Normal sleep varies
Age, weather, household activity, and individual temperament influence sleep. Kittens and senior cats may sleep more than young adults. A sleeping cat should still wake and respond normally.
What lethargy looks like
A lethargic cat may stay in one place, avoid food, stop grooming, move slowly, hide, seem weak, or show little interest in people or play. These signs may occur with pain, fever, dehydration, anemia, infection, metabolic disease, toxin exposure, or many other illnesses.
When is it urgent?
Seek urgent care for collapse, breathing difficulty, pale or blue gums, repeated vomiting, inability to urinate, severe weakness, neurologic signs, known toxin exposure, or profound lethargy in a kitten.
What to monitor
Record appetite, water intake, urine and stool, vomiting, breathing, temperature if safely measurable, and any recent medication, trauma, or exposure. A sudden unexplained change in energy is worth discussing with your veterinarian even if no single dramatic symptom is present.