Switch your dog's food gradually over about two weeks. Start with a small amount of the new food on its own, then mix it in with the old and slowly raise the new share until the old is gone. The PDSA advises a gradual change to prevent problems, and warns against sudden swaps unless your vet has told you to make one.
Below you'll find a day-by-day plan, advice for puppies, seniors and fussy eaters, what to do if your dog's tummy protests, and an honest look at the "7-7-7 rule" you may have seen online.
TL;DR
- Take 10 to 14 days to change your dog's food, not a day or two.
- Days 1 to 3: offer a little new food separately. Days 4 to 10: mix it in and raise the new share. Days 10 to 14: phase out the old food.
- Sudden changes commonly cause diarrhoea and excessive wind, and can put some dogs off their food.
- Puppies, seniors and dogs with health conditions need a chat with your vet before any change.
- Call your vet if symptoms are severe, include blood or vomiting, or last beyond 24 hours.
Table of Contents
- Why you shouldn't switch dog food overnight
- When it makes sense to change your dog's food
- Before you start: choose the new food carefully
- The step-by-step plan: switching over 10 to 14 days
- What about the "7-7-7 rule"?
- Transitioning puppies
- Transitioning senior dogs and dogs with health needs
- Fussy eaters, small breeds and big dogs
- Signs the switch is going too fast
- What to do if your dog has an upset stomach
- Making the transition easier when life is busy
- A quick checklist
- FAQ
- Sources
Why you shouldn't switch dog food overnight
A dog's gut gets used to the food it eats every day. Swap that food for something different in one go and the digestive system has no time to adjust. The PDSA lists diarrhoea and excessive wind as common symptoms after a sudden change of food. It also says sudden changes can cause tummy upsets or food refusal.
The good news is that a slow, planned switch is easy, costs nothing and takes little effort. You only need a little patience, a measuring scoop and a few minutes each day.
When it makes sense to change your dog's food
People switch for plenty of good reasons:
- Life stage. Your puppy is growing up, or your adult dog is entering their senior years. The BVA says food should be complete and designed for the dog's life stage.
- Size. Small, medium and large breeds have different needs, and many foods are made with that in mind.
- Weight. A dog that is gaining weight may need a different food and different portions. The BVA and other veterinary bodies say weight management should be gradual and guided by a vet.
- Preference or availability. Your dog has gone off their food, or your usual brand is hard to get.
- A vet's recommendation. Your vet may advise a particular diet for a health condition.
If your dog has allergies, a medical condition or a prescribed diet, talk to your vet before you change anything. The BVA stresses speaking to your veterinary team first in these cases. If your vet gives you a different timetable from the one below, follow your vet's.
Before you start: choose the new food carefully
A smooth transition starts with a sensible choice of food.
- Pick a complete food for your dog's life stage. Puppy, adult and senior foods differ, and so do foods for small and large breeds.
- Buy from a reputable source. The BVA advises researching diets and choosing reputable companies with safety checks and the right standards in place. It notes that around 90% of UK brands follow FEDIAF guidelines and are UK Pet Food members.
- Be wary of home-made or raw-only plans. The BVA warns that feeding only raw meat or a home-cooked diet can lead to nutritional deficiencies or infections such as Salmonella and Campylobacter.
- Buy enough for the whole switch. You'll be feeding two foods side by side for up to two weeks, so check you have both in the cupboard.
- Check the feeding guide. Work out the daily amount from the packaging of the new food, because it may differ from the old one.
If you'd like to compare options, browse our dog food range and pick by life stage and size.
The step-by-step plan: switching over 10 to 14 days
This schedule follows the PDSA's guidance. The PDSA gives day ranges rather than exact percentages, so the amounts in the table are a practical way of following it, not an official formula.
| Days | What to feed | A practical way to do it |
|---|---|---|
| 1 to 3 | Small amounts of the new food, offered separately | Keep the normal meal as it is. Put a spoonful or two of the new food in a separate bowl or as a small side portion. |
| 4 to 10 | New food mixed with the old, with the new share gradually increasing | Start with about a quarter new to three quarters old. Move to half and half, then three quarters new, as your dog's stools stay normal. |
| 10 to 14 | Phase out the old food | Move to the new food only, once your dog has eaten the mix consistently for at least a week. |
Some tips to make it work:
- Keep the total daily amount the same. You are swapping proportions, not adding extra. Check the new packaging if the calorie content is different.
