The dose of a drug and dosage of the drug are two different terminologies. Dose is defined as the quantity or amount of medicine given by the doctor or taken by the patient at a given period. Dosage is the regimen prescribed by the doctor about how many days and how many times per day the drug is to be taken in specified dose by the patient. The dose is expressed in mg for tablets or gm, micro gm sometimes, ml for syrups or drops for kids syrups. The dose is not fixed for a drug for all conditions, and it changes according to the condition or a disease. It also changes on the age of the patient.