Inaccurate Weight Estimates in Cats

Over 80% of weights obtained by eyeballing were off by 10%

Researchers at the University of Pennsylvania looked at estimates of cats’ weights that were made on admission to the emergency department to see how well they compared to actual weights. All the cats were weighed accurately before treatments were attempted. The goal of the study was to compare the estimated weights based on body condition scores and “eyeballing” to see how closely they matched reality (the accurate weight was obtained from an accurate scale).

The study included 101 dogs and 28 cats that came into the emergency clinic during a two-year period. When the pets were checked for their body condition scores, length of haircoat was noted and weights were estimated using a written form distributed to veterinarians, veterinary students, and veterinary technicians. Then the animals were weighed accurately.

Over 80% of the estimated weights were off by at least 10%. There were not enough cats of differing coat lengths to make any comments regarding haircoat interfering with accurate weight estimates. Cats with higher body condition scores, meaning the chubbier cats, had the biggest difference in actual and estimated weights. Differences tended to err on the side of assigning cats higher weights than the cats actually weighed.

The take-home message from this study is that veterinarians should always get an accurate weight on a cat before any medications are dispensed. You also should know your cat’s actual weight, which can be easily determined by weighing yourself, then weighing yourself holding the cat in your arms and subtracting the difference. Do this monthly. You can catch weight gain or loss early, which is an important health monitor.

An accurate weight is important for dosing medications, including over-the-counter products you might be ordering online such as some flea and tick products. If experienced veterinary professionals are often off on their weight estimates, the odds are high that you will be, too.

Wolf, J.M., et al. “Body condition and hair coat length impact weight estimation in dogs and cats presented to an emergency department,” Journal of the Americican Veterinary Medical Association (JAVMA), March 2023