Cats may lose their appetite or become lethargic due to digestive problems, colds, or infectious diseases.
First, if a cat suffers from digestive system diseases such as gastritis, enteritis, or pancreatitis, it may experience symptoms such as decreased appetite and poor mental state. In this case, it is necessary to feed the cat an appropriate amount of probiotics to regulate its condition, and at the same time, take it to the vet for examination and treatment. 
Secondly, if the cat's illness is caused by catching a cold, the owner can administer pet-specific cold medication.
Finally, cats infected with infectious diseases such as feline panleukopenia may also exhibit the above symptoms in the early stages. It is recommended to consult a veterinarian immediately for medication and treatment.
