There are several signs that may indicate that your pet is sick. Some common signs to look out for include changes in appetite, lethargy, vomiting, diarrhea, coughing, sneezing, changes in behavior, excessive licking or scratching, and difficulty breathing. It's important to monitor your pet closely and consult with a veterinarian if you notice any unusual symptoms or behaviors. Regular veterinary check-ups can also help detect potential health issues early on.