Dose means quantity (in units of energy/mass) in the fields of nutrition, medicine, and toxicology. Dosage is the rate of application of a dose, although in common and imprecise usage, the words are sometimes used synonyously. Dose means quantity (in units of energy/mass) in the fields of nutrition, medicine, and toxicology. Dosage is the rate of application of a dose, although in common and imprecise usage, the words are sometimes used synonyously.