How Fellbert compares before and after

Fellbert is a health diary. The analysis, the Fellbert Recap, describes what you have entered. It makes no diagnosis, proves no cause and does not replace a veterinary assessment. This page explains exactly what the comparison does, so that you can read its statements correctly.

What an entry is

Every day Fellbert asks you short questions about how your pet is doing. You choose which ones from a list of eleven: appetite, general wellbeing, vomiting, stool, seizures, getting up and jumping, limping, scratching or licking, breathing at rest, drinking, amount of urine. With Premium you can add questions of your own; in total there are at most ten questions per pet, six are recommended. Every answer is an entry. A day without an answer is a day without an entry, not a good day.

What “notable” means

Every question has answers that count as notable: for vomiting “once” and “several times”, for appetite “reduced” and “none”, for stool “soft”, “watery” and “hard”. “Not seen” is not an answer but a missing entry. For stool there is also “definitely none”; that is counted separately and rated neither as notable nor as unremarkable.

What triggers the comparison

Every change to the plan that affects food, medication, daily amount or meals. Adding the strength of a medication afterwards triggers no comparison, because it changes nothing about the treatment.

Which days are compared

The 14 days before the change and the 14 days after it. The day of the change itself counts towards neither side. With a change of food, the “after” only starts once the switch is complete; the transition days are counted separately and not compared. If the topic skin is chosen for the pet, a change of food is compared over 28 days on each side, because hardly anything shows there within two weeks. For medication it stays at 14 days.

When the comparison appears

Only once both periods are complete and at least three quarters of the days in each have an answer: 11 of 14, 21 of 28. Until then Fellbert shows on which day the comparison will appear or, if answers are missing, how many each period needs. If you start the diary on the day of the change, you have no “before” for that change; there will be no comparison.

Fellbert Recap for Finni with sample data: since the change of food, Finni seems to be doing better. Clearly better: stool, before 6 of 11 days, after 0 of 13 days. Slightly better: appetite and vomiting. Little difference: general wellbeing and drinking. — The comparison is ready.

Fellbert Recap for the same dog with a week without entries: entries are missing for a comparison, each period needs at least 11 days with an answer. — The same pet with a week without entries: no comparison yet.

How the verdict comes about

Shares are compared, not days: the share of notable days among the days with an answer, before against after. Below 15 percentage points of difference the verdict is “little difference”. From 15 percentage points it is “slightly better” or “slightly worse”, from 35 “clearly”. In addition, the notable days must differ by at least three; two days are not a finding. Less that is notable means better.

These thresholds are product decisions, not statistics. They are not clinically validated and demonstrate no significance. That is why Fellbert words the sentence above the comparison cautiously (“seems to be doing better”, “hardly anything has changed”) and shows the numbers under every verdict.

What the comparison cannot do

It proves no cause. After a bad spell things often improve by themselves.
If something else was changed in the same period, Fellbert cannot tell the changes apart and says so.
It does not know whether a medication was actually given, only whether it was in the plan and ticked off.
It only sees what was entered. What nobody saw is missing.

Over the whole time and Earlier in the plan

Besides the comparison, the recap shows phases with the same plan (highlighted from 14 days, if at least three quarters of the days were entered), every month with its share of notable days, runs (only days entered without a gap; a day without an answer ends a run, which is why a run is not a flare-up) and the weight with date and number of measurements. “Earlier in the plan” shows, for a chosen food or medication, every period in which it was in the plan, with the observations from that time. “Was in the plan” does not mean “was certainly given”.

What you can do with it

Talk to your vet practice about what you notice. For the chosen period, the PDF report contains the phases with the same counts, plus plan, doses given, observations and weight. You show the individual before and after comparison in the app. Do not change any treatment without consulting your vet.

Last updated: 15 October 2026, applies to Fellbert 1.24.0. If rules change, this page is updated with a date.