Start With a Steady Baseline, Not a New Diet
Begin the diary while your cat is eating her usual food, not on the day you switch to something new. For at least the first stretch, change nothing deliberately. Record the date and time of every meal, the exact flavour and protein source, roughly how much went into the bowl and how much was actually eaten. A cat who leaves half of a rich evening meal tells a different story from one who finishes a small morning portion and is sick soon after, and only a timed log separates those two patterns.
Include everything that is not the main meal. Treats, lickable snacks, milk offered by a visitor, food stolen from another pet's bowl and scraps caught under the table all belong in the diary. Stomach upsets are often blamed on the main food while the real trigger is a repeated extra that nobody thought counted as feeding.
Record What Comes Out as Carefully as What Goes In
Beside each day's food, note stool consistency in plain words — firm, soft, loose or watery — and how many litter tray visits happened. Write down any vomiting, what it looked like in general terms, and crucially how long after eating it occurred. Add appetite, water drinking and energy: a cat who is bright and hungry between loose stools is presenting differently from one who goes quiet, hides and skips meals.
Photographing the litter tray is not pleasant, but dated photos can help a vet judge whether things are improving or worsening across the diary period rather than relying on your memory of a stressful week. Keep the photos with the dated entries so the sequence stays clear.
Change One Thing at a Time and Give It Time
Once the baseline shows a pattern — for example, loose stools mainly after one particular protein, or sickness only on days a certain treat appears — change just that one element. Hold everything else steady and keep logging for several more days. If you swap the main food, drop the treats and add a supplement in the same week, the diary loses its value because any improvement could belong to any of the three.
Note gradual transitions too. Write the proportions as you mix a new food in, and mark the first day the bowl was entirely the new food. Many cats react to the speed of a change rather than the food itself, and the diary is how you prove that to yourself before restricting a diet unnecessarily.
When the Diary Points to the Vet Instead
Take the diary to a veterinarian promptly if there is blood in stool or vomit, repeated vomiting in a short period, complete refusal of food for a day, obvious weight loss, straining in the tray, or a kitten, elderly cat or cat with an existing condition going downhill. Do not use the diary to self-diagnose a food allergy: loose stools can also reflect stress, parasites, a sudden diet change or illness that has nothing to do with ingredients, and only an examination can sort those apart.
Bring the log itself, not a summary from memory. Vets can scan two weeks of timed meals against timed symptoms far faster than they can reconstruct it from guesswork in the consult room, and they may suggest a structured elimination approach based on what your entries already rule in or out.
Keeping the Diary Where It Belongs
Update the diary at feeding time, not at bedtime, while amounts and reactions are still fresh. At the end of each week, add one line noting any non-food changes — visitors, building work, a new cleaning product near the bowls, a missed flea or worm routine — because a so-called food reaction that lines up with a house full of guests may not be about food at all. Reviewing those weekly notes is often the moment the real pattern clicks.
Stored in your KinsLe Pet Passport, the finished diary travels with your cat's vaccination and visit records as one packet, so the next vet who sees her reads the evidence rather than a guess.