Last Updated: 16/12/2025
When to Switch Your Puppy to Adult Dog Food: A Vet's Guide
Confused about the switch to adult dog food? Our vet-written guide cuts through the confusion, explaining how breed size, maturity, and nutrition impact the decision. Learn the right time to transition your pup and the best way to introduce the new food smoothly.
Author: Dr Brittany Ward BVSc
Reading Time: 10 minutes - short read
It's a joyful milestone when your adorable, fluffy puppy starts to look and act like a proper adult dog. But figuring out exactly when to trade in the puppy kibble for an adult formula can feel like a tricky guessing game! Many pet parents rely on age alone, but getting the transition time wrong can deprive your growing dog of vital nutrients, potentially leading to long-term health issues like joint problems or obesity.
The secret? It's not just about the calendar; it's about understanding your dog's unique growth rate and nutritional needs. We'll walk you through the science of puppy maturity, offer tailored age guidelines based on breed size, and give you a simple, step-by-step plan for a smooth switch, helping your best friend thrive as they enter adulthood.
Understanding puppy growth and nutritional needs
While using your puppy's age is a good start for deciding when they are mature, there isn't one perfect age that suits all dogs. A variety of factors impact when your dog reaches their full adult size.
The science of puppy maturity
Maturity is generally reached when a puppy's growth plates close. These are soft, cartilaginous areas in the long bones that drive bone, muscle, and organ growth through rapid cell division.
Because of this intense growth, puppy diets need high amounts of energy and protein. Rapidly dividing cells require large amounts of protein (as building blocks) and energy (from fat) to prevent delayed growth. Some puppies can gain a kilogram or more per week!
Why puppy food must be carefully balanced
A specialised puppy diet is crucial because it is designed to manage this rapid development, preventing both delayed growth and excessive growth:
- Preventing joint Issues: Growth that is too fast or excessive weight gain can lead to developmental joint diseases like Elbow Dysplasia.
- Controlling key nutrients: Nutritionally complete puppy diets have carefully regulated levels of calcium and phosphorus to control healthy bone growth, and protein and fat to prevent excessive weight gain.
- Supporting development: Puppy diets also nourish other vital areas as your dog grows, including the developing brain, coat and immune system, and the arrival of adult teeth.
Estimating the right time to switch
Your puppy needs to transition to an adult diet once their growth stops (when the growth plates close). Since taking constant X-rays to confirm closure isn't practical, we use an estimation based on key individual factors:
- Breed and size: This is the biggest factor, as small breeds mature much faster than giant breeds.
- Gender and health: Size variations exist even within breeds (males versus females), and underlying health issues (like food allergies) can affect nutritional needs and growth timelines.
When to transition based on your dog's breed size
Small and Toy Breed Dogs
Small and Toy Breed Dogs will mature the fastest, reaching their adult size and weight the earliest. Small Breeds are those typically weighing less than 10kg at their adult weight, such as the Cavalier King Charles Spaniel, Dachshund and Shih Tzu.
It is recommended to transition small breed dogs to an adult food at around 9-12 months. Those with adult weights closer to 10kg, are best transitioned at 12 months of age, while toy breeds under 4kg may be able to transition on to adult food at 8-9 months of age.
If you have an intermediate breed, such as the French Bulldog, then it is best to wait until 12-13 months of age.
Medium Breed Dogs
A Medium Breed Dog is any dog weighing between 10-25kg, most commonly including breeds like the Border Collie, Cocker Spaniel and Beagle.
It is recommended to transition most medium breed dogs to an adult diet between 12-14 months of age, with larger medium breeds being left slightly later. Intermediate breeds, or those with an expected adult weight around 23-27kg like the American Staffy may remain on a puppy food until 15-16 months of age.
Large and Giant Breed Dogs
Large Breed dogs can be broken into two categories; large breeds with an adult weight 25-40kg and giant breeds, which is anything with an adult weight over 40kg.
Large breed puppies like the German Shepherds or Labradors are recommended to stay on a puppy food until 15-18 months of age. Giant breeds like the Great Dane or Irish Wolfhound should stay on a puppy food until 18-24 months of age.
Why your vet is your best partner in the transition
The breed-specific transition ages are ranges because individual dogs mature differently and some breeds fall between size categories (like the French Bulldog or American Staffy).
To pinpoint the exact right time for your pup, your veterinarian will be your best partner. They determine the optimal age for transition by evaluating:
- Age and breed: Using the standard guidelines as a starting point.
- Growth rate: Assessing if your puppy is growing too fast or too slow.
- Body Condition Score (BCS): Ensuring your pup is maintaining a healthy weight and not becoming overweight.
Your vet's role is crucial, especially for mixed breeds where the adult weight is uncertain, or for purebreds with growth variations. They may recommend:
- Staying on puppy food longer: If your pup has a joint condition like Hip Dysplasia.
