What is the Two-Midnight Rule?
Short answer
The Two-Midnight Rule is Medicare's guideline for when a hospital stay should be billed as inpatient. An inpatient admission is generally appropriate when the admitting physician reasonably expects the patient to need medically necessary hospital care spanning at least two midnights, and documents why. Shorter expected stays are usually treated as outpatient or observation, with a few exceptions.
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How the benchmark works
CMS introduced the rule in the fiscal year 2014 inpatient payment rule, effective October 1, 2013. The decision is judged on what the admitting physician could reasonably expect when writing the admission order, based on the information available at that moment.
Time the patient has already spent receiving hospital care, such as in the emergency department or in observation, counts toward the two midnights. If the patient later leaves sooner than expected (they improve, transfer, leave against medical advice or die), the admission can still be appropriate as long as the original expectation was reasonable and documented.
Exceptions
- Inpatient Only list: procedures CMS only pays for as inpatient, regardless of expected length of stay.
- Newly started mechanical ventilation: unforeseen ventilation (not planned for a procedure) can support inpatient status even when less than two midnights is expected.
- Case-by-case exception: the admitting physician can judge that inpatient care is needed for a shorter stay, based on the patient's history, severity of illness and risk of an adverse event. That reasoning must be clearly documented.
Medicare Advantage
Since January 1, 2024, Medicare Advantage plans must follow traditional Medicare's coverage criteria for inpatient admissions, including the Two-Midnight Rule (CMS-4201-F). Where Medicare's criteria are fully established, plans can't use stricter internal criteria to deny an admission. This gives hospitals a concrete rule to cite in peer-to-peer calls and appeals with these plans.
What the documentation needs to show
- Why the patient needs hospital-level care, not just that they are sick
- The expected length of stay and the reason for it
- Risk factors and severity of illness that support the decision
- A clear, timely, signed inpatient admission order
- For a case-by-case exception, the specific clinical reasoning
Key terms
Common questions
Does observation or emergency department time count toward the two midnights?
Yes, toward the expectation. Time already spent receiving hospital care counts when judging whether the stay will cross two midnights. The inpatient stay itself still begins when the inpatient order is written.
What is the two-midnight presumption?
It's a review policy that goes with the rule. Inpatient stays that cross two midnights after the admission order are generally presumed appropriate and are not a focus of Medicare contractor medical review, unless there's evidence of misuse.
Do Medicare Advantage plans have to follow the Two-Midnight Rule?
Yes. Since January 1, 2024, Medicare Advantage plans must apply traditional Medicare's inpatient admission criteria, including the Two-Midnight Rule.
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