Blood test is a laboratory examination of a sample of blood taken from your body, usually from a vein in your arm or rarely from an artery in your wrist, using a needle. A finger prick may also be used.
Blood tests form the fulcrum of diagnosis in modern medicine. They can help assess general state of your health, check the function of organs like liver and kidney, determine whether you have certain diseases and conditions, identify risk factors for heart disease, check whether medicines taken are working, grow the infectious organisms (causing an illness) on blood samples and identify them through a microscope, and obtain DNA sample for genetic testing.
Complete blood count, the most routine blood test, gives information about the cells in your blood. A biochemical analysis measures glucose, cholesterol levels sodium, potassium, chloride, calcium creatinine, etc.