- Transitioning sooner: If they have reached around 80% of their adult size and are quickly gaining excess weight.
- Specific diets: If health conditions require a specialised food.
If you are ever in doubt about the best time to switch your puppy's diet, always consult your veterinarian.
How to transition your dog's food smoothly
Why is it important to transition?
Your puppy's nutritional needs won't change overnight; they aren't a puppy one day and an adult the next. Rather growth and metabolism will slow and change as they transition into adulthood. Their nutrient requirements will slowly adjust as their body settles into adulthood. Likewise, their diet should transition to match this.
A puppy's digestive system will also have adapted to the diet they've been eating, already prepared to digest what it expects is coming. Suddenly introducing a new food could throw off that digestive system balance, leading to digestive upset.
How do I transition to an adult food?
The general transition guide is to increase the amount of new food in the meal by 25% every 2-3 days. For many dogs, this will look like:
- Day 1-2: 25% Adult Food with 75% Puppy Food
- Day 3-4: 50% Adult Food with 50% Puppy Food
- Day 5-6: 75% Adult Food with 25% Puppy Food
- Day 7 Onwards: 100% Adult Food
For more detailed information on the diet transition process, check out our article How to Introduce a New Food to Your Pet.
What do I need to monitor for during the transition?
Not all dogs will handle a diet transition the same way, some may have a sensitive stomach or be fussy about flavours. During the transition, monitor your dog for any vomiting, diarrhoea, food refusal, tummy gurgles, constipation, excessive drooling, or bad breath.
Dogs with a known sensitive stomach will generally need to be transitioned more slowly. If your puppy reacts to their new adult food, then you may need to prolong the transition period to allow them to adapt to it.
If your puppy has any symptoms that persist for longer than 24 hours and cannot be resolved by stopping the new food or a bland diet, then it is recommended to take them in to your regular veterinarian for examination.
How often should I feed my puppy vs adult dog?
How often your puppy gets fed will depend on their age. By the time that your puppy comes to live with you in their furever home at 6-8 weeks of age, they will need to be fed 3-4 times a day. After 16 weeks or 4 months of age, your pup will only need to be fed 3 times a day until they are 6 months of age. Between 6-12 months of age, you can transition your puppy onto twice daily feeding.
Once your dog is on their adult diet, you can opt to feed them once or twice a day depending on your personal preference or your individual dog's needs.
Even though your puppy's number of daily feedings is decreasing, they will still need to eat enough to meet their energy requirements for growth.
Not sure how much food your puppy should be eating? Why not check out our article on How Much and How Often Should I be Feeding my Puppy?
What's the best adult dog food?
It is essential that your dog’s food meets the minimal nutritional standards set by AAFCO (Association of American Feed Control Officials) for protein, fat, vitamins, and minerals. However, we highly recommend choosing a premium adult diet for your dog.
What makes a premium diet better?
Premium diets go above and beyond the AAFCO minimum guidelines to truly nourish your dog, not just feed them.
Benefits for your dog:
- Superior quality: They use high-quality, easily digestible ingredients.
- Targeted support: They include added therapeutic ingredients to support key areas of health:
- Skin and coat health.
- Brain development and immune function.
- Healthy digestion and heart health.
- Joint health (especially in large breed formulas).
- Life-long health: These added ingredients help set your dog up for a long, healthy life.
Benefits for you (the owner):
- Less mess: High digestibility means less waste and reduced faecal output and odour.
- Smooth transition: Premium brands often offer options for all life stages, making it easy to stick with the same trusted brand from puppy through to senior.
- Cost-effective: While initially pricier, premium diets can often be more cost-effective in the long run due to increased digestibility, better health outcomes and less digestive upset.
Breed-specific options
Some premium brands like Royal Canin and Advance offer breed-specific diets. These formulas are specially tailored to the nutritional values required by certain breeds (such as Oodles or French Bulldogs) and often feature a kibble shape designed specifically to suit their jaw size and eating style.
Learn more in our Breed Specific Dog Food Guide and What is the Best Dog Food?
FAQs
Transitioning your puppy to an adult diet at the right time is one of the most important steps you can take to set them up for a long, healthy, and happy life. Using the age and breed-size recommendations here is a fantastic starting point. Remember, if you're ever in doubt, the best thing you can do is check in with your vet. They can help you factor in your dog's individual growth rate and Body Condition Score to ensure your pup gets the perfect fuel for their wonderful new chapter!
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Tue 16 Dec 2025
Edited by Dr Gillian Hill BVSc (Hons)Dr Brittany Ward BVSc
Veterinarian
Dr. Brittany graduated from James Cook University in 2019 with a Bachelor of Veterinary Science and started working in her home town in the Wide Bay-Burnett Region. She has always been excited about working in the veterinary industry, but over the last few years has grown especially fond of dog behaviour and training, surgery and orthopaedic disease.
