Can a hairball cause loss of appetite?

Yes, and it’s a warning sign. A large hairball lodged in the stomach or intestines is the dangerous version of what’s usually a minor nuisance. Cornell flags this directly: a hairball that can’t move through the gut can require surgery and can be fatal without intervention. The combination of repeated retching that produces nothing, dropped appetite, lethargy and abdominal discomfort points at exactly this. It’s not a wait-and-see situation. Long-haired cats and senior cats are most at risk, and the symptoms develop over days rather than weeks.

When to call a vet: appetite loss plus repeated unproductive retching = same-day vet visit, not tomorrow.