A vet who asks you to monitor drinking needs a dependable estimate, and dependable estimates come from a fixed method rather than from watching a bowl and guessing. Measure from one bowl, in one place, with one marked jug. Record exactly six fields each day: the date, the starting level in the measured bowl, the ending level together with any refill, any other water source your cat used, the litter clumps you counted at clean-out, and the food you served that day. Fill the bowl to the same starting level each morning, read the level at the same hour each evening, and write both readings in the level marks of the jug you actually use, so every day speaks the same units as its neighbours.
Set the Method Up Before the First Reading
Choose a heavy bowl your cat already drinks from willingly, set the bowl in a quiet spot, and make the bowl the household's measured source for the monitoring period. Other household water, a dripping tap your cat visits, a mug on a windowsill, another pet's bowl, belongs in the other-source field for that day, written honestly rather than treated as cheating, because the vet reads the total picture. Note a spill or a knocked bowl inside the ending level field when the spill happens, so a low reading never masquerades as a thirsty day. A worked entry follows the six fields in order: date; starting level in the measured bowl; ending level and any refill; other water source used; litter clumps counted at clean-out; food served that day. In a multi-cat home, state that at the head of the note, since a shared bowl measures the household and the vet will interpret the figures differently from a single-cat record.
Read the Note as a Trend With Its Context
Single days mislead. Hot weather raises drinking, a day on wet food lowers visible drinking because the food carries much of the water, and a day of guests can keep a shy cat away from the bowl until night. The food field exists for exactly that reading, as a switch between wet and dry food during the monitoring period changes intake from the bowl without any change in the cat. The litter field cross-checks the bowl, because clumps that grow larger or more frequent alongside rising bowl levels tell a consistent story, while rising levels with unchanged clumps point to spillage, evaporation, or another drinker. Read across a week at a time, compare like days with like, and circle any run of three days that moves steadily in one direction, as runs carry the signal a vet hunts for.
Take the Full Note Back to the Vet
Bring the whole run to the follow-up, not a verbal average, and tell the vet the method as well as the figures, the bowl, the jug marks, the other sources, and the number of cats in the home. Phone before the follow-up date if drinking stops altogether, if your cat strains in the tray, cries, or produces no urine, if vomiting joins rising thirst, or if appetite and energy fall away at the same time, because those combinations deserve prompt advice rather than a completed chart. Ask whether the vet wants the monitoring to continue, change method, or stop, and record that instruction with the final entry. Filed in date order with the method written at its head, the note answers the vet's original question in the vet's own terms, and Pet Passport inside KinsLe stores the daily pages beside the visit record.