Unexplained weight loss in cats


TCS Member
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Young Cat
Oct 25, 2019
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I recently posted about my cat that has been losing weight, but is acting normal. He's eating, drinking and even meowing to go outside. He's been tested for FIV, FeIV and hypothyroidism and it's all clear. However, the vet said he had a high fever and gave him antibiotics and anti-inflammatory medication just in case he has an infection. There are zero signs that there is something wrong with him apart from this weight loss. His side's appear more caved in and I'm lost at what else to look for. Even worse, I noticed that my second cat also is showing the exact same weight loss in the sides (you can also feel their spines more, so they definitely have lost some weight). They're not light or severely underweight where it would cause problems, but it's concerning. I just have no idea what this could be since BOTH have it. Any help would be greatly appreciated. They are both outdoor cats.


Cat Fan especially Black Cats
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Jan 9, 2018
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Colorado USA
Hi! They're going outside and out of your sight, which means they could easily be coming into contact with something, or even ingesting something, that is causing issues.

My suggestion would be to keep them inside for a while, and give them extra food, such as additional kitten food that has more calories.
Also this might have tips for you;
How To Get A Cat To Gain Weight – TheCatSite Articles

If you have a bathroom scale you can weigh them every week or so to see if they start gaining.