There are several signs to watch out for if your cat has worms and needs deworming. One of the most common indications is the presence of worms in your cat's feces. These can appear as small, white, rice-like objects or as long, thin strands.
You may also notice changes in your pet’s appetite, weight loss despite a normal or increased appetite, or a pot-bellied appearance. Cats with worms may also experience diarrhea, vomiting, lethargy, or a persistent cough. Or your cat may suddenly be displaying an unkempt coat or have visible worms in the fur or around the buttocks.
In severe cases, cats can become extremely dehydrated, especially if vomiting. Also, some worms feed on the blood, such as hookworms, and it can cause anemia which can eventually lead to death. If you observe any signs of parasites, contact your vet for a diagnosis and appropriate treatment.