Being able to detect if your dog is sick is not that hard. The same principal that you use to detect illness in a friend or family member applies here too. If you have a strong bond with your pet, you will be able to detect even small differences in your dog's behavior or appearance. Less obvious indications such as less enthusiasm than usual, sleeping for longer, reluctance to go for a walk or loss of appetite in the dog can be easily noticed by a caring and attentive owner. However, more obvious symptoms, such as whining for no reason or limping, are sure signs that something is wrong. It is obvious that something has prompted you to think that your dog is sick or dying, so here are some symptoms which will help you first detect if your dog is sick, and then guide you to gauge if your dog is slightly or seriously ill.

Serious Symptoms
These symptoms in all probability will indicate serious problems, that may require emergency treatment. They include sudden breathing difficulties, blood in the urine, bloated abdomen, choking, collapse, convulsions/seizures, excessive foaming at the mouth, fixed and dilated pupils, fainting, fever, inability to stand, extreme lethargy and weakness, pale pink or blue gums, retching, paralysis, staggering and persistent vomiting or vomiting blood. Needless to say, if your dog has broken a bone, got burnt, electrocuted, almost drowned, or has excessive blood loss, then he needs immediate medical attention.

Less Serious Symptoms
If you see your dog displaying any of these symptoms, you should first call your vet and then panic, for chances are that it is not a serious life-threatening condition. Any of these symptoms in isolation may or may not indicate a serious dog health problem:
  • Loss of appetite
  • Bad breath
  • Arching of the back
  • Biting himself
  • Diarrhea
  • Incontinence
  • Lethargy
  • Coughing
  • Muscle tremors
  • Rashes
  • Pain
  • Lumps
  • Redness
  • Discharge from the eyes
  • Smelling badly
  • Ear or nose discharge
  • Restlessness
  • Difficulty in eating
  • Excessive thirst
  • Scratching himself excessively
  • Worms in the feces
Other Signs
When you are wondering about your dog's health, but aren't sure, you can watch your dog for any of these symptoms and signs that will confirm a problem.

Eyes, Ears and Nose: Check to see if there is an increase or decrease in tear production or if the eyes seem cloudy or red. Also check if there is any unusual discharge from the eyes, and if the size of both pupils is the same. Check to see if your dog is squinting, or eyes seem sunken/excessively protruding. Rubbing or pawing at the eyes may indicate a problem. Is there any swelling or discharge from the ears or are they drooping when they normally stand erect. Are they red or smelly? Is your dog rubbing or pawing his ears, shaking his head, or crying when you touch his ears? Is there any blood or other nasal discharge? Is he sneezing or coughing?

Mouth: Check to see if your dog has any swelling of the lips or tongue? Are his gums discolored, or is there any bleeding from the mouth? Check to see if there are any bones or sticks stuck on the roof of the mouth or around the teeth. Can your dog open and close the mouth normally, or does he seem to experience pain while doing so? Is your dog foaming at the mouth or drooling excessively?

While these are some checks you can do to detect if your dog is really ill, the best course of action is to call your vet and follow the instructions he/she gives you. A good step to take when you think your pet is unwell, is to check if his heartbeats are steady and consistent.