A prescription is a written or electronic order from a licensed clinician for a medication. It specifies the drug, the dose, the route, the frequency, and the quantity to be dispensed. It also includes the prescriber's information and the patient's name. In most countries, prescription drugs can only be dispensed by a pharmacist with a valid prescription. The system is designed to ensure that patients receive medications that require professional oversight.

Prescriptions are not just paperwork. They are a legal document and a clinical decision. The prescriber assesses the patient, considers the diagnosis, reviews other medications and conditions, and chooses a drug and dose. The pharmacist checks the prescription for appropriateness, interactions, and dosing errors. Both are part of the safety net. Electronic prescribing has reduced errors from illegible handwriting, though new types of errors have emerged, such as selecting the wrong drug from a dropdown menu.

What a prescription includes:

• Patient information. Name, date of birth, and sometimes address.
• Drug name and strength. The specific medication and dose.
• Directions. How much, how often, and by what route.
• Quantity. How much to dispense.
• Prescriber information. Name, license number, and contact details.

Refills are specified on the prescription. Controlled substances have additional restrictions, including limits on quantity and refills.