teaspoonful of the new food on a separate plate or bowl, without mixing them. From days 4–10 you mix a very small amount of the new food into the old and slowly increase it. From days 10–14, once your dog has been eating the mix well for at least a week, you phase out the old food. PDSA suggests the same very slow approach, over a couple of weeks, for a new puppy once they have settled in on the breeder’s food.[2]
How to switch your dog’s food gradually
Plan the overlap
Make sure you have enough of the old food to last the whole transition, and pick a week without other big changes to your dog’s routine.
Work out the daily amount
Use the feeding guide on the new food’s packet as a starting point, based on your dog’s weight, and weigh portions so the total stays the same as you change the mix.
Days 1–2: 25% new food
Mix one part new food with three parts old food at each meal.
Days 3–4: half and half
If your dog is eating well and their poo is normal, move to 50% new and 50% old.
Days 5–6: 75% new food
Mix three parts new food with one part old.
Day 7: 100% new food
Feed the new food on its own. If any stage was unsettled, take an extra day or two at that stage before moving on, so the change takes 10 days or more.
Keep everything else steady
Keep mealtimes and treats consistent during the change. If your dog has more treats than usual one day, reduce their food that day to compensate.
Life-stage changes
The most common planned switch is from one life stage to the next. Dogs Trust advises moving to the next life-stage food gradually as your dog gets older. PDSA suggests a dog can move to a senior or mature food at around half their life expectancy — roughly seven years old for small dogs and five for larger dogs — and the Royal Kennel Club’s 7–10 day guide is written for the move from puppy to adult food. Whatever the reason for the change, the same gradual approach applies.[6],[2],[8]
Signs to slow down
- Softer poo than usual, or more wind.
- Leaving food, or picking out one food and ignoring the other.
- Occasional vomiting, or signs of tummy discomfort.
- Your dog seeming less keen on mealtimes than usual.
If you notice signs like these, go back to the last mix your dog was comfortable on and hold there for a few days before trying again. Battersea’s advice is to stop the changes and consult your vet if you notice any issues, and PDSA notes that most pets with diarrhoea from a change in food recover in 1–3 days.[7],[3]
When to call the vet
PDSA advises contacting your vet without delay if, after a food change, your dog has:[3]
- Diarrhoea for more than a few days.
- Diarrhoea that comes and goes for 2 weeks or more.
- Diarrhoea and they are very young or very old.
- Diarrhoea along with other health issues.
- Diarrhoea while taking medication, especially anti-inflammatories.
Source [3]
For diarrhoea in general, PDSA’s advice is to contact your vet if it has gone on for more than 24 hours, or straight away if there is blood or mucus, severe or constant watery diarrhoea, reduced appetite, a painful tummy, or your dog seems unwell in themselves. The Royal Kennel Club gives similar advice for puppies changing food: contact your vet if upsets become severe or last longer than a day or two. And contact your vet immediately if you think your dog has eaten something that could harm them.[4],[8],[3]
Introduce a supplement separately
Battersea recommends making food changes slowly and not making too many changes to your dog’s routine at once. The same principle applies to supplements: if you change food and start a supplement in the same week and your dog’s tummy is unsettled, you won’t know which change was responsible.[7]
- Finish the food change first, and give your dog a little time on the new food once it is complete.
- Then start the supplement on its own, following its feeding guide, and watch how your dog gets on.
- If your dog is already settled on a supplement, keep giving it as normal through a food change, so only one thing is new.
- If your dog is under veterinary supervision, ask your vet before starting any supplement.
DIGEST+ is a complementary feed — an addition to your dog’s complete diet, not a replacement for it. Its chicken-flavour tablets can be eaten directly or crushed into food, and the number per day depends on your dog’s weight; the dose calculator works it out. The label advises that it is not recommended for pregnant or lactating dogs, or suitable for puppies under 12 weeks.
Questions people ask
How long should it take to switch dog food?
Most UK advice suggests around a week. Blue Cross gives a seven-day plan, the Royal Kennel Club suggests 7 to 10 days when moving a puppy to adult food, and PDSA suggests a couple of weeks. Dogs with sensitive stomachs may need longer.
What ratio of old to new food should I use?
Blue Cross suggests 25% new food and 75% old for days one and two, 50% of each for days three and four, 75% new and 25% old for days five and six, and 100% new food on day seven.
What if my dog gets an upset tummy while changing food?
Go back to the last mix your dog was comfortable with and slow down. Contact your vet if diarrhoea lasts more than a few days, comes and goes for two weeks or more, contains blood, or your dog is very young, very old, on medication or seems unwell.
Can I switch dog food straight away?
It is best not to, unless your vet has advised it. A sudden change can cause tummy upsets or refusal to eat because your dog’s gut hasn’t had time to adjust.
Should I start a supplement at the same time as a new food?
It is better to change one thing at a time. Complete the food change first, then introduce the supplement on its own, so you can see how your dog responds to each.
Work out your exact supply
The calculator on the product page takes your dog’s weight band and how many dogs you have, then shows the daily dose, how long a bottle lasts and a sensible refill rhythm.
Sources
- Feeding your dog — Blue Cross. Checked 2026-10-15.
- Your dog’s diet — PDSA. Checked 2026-10-15.
- Diarrhoea after a change of food — PDSA. Checked 2026-10-15.
- Diarrhoea in dogs — PDSA. Checked 2026-10-15.
- Re-evaluating your dog’s diet — Cornell University College of Veterinary Medicine (Riney Canine Health Center). Checked 2026-10-15.
- Dog diet and nutrition — Dogs Trust. Checked 2026-10-15.
- How to feed your dog on a budget — Battersea Dogs & Cats Home. Checked 2026-10-15.
- Puppy food to adult food — Royal Kennel Club. Checked 2026-10-15.
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