The Two-Midnight Rule refers to the criteria used to determine whether inpatient admission is reasonable and necessary for the purpose of payment under Medicare Part A.

The inpatient admission is generally payable under Medicare Part A if the attending physician (or other qualified practitioner) expects the patient to need at least two midnights of medically necessary hospital services, and medical records support that expectation. If the admitting practitioner expects to keep the patient in the hospital for fewer than two midnights, the services would generally be payable only as an outpatient or Part B payment.