Four things, written down

The home log

Four things, not twelve. The version of monitoring you'll still be doing in three months is the only version worth setting up, and none of this takes more than a minute once it's a habit.

What	How often	What you're recording
Her weight	Weekly, same day	A number from a kitchen scale, carrier tared out
Whether she ate normally	Daily	Yes or no is enough
Roughly how much she drank	Daily, by eye	More, less or about the same
The litter box	Daily, when you scoop	Wet clumps there, stool normal or not

Cat Month Weight at the start

Ate normally	Drank	Litter box
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool
yes / no	more / same / less	clumps / stool

The number to watch: losing more than about five percent of her weight in a month, roughly half a pound on a ten-pound cat, is a phone call rather than a wait. Weigh her on the same day each week, before a meal, in the carrier with the carrier's weight taken off. Take this sheet to every recheck; that's the whole reason for keeping it.