Should I Be Concerned About My Cat’s Unplanned Weight Loss?

There’s a reason why so many weight loss cat foods exist. To keep Fluffy healthy, there may come a time when she needs a little help with weight control. But what if you saw her suddenly and inexplicably drop a few pounds? You’d rightfully be concerned.

While controlled weight loss can be right for some cats, unplanned slimming could signal an underlying medical issue. Whether subtle or dramatic, here’s what to know if your cat starts unexpectedly losing weight.

Is your Cat Underweight?

Sometimes it can be hard to detect weight loss in cats until it’s very noticeable. That’s because their coats often obscure signs they’re dropping pounds.

You can, however, look for other physical tells that your cat is losing weight by checking:

  • Their ribs. Run your hand down their back and along their side. The bonier it feels, the more likely you have a kitty that’s lost a significant amount of weight.
  • Their hind legs. If they show through the fur and you can distinctly see their bones as they walk, the weight loss is marked enough to warrant concern.
  • The curve of their stomach. When you look down at your cat from an aerial perspective, see if their stomach makes a significant inward slope behind its ribs. If so, time to take action.
  • Their muscle mass. Muscle definition is a show of good health in kitties of all sizes. Should the shoulders start protruding, it could mean they’ve lost a significant amount of weight.

At your cat’s annual check-up, you’ll also want to note their weight. This will give both you and the vet a baseline to gage from.

If you suspect an issue, weigh your cat at home by first standing on the scale and notating what it registers for you alone. Next, gently wrap your cat in a towel and weigh the both of you together. Subtract your original weight from the second weigh-in to get an idea of how much your cat has lost.

What Causes Weight Loss

Though there are several causes of unexpected weight loss, they’re very rarely positive. Even senior cats, in which you might expect some slimming, are more than likely displaying the beginning stages of something medical.

Infections and diseases both acute and chronic can lead to pronounced weight loss. You may notice a change if Fluffy loses fluids, fat, muscle, or all of the above; though it’s hard to know the true cause without a vet’s diagnosis.

Generally speaking, there are some common reasons cats lose weight including:

  • Liver or kidney disease
  • Bacterial, protozoal and viral infections
  • Diabetes
  • Feline Immunodeficiency Virus
  • Hyperthyroidism
  • Inflammatory bowel disease
  • Cancer
  • Gum disease or dental issues
  • Feline Leukemia Virus
  • Ulcers
  • Heartworms or parasitic worms
  • Pregnancy
  • Depression


Keep in mind that this list is not exhaustive, and only a vet can tell you for sure what may be causing your cat to lose weight.

Responding to Weight Loss

Loss of appetite, vomiting, and diarrhea can all be symptoms of more serious diseases. They also cause weight loss in cats that could be detrimental to their overall health. Impaired intake and nutrient losses should be treated with extreme caution.

Try to get them to the emergency vet as quickly as possible. If you can, take video of the vomiting episode and save a stool sample to help aid in diagnosis.

Most importantly, you should absolutely refrain from changing cat foods, even if Fluffy is refusing to eat. Doing so could result in a delayed diagnosis. Until your vet prescribes a change in food as part of your cat’s recovery process, stick to the high-quality cat food they’re used to eating.

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