Refers to the amount of a medicine or drug administered at one time or over a period. Common in medical and pharmaceutical contexts.
The doctor prescribed the appropriate dosage for the patient.
この薬の一日の最大投与量は何ミリグラムですか。
What is the maximum daily dose of this medicine in milligrams?
服用量 refers to the amount taken orally (服用), whereas 投与量 can include any route of administration (e.g., injection, IV).
Compound of 投与 (とうよ, 'administration') + 量 (りょう, 'amount'). The term is a straightforward Sino-Japanese medical term.