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My 4-month-old kittens ate adult food. Is it okay? How to transition?

Updated on September 23rd, 2025

Pet's info: Cat | American Shorthair | Male | neutered | 4 lbs

Hi, I'm adopting two 4-month-old kittens tomorrow who are currently living at a foster home. I just learned the foster mom has been feeding them *only* adult cat food for the last 8 weeks! -- both kibble and wet food (Purina kibble and fancy feast wet food). I'm worried about their nutrition and think I should transition them back to kitten food, shouldn't I? Please tell me exactly what to do and the best way to transition them. THANK YOU SO MUCH!!!

3 Answers

Most Helpful Answer

Dr. Melanie, BVSc MS

Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on August 31st, 2023

How lovely of you to take on these kittens! Yes, you are correct they should be on kitten food and should stay on kitten food until they are one year of age. Purina kibble is a great food, just get the kitten version. To switch them to it, mix 75% old food and 25% new food, and feed them that for 3-4 days. After that time period, give them 50% old food and 50% new food mixed together. Again, feed that for 3-4 days. Then mix together 25% old food and 75% new food, and feed for 3-4 days. Finally, then give them 100% new food. This will help slowly transition them to the kitten food. If you see diarrhea at any point, add a little less new food and a little more old food to settle their stomach. Once the diarrhea is gone, continue the transition. I hope this helps!
Vote Icon11Pet Parents found this answer helpful

Related Answers from Veterinarians

  • Answered By Lindsey Edwards MVB, BSc, IVCA

    Veterinarian

    Published on July 27th, 2019

    Adult food is not formulated to meet the exact needs of growing kittens and I recommend they should be on at least 80% kitten food until 6-9months old. If the food is not going out of date I would keep it until they are more mature and maintain on kitten food initially to promote healthy growth and development. Occasionally mixing some in would be ok in moderation

    Vote Icon

    1Pet Parents found this answer helpful

  • Answered By Christie Long, DVM

    Veterinarian, Certified Veterinary Acupuncturist

    Published on September 25th, 2018

    Kitten food is specially formulated for kittens to achieve proper growth and development, and as such, is higher in calories than adult cat foods. Kittens should be fed kitten foods until they reach about 90% of their adult size, which typically occurs around 10-12 months of age. Any time a diet change is made, it should be done so gradually to minimize the risk of developing an upset stomach with vomiting and/or diarrhea. Transition the kitten food and adult food by mixing the foods together over 5-7 days, beginning with 75% old food and 25% new food for a day or two, then 50% old food and 50% new food, and then 25% old food with 75% new food.

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    56Pet Parents found this answer helpful

Smart Picks for Smart Questions

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Hello, any new diet that will be offered should be transitioned gradually. Sudden diet changes may cause a decreased appetite, vomiting or diarrhea. So transition the diet slowly. Make sure that the new food is also for kittens as she needs the additional calories and protein for her growth. Hope this helps and best of luck.
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My kittens prefer wet food. Is feeding adult wet food & kibble okay?
I think the schedule is reasonable and fine to stick with. Try to keep the majority of the kitten’s being the kitten food. That way most of the food intake will support their growth and development. If you have trouble finding food in the store, you might look online as you can often find it for reasonable prices. Ideally the kittens would eat all kitten food until they are about 11 to 12 months old. You could also feed a canned food that is meant for all life stages as this will support growth as well. I hope this is helpful and please feel free to post any additional questions.
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Can 5-week-old rescued kittens eat adult Purina One dry food?
How lovely of you to rescue these kittens! Yes, Purina is a fine brand to feed them, but it does need to be a kitten formulated food to meet their nutritional needs. If you can't find that, I would feed them the wet food until you can get out to find some dry kitten food. I hope this helps :-)
Updated on September 23rd, 2025
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How long does it take to switch young kittens from wet to dry food?
Great question! It should take about two weeks to transition them. Mix together the wet food and the dry food, and over the next two weeks, slowly increase the amount of dry food and decrease the amount of wet food until they are eating the dry food only. I hope this helps :-)
Updated on September 23rd, 2025
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When should my 11-month kitten switch to adult food, same brand?
I recommend switching to adult right at 1 year of age, but if you wanted to make the transition now I think that would be fine. If she seems to be doing well on her current food it's a good idea to stick with the same brand.
Updated on September 23rd, 2025
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My kittens have diarrhea after eating adult cat food. What to do?
Congrats on your kittens but I'm sorry they are sick! It may be the change of diet that is causing this foul stools, and I would take them off that food. An adult cat food is not appropriate for kittens. They need higher amounts of calcium, protein, and calories than adult cats to grow properly, so they need to be on a kitten food. They may be eating voraciously because they are so hungry and their nutritional needs are not being met with the adult cat food. Take them off the adult cat food, and buy kitten food. Start them on a bland diet of boiled white meat chicken (no bones) in small amounts to see if that helps settle their stomach and clears up the diarrhea, and after two days on the bland diet, start adding in the kitten food. You can mix the boiled chicken with the dry or wet food. Over the next week, decrease the amount of chicken and increase the amount of kitten food until they are eating the kitten food only. If the bland diet does not help clear up the diarrhea, they will need to see a vet. Good luck, I hope this helps!
Updated on September 23rd, 2025
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How to slowly switch kitten to adult wet food, even same brand?
What a great question. I have seen many dogs and cats get diarrhea from switching from kitten to adult even if it is the same brand. I would still recommend a 4 or 5 days introduction/ slow switch over. Best of luck and thank you for using Pet Coach.
Updated on September 23rd, 2025

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