Changing your cat’s food is easiest when you control the pace, keep portions consistent and monitor more than an empty bowl. This UK transition plan gives you practical mixing ratios, a reusable 14-day log, guidance for wet, dry, kitten, senior and prescription diets, and clear signs that mean you should pause and contact your vet.
Overview
A gradual change gives your cat time to adjust to a different smell, texture, ingredient profile and calorie concentration. Some cats manage a switch in a week; others need longer, particularly if they are selective, have previously experienced digestive upset or are moving between wet and dry food.
Before opening the new food, check that it is labelled complete for your cat’s life stage. A complementary food is not designed to provide the whole daily diet. Our guide to complete and complementary cat food explains what to look for on the label.
Do not deliberately make a cat go hungry to force acceptance of a new food. Food refusal can become a health concern, especially in overweight cats, kittens, older cats and cats with existing illness. If your cat will not eat, is vomiting repeatedly or develops significant diarrhoea, stop the planned transition and ask a veterinary practice for advice.
The standard transition schedule
| Days | Old food | New food | What to monitor |
|---|---|---|---|
| 1–2 | 75% | 25% | Appetite, stool consistency and vomiting |
| 3–4 | 60% | 40% | Whether your cat accepts the smell and texture |
| 5–6 | 40% | 60% | Stool, water intake and litter-box habits |
| 7–8 | 25% | 75% | Energy, appetite and body comfort |
| 9–10 | 0% | 100% | Continue monitoring for delayed digestive changes |
These percentages refer to the day’s food allocation, not necessarily equal grams. Wet and dry food contain different amounts of water and energy, so weigh or measure each food using its feeding guidance rather than replacing one gram for one gram.
How to estimate the daily amount
Start with the new food’s feeding table and your cat’s current body weight. Treat the recommended amount as a starting point, not a guaranteed prescription. Manufacturers may express guidance by weight, age, activity or a combination of these, and foods vary in energy density.
- Record your cat’s weight. Weigh your cat on the same scales and, where possible, at a similar time of day. If your cat will not stand alone, weigh yourself, then weigh yourself holding your cat and subtract the first reading.
- Find the new food’s daily recommendation. For example, write down the complete daily amount shown for your cat’s weight range. If the label gives a range, begin near the lower or middle part and adjust with your vet’s or retailer’s nutrition guidance if needed.
- Split that amount across meals. Divide the total into the number of meals your cat normally eats. If your cat receives four meals, divide the daily allocation into four portions rather than adding extra food at each serving.
- Apply the transition percentage. On a 25% new-food day, allocate one quarter of the planned daily food to the new product and three quarters to the old product. Measure both separately before combining.
- Reassess body condition. A change in weight, visible ribs, waist shape, appetite or activity may mean the amount needs reviewing. Do not make rapid restriction changes without veterinary advice.
Simple calculation: new food per day = the new food’s full daily amount × the new-food percentage. Old food per day = the old food’s full daily amount × the old-food percentage. Use each product’s own feeding guidance because their daily gram amounts may not match.
For a more detailed comparison of portions and value, see our guide to cat food cost per day in the UK. Cost calculations are most useful when they use the actual daily amount, not just the packet price.
Inputs and assumptions
Before choosing a schedule, write down the details that can change the decision:
- Life stage: kittens need food labelled for growth, while adult and senior foods have different intended uses. For a kitten-to-adult change, use the new food’s life-stage guidance and ask your vet when timing is uncertain. See our UK kitten feeding guide.
- Current body condition: body weight alone does not show whether a cat is carrying too much or too little weight. Note whether your cat is underweight, at an ideal condition or overweight.
- Food format: switching dry to wet, wet to dry or between textures may require a slower schedule. Offer wet food at room temperature and serve small portions if your cat is unfamiliar with it.
- Reason for changing: a preference change can usually be paced. A prescription diet, suspected allergy or urinary-care diet is different and should follow veterinary instructions.
- Treats and extras: count treats, toppers, milk and table scraps as part of the overall intake. During a sensitive transition, keeping extras unchanged—or temporarily stopping them with professional advice—makes reactions easier to interpret.
- Household routine: feed cats separately if one steals food. Use a clean bowl, keep fresh water available and store food as directed on the packaging.
For an intolerance or allergy investigation, avoid changing several ingredients at once. A limited-ingredient or veterinary elimination diet only works if the agreed food is fed consistently, including treats and flavoured extras. Read our guide to cat food for sensitive stomachs and allergies, but use your vet’s plan for diagnosis.
Worked examples
Example 1: adult dry food to another dry food
Suppose the new packet recommends 60 g per day for your cat’s weight and the old packet recommends 55 g. On days 1–2, calculate 25% of each product’s daily amount: 15 g of the new food and 41.25 g of the old food. Split those totals across the usual meals. On days 3–4, use 24 g of the new food and 33 g of the old food. Continue the same calculation until the new food reaches 100% of its own recommended daily amount.
The figures above demonstrate the method, not a universal feeding prescription. Use the amounts printed on your own products and adjust only after considering weight, body condition, activity and veterinary advice.
Example 2: dry food to wet food
Do not calculate the change by matching grams. Record the daily amount or energy guidance for each food, then replace the appropriate share of the day’s allocation. If the new wet food is offered at 25%, keep the remaining dry food at 75% of its planned allocation. Serve the wet portion in a separate dish at first if mixing textures causes refusal. Once accepted, you can combine them or continue separate meals.
Wet and dry feeding each have practical advantages. If you are deciding between them, read our wet versus dry cat food guide.
Example 3: a prescription diet
Use the schedule supplied by your veterinary practice, even if it differs from the standard ten-day plan. Do not dilute a prescribed diet with unapproved treats, food or supplements. If your cat refuses it, contact the practice promptly rather than repeatedly changing products yourself.
Printable 14-day monitoring log
Copy this checklist into a note or print it for each food change:
| Day | Old/new ratio | Amount eaten | Stool | Vomiting | Notes |
|---|---|---|---|---|---|
| 1 | 75/25 | ||||
| 2 | 75/25 | ||||
| 3 | 60/40 | ||||
| 4 | 60/40 | ||||
| 5 | 40/60 | ||||
| 6 | 40/60 | ||||
| 7–8 | 25/75 | ||||
| 9–10 | 0/100 | ||||
| 11–14 | 100% new |
Pause at the previous tolerated ratio if stools become mildly loose or your cat shows reluctance, then speak to your vet if the problem persists. Seek prompt veterinary advice for repeated vomiting, severe or ongoing diarrhoea, blood in the stool, marked lethargy, pain, dehydration, breathing difficulty, or refusal to eat. Urinary straining or repeated trips to the litter tray—particularly in a male cat—should be treated as urgent.
When to recalculate and repeat the plan
Revisit the calculation whenever the input changes. That includes a noticeable weight change, a move between kitten, adult or senior life-stage food, a change in activity, neutering, a new medical diagnosis, a reformulated product or a different wet-to-dry combination. Recheck the packet rather than relying on an old gram amount: feeding tables and calorie concentrations can differ between products.
It is also worth repeating the monitoring process when you buy a different recipe from the same brand, because ingredients, texture and energy density may not be identical. Keep the packet, batch information and a photo of the ingredient list until your cat is settled.
Action checklist: weigh your cat, photograph both labels, calculate each product’s daily amount, choose a pace, measure portions, log appetite and litter-box changes, and review the result after 14 days. If the reason for changing is illness, allergy, urinary trouble or unexplained weight loss, make your veterinary practice part of the plan from the start.
For further feeding guidance, explore our articles on food for indoor cats, urinary-care food and choosing the best cat food in the UK.
