Blood is the most known biological fluid in the body. A dog has 90mL of blood per kg, or 1.8L for a dog of 20kg. A cat has 75mL of blood per kg, or 300mL for a cat of 4kg.
Blood contains mainly red blood cells (role in the supply of oxygen to tissues), white blood cells (role in the body's defenses), platelets (role in coagulation), and various metabolites reflecting Function of certain organs: kidneys, liver ...
The blood test is carried out from a sample taken by the veterinarian. It provides important information on the animal's health: anemia, infection, intoxication, renal or hepatic insufficiency ...
Thus, your veterinarian can advise you to carry out a blood test in a systematic way as soon as your pet becomes senior, during the annual comprehensive health examination.