Weighing a Senior Cat Monthly on a 5 g Scale

Weigh a cat over 11 once a month on a scale that reads to 5 g, and treat the 3-month trend as the result, not today's figure. Two months of decline in a row, even 100 g each, is a vet visit; 5 percent of body weight lost inside 6 months is a workup. Keep weight and muscle score in separate columns, because a cat can sit at 4.2 kg while trading muscle for fat, and the scale will never tell you which one moved.

Once a month, same scale, same hour

Monthly is the shortest interval that still produces a usable line: 12 points a year instead of 1, which is enough to separate a trend from a bad afternoon. Weigh before the first meal and after the litter box, at the same hour, on the same surface. A hard floor is mandatory; carpet absorbs 20 to 60 g of reading depending on pile depth and where the cat stands. Write the number down the same day, because a figure kept in memory becomes a story within 3 weeks.

Why 5 g resolution, not 50 g

A bathroom scale reads to 0.1 kg, which is 100 g. On a 4.5 kg cat that step is 2.2 percent of body weight, so a real 2-month loss of 180 g disappears into the rounding. A baby or pet scale with 5 g resolution turns the same loss into 36 readable steps, and one costs 30 to 60 USD. The other error is technique: weighing the cat in your arms and subtracting your own weight adds 50 to 100 g of movement noise, which is the same size as the signal you are looking for. Set the cat down alone, wait 3 seconds for the display to settle, and take 2 readings 1 minute apart; if they differ by more than 10 g, take a third.

The 2-month rule and 3 thresholds

Use 3 lines, and act on the first one crossed. A drop of 2 percent in a month is worth a reweigh in 2 weeks. A drop of 5 percent in 6 months, or any 2 consecutive monthly readings lower than the one before, means book an appointment within 7 days. A drop of 10 percent at any speed is same-week, and in a cat that is also eating less it is same-day. On a 4.5 kg cat the 2 percent line sits at 90 g, which is why a 5 g scale is not a luxury: it is the only way to see the line before you are past it.

Weight is not muscle

Fat and muscle move in opposite directions in old cats, and the total can stay flat while both change. Score body condition on the 1 to 9 scale and muscle on the 0 to 3 scale at every weighing, and write both next to the grams. A cat at 4.2 kg with a muscle score of 3 is fine; the same 4.2 kg with a score of 1 is losing lean mass and gaining fat, which is the pattern behind sarcopenia and, often, early chronic kidney disease (CKD). The 2 scores belong in the same row of the log, never in 2 notebooks; the 1 to 9 and 0 to 3 scales are set out in body and muscle scoring.

Month	Weight	Change	Muscle 0 to 3	Action
May	4,520 g	baseline	3	Monthly weighing starts
June	4,470 g	minus 50 g, 1.1 percent	3	Note it, no action
July	4,395 g	minus 75 g, 1.7 percent	2	Reweigh in 14 days
August	4,300 g	minus 95 g, 2.2 percent	2	Book within 7 days
September	4,240 g	minus 60 g, total 6.2 percent	2	Bloodwork, urine, blood pressure

3 hand checks for muscle

Hands find what the scale hides, and 3 checks take 30 seconds. Run a flat palm along the spine: knobs you can count through the coat mean a score of 1 or lower. Feel the shoulder blades: if the edges stand up like 2 fins rather than sitting inside a soft layer, muscle is going. Cup the hips: a hollow the width of 2 fingers on each side of the tail base is a score of 1. Do all 3 in the same order each month, and note the score before you look at the grams, so the number does not anchor your hands.

Weight down, appetite normal: 4 tests to ask for

This pattern has a short list of likely causes, and 4 tests cover most of it. Total T4 catches hyperthyroidism, which raises metabolism and can hide kidney disease behind a normal creatinine. Creatinine with SDMA and urine specific gravity catches CKD, where USG under 1.035 and SDMA above 14 µg/dL show up first. Fructosamine or a glucose curve catches diabetes, usually with values above 250 mg/dL. A GI panel with cobalamin catches chronic enteropathy and lymphoma, which is common past 12 and often presents as weight loss with a good appetite. Add abdominal ultrasound if those 4 come back clean and the decline continues over 2 more months; the same pattern is walked through in weight loss with a normal appetite.

Feeding changes while you wait

Resting energy needs are roughly 70 times body weight in kg to the power 0.75, so a 4 kg cat needs about 198 kcal a day at rest and 220 to 240 kcal at maintenance. Targets for a cat that has to gain are in weight targets. Weigh food in grams rather than scooping, since a scoop varies by 15 to 25 percent between brands, and split the day into 3 or 4 meals of 25 to 35 g wet food. Warm food to 37 °C to raise aroma, and add 10 to 15 ml of water per meal if intake is falling. Recheck weight in 14 days, not 30: the point of the change is to see whether the line flattens.

Five steps to start this week

1. Buy a 5 g baby scale, put it on a hard floor, and zero it with a 500 g weight to check it.
2. Weigh at the same hour monthly and write the grams, body score, and muscle score in one row.
3. Set a 2 percent and a 5 percent line on the log, and act on whichever is crossed first.
4. If 2 months in a row go down, book within 7 days and ask for T4, creatinine with SDMA, USG, and a GI panel.
5. Feed by grams, in 3 or 4 meals, and reweigh in 14 days after any food change.

Terms mentioned in this article

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