- Stick to your routine. Feed at the same times each day, in the same place.
- Measure. A kitchen scale or a marked scoop keeps the ratios honest.
- Hold steady if needed. If stools go soft, stay at the current step for a day or two before moving on. If they stay loose, speak to your vet.
- Keep treats simple. Avoid trying a new chew, a new treat and a new food all in the same week, or you won't know what caused a problem.
A sample week for a medium-sized adult dog
Say your dog eats 300g a day in two meals. You could do something like this (the quantities are only an illustration, so always check the feeding guide on your food):
- Days 1 to 3: 150g old food at each meal, plus a small handful of the new food in a separate bowl.
- Days 4 to 6: about 225g old and 75g new across the day.
- Days 7 to 9: about 150g old and 150g new.
- Days 10 to 12: about 75g old and 225g new.
- Days 13 to 14: all new food.
A slower schedule is perfectly fine for a sensitive dog. A quicker one is not the better choice unless your vet says so.
What about the "7-7-7 rule"?
You may have seen a "7-7-7 rule" for dogs. As far as we can tell, it is an informal rule of thumb shared by pet websites, usually describing a switch in stages of about a week each, and it is not a standard set out by the PDSA or the BVA. Different sites describe it differently, so we'd rather not treat it as a rule.
The UK veterinary charity guidance is simpler: introduce the new food separately, mix it in, increase the new share, and finish within roughly two weeks. Some food manufacturers suggest shorter or longer timetables for their own products, so it's worth reading the label on your new food too. If your dog is sensitive, going slower than any timetable is sensible.
Transitioning puppies
Puppies have delicate tummies. The PDSA notes that puppies are prone to upset stomachs when their diet changes suddenly.
If you've just brought a puppy home, don't change their food straight away. The PDSA recommends giving them a few weeks to settle in before starting a 7 to 14 day transition. Keep feeding what the breeder or rescue was using, and ask for a few days' worth to take home.
When the time comes, keep the new food a puppy-specific one. Our range includes options such as Aflora Puppy Chicken with Turkey and Aflora Puppy Salmon with Haddock. For small training rewards that suit little mouths, there are Lily's Kitchen Puppy Chicken & Salmon Nibbles. Our Puppy Essentials collection covers bowls, beds and more for the early weeks.
Your vet will tell you when to move on to adult food, which depends on breed and size.
Transitioning senior dogs and dogs with health needs
Older dogs often have more sensitive digestion, and may have conditions that affect what they should eat. Check with your vet before moving a senior dog to a new diet. The PDSA says veterinary advice is essential if the dog is very young, very old or has other health issues when they have an upset stomach, and the same caution is sensible before a switch.
If your vet is happy for you to move to a senior food, you could look at Aflora Senior Turkey Grain Free Dog Food and take the slower end of the timetable.
For weight management, don't just cut portions. Ask your vet to set a plan, as the veterinary bodies say this should be done gradually with veterinary guidance so nutritional needs are still met.
Fussy eaters, small breeds and big dogs
Fussy eaters. Keep the new food in a small separate bowl at first so your dog can investigate it. Don't add lots of tasty extras to tempt them, or you'll create a habit that is hard to break. If your dog refuses food altogether for more than a day, ring your vet.
Small breeds. Small dogs eat small amounts, so the mix can be hard to measure. Use a kitchen scale or a teaspoon rather than guessing. Options in our range include Aflora Small Breed Chicken with Sweet Potato and Royal Canin Mini Adult wet food.
Large breeds. Big dogs eat plenty, so a mistake is costly in mess as well as discomfort. Take the full two weeks. We stock Aflora Large Breed Salmon & Trout for them.
Changing protein. If you're simply moving between flavours, you still need to go gradually. Our Aflora range includes chicken, lamb and Angus beef recipes.
Signs the switch is going too fast
Watch for these during the transition:
- Loose stools or diarrhoea
- Excessive wind
- Leaving food in the bowl, or refusing it
- Unusual tiredness
If you spot soft stools, step back to the previous ratio for a couple of days, then try again more slowly.
