Loss of Appetite

• Loss of appetite could signal an upset stomach or something as severe as an intestinal blockage. Dogs that do not feel well will not eat.
  
  

Vomiting

• Vomiting is a symptom of many serious diseases, but an upset stomach could also be the cause. The dog's activity before the vomiting episode is an important indicator to the cause.
  
  

Diarrhea

• Diarrhea is a fairly common occurrence in dogs, but if blood is present or the diarrhea persists longer than a day or two, veterinary attention is warranted.
  
  

Frequent Drinking

• Increased water consumption could indicate diabetes or kidney problems and require veterinary attention.
  
  

Shaking Head

• If your dog is constantly shaking its head, it probably has an ear problem. This can be caused by a bacterial or yeast infection, or ear mites.
  
  

Straining to Urinate

• Straining to urinate, crying out while urinating, frequent urination and blood in the urine are signals your dog might have a urinary tract infection or blockage.