Second, look at the mental state. A dog's normal mental state should be lively. If you are mentally weak, you are probably ill.
Third, look at the color of eyes, nose and skin. If the eyes are bloodshot, the nose mirror is dry and the skin is yellow, it is unhealthy. Of course, the diagnosis definitely needs to be tested.
Fourth, look at the feces. Normal feces should be shaped, and diarrhea is definitely a problem.