What to do if your dog has an upset stomach
Most cases are mild. The PDSA says most pets with diarrhoea caused by a food change recover within one to three days.
For a dog that is otherwise well with diarrhoea lasting under 24 hours, the PDSA says you may try a 24-hour fast followed by small, frequent, bland meals. Always give plenty of fresh water. This approach is not for puppies, elderly dogs or dogs with another illness. For those dogs, call your vet first.
Phone your vet straight away if:
- the symptoms are severe
- there is blood in the stool or your dog is vomiting
- it goes on beyond 24 hours
- your dog is very young, very old or has another health problem
Our view: a familiar routine makes the switch easier
Most food-switching problems come down to rushing and guesswork. When we look after dogs, the things that help most are a steady routine, accurate portions and someone paying attention to how the dog is actually doing, such as appetite, stools and energy.
That is how we work at Roper and Paws. Our caregivers build a personal relationship with each pet, so a familiar face notices the small changes. Our app lets you follow your dog's care and activity, so if you're away from home during a food switch, you stay in touch with how things are going.
We also stock a dog food range across life stages and sizes, so you can pick a food that fits your dog and take the transition at the pace your vet and your dog need.
Steen
Making the transition easier when life is busy
A two-week switch means two weeks of careful meals. If you work long hours or are away, it helps to have someone consistent who knows the plan. If you live in Bromley or Lewisham, we offer dog walking, pet sitting and everyday care, so a trusted carer can follow your feeding schedule while you're out. Write down the ratio for each day and leave a pre-measured set of portions.
When you're ready to pick a new food, visit our online dog food collection. For walkies and feeding-time kit, take a look at our dog walking essentials and treats and chews.
A quick checklist
- Check with your vet if your dog is a puppy, a senior or has health needs.
- Choose a complete food for your dog's life stage and size.
- Wait a few weeks after bringing a puppy home before switching.
- Offer small amounts of new food separately on days 1 to 3.
- Mix and raise the new share across days 4 to 10.
- Phase out the old food over days 10 to 14.
- Keep treats and extras the same during the switch.
- Watch stools, appetite and energy, and slow down if anything changes.
FAQ
Is it necessary to transition dog food gradually?
Yes. The PDSA advises changing a dog's food gradually, and cautions that sudden changes can cause tummy upsets or food refusal. A gradual switch gives the gut time to adjust. The exception is when your vet tells you to change quickly.
How long does it take to transition a dog to new food?
The PDSA advises a couple of weeks, with its guidance running from days 1 to 14. Puppies get 7 to 14 days after they've settled in. Sensitive dogs can take longer.
What is the best way to mix old and new dog food?
Start by offering a little new food separately, then mix it with the old food. Gradually raise the new share while lowering the old, as the PDSA advises. Finish with the new food only once your dog has eaten the mix well for at least a week.
What should I do if my dog gets diarrhoea after changing food?
Most food-change diarrhoea clears within one to three days. If your dog is otherwise well and it has lasted under 24 hours, the PDSA says a 24-hour fast and then small bland meals can be tried. Call your vet if there is blood or vomiting, if it lasts more than 24 hours, or if your dog is very young, old or unwell.
Sources
- Your dog's diet, PDSA
- Diarrhoea after a change of food, PDSA
- Dog diarrhoea, PDSA
- Eat well. Play more. Puppy leaflet, PDSA
- What should I feed my dog?, BVA
- Policy position on obesity, BVA and partners
- Is it safe to feed my dog a plant-based diet?, BVA
Recommended
- Aflora Senior Turkey Grain Free Dog Food
- Aflora Small Breed Chicken with Sweet Potato Grain Free Dog Food
- Aflora Puppy Chicken with Turkey Grain Free Puppy Food
- Aflora Lamb Grain Free Dog Food
Made with BabyLoveGrowth to get recommended by Gemini
Disclaimer
The information published on the Roper & Paws blog is provided for general information and educational purposes only. While we aim to provide accurate, helpful and up-to-date advice, we cannot guarantee that all information is complete or suitable for every pet.
Articles covering dog health, nutrition, behaviour, training and safety are not a substitute for professional veterinary advice or guidance from a suitably qualified professional. Always consult your veterinarian if you have