How to appeal an insurance denial for a hospital stay

A hospital denial can take one of three forms, and each one has its own appeal route and its own clock.

• Your status. You were kept as an outpatient under observation instead of being admitted.
• Your discharge. You were told you no longer need inpatient care, and you think it is too soon to leave.
• Payment after the fact. The plan denied some or all of the stay after you went home.

Find the paper that announced the decision, whether a notice handed to you in the hospital, a denial letter, a Medicare Summary Notice or an Explanation of Benefits, and write down the date you got it. Some deadlines are measured in hours.

Under Medicare, you become an inpatient only when you are formally admitted with a doctor’s order. Emergency care and observation are outpatient services, and you can be an outpatient even if you spend the night in a regular hospital bed.

The label affects what you pay. It also matters later, because Medicare covers a skilled nursing facility only after an inpatient stay of at least 3 days in a row, and time under observation does not count toward those 3 days, even overnight.

If you get observation services for more than 24 hours, the hospital must give you a Medicare Outpatient Observation Notice, called the MOON, no later than 36 hours after observation starts. CMS says the MOON requirement covers Medicare Advantage enrollees as well.

Medicare suggests that you or a caregiver ask every day of the stay whether you are an inpatient or an outpatient, and write down each answer.

Medicare’s admission rule says an inpatient admission is generally appropriate when the admitting doctor expects you to need hospital care that crosses two midnights. Shorter admissions can also qualify when the doctor’s judgment is supported by the medical record. Either way, the reasons behind the doctor’s expectation must be written in your chart, such as your history, how severe your symptoms are and your risk of a bad outcome.

Medicare Advantage plans must follow Traditional Medicare’s coverage rules, and the regulation names the inpatient admission criteria in 42 CFR 412.3 as an example. Those provisions apply to coverage beginning January 1, 2024. In a February 2024 memo, CMS told plans that they “are required to follow these inpatient admission criteria”, which include the two-midnight benchmark, and that an algorithm alone cannot be the basis to deny an admission or downgrade it to observation.

Once a Medicare Advantage plan approves an inpatient admission, in advance or during the stay, it may not later deny coverage for lack of medical necessity except for good cause or fraud. CMS described its April 2025 rule this way: plans can reopen an approved admission only for obvious error or fraud.

What to ask for: the admission order, the admitting doctor’s notes and the hospital’s case-management notes, which show whether the expected stay and the reasons for it were documented.

Every Medicare inpatient, in Original Medicare or a Medicare Advantage plan, should get the Important Message from Medicare. The hospital must give it to you within 2 days of admission and give you a copy again before you leave.

To challenge a discharge, call the Beneficiary and Family Centered Care Quality Improvement Organization (BFCC-QIO) listed on that notice. The request must be made no later than the day of discharge, by phone or in writing, and Medicare Advantage enrollees have the same deadline.

If you meet it, Medicare says you can stay in the hospital while you wait for the decision and you won’t have to pay for the stay beyond your usual coinsurance and deductible. In a Medicare Advantage plan that never authorized the admission, you may need a separate appeal for the plan to pay.

The hospital carries the burden of proving the discharge is correct. You will get a Detailed Notice of Discharge explaining its reasons, and the QIO decides within one calendar day after it has the records it asked for.

If you miss the deadline in Original Medicare, you can still ask the QIO for review, including within 30 days after you leave, without the same protection from charges. In a Medicare Advantage plan, you can ask the plan for an expedited reconsideration instead.

If your status changed during the stay. With Original Medicare, if you were hospitalized on or after February 14, 2025, and the hospital switched you from inpatient to observation, you can ask the BFCC-QIO for a fast appeal using the Medicare Change of Status Notice (CMS-10868).

You qualify if you had no Part B, or if you stayed 3 or more days but were an inpatient for fewer than 3. Ask before you are released; you can still ask later, but a late request loses the billing protection.

The separate window for appealing older status changes from past stays closed on January 2, 2026, except for late filers who can show good cause.

Employer plans governed by federal ERISA rules must treat a claim as urgent when the normal timeline “could seriously jeopardize the life or health of the claimant or the ability of the claimant to regain maximum function”, or when a doctor says waiting would cause severe pain that cannot be adequately managed. If a doctor who knows your condition says the claim is urgent, the plan must treat it that way. You can ask for an urgent appeal by phone, and the plan must decide it within 72 hours.

If a private plan denied or downgraded an admission, ask for the criteria it used; employer plans must provide them or a free copy on request.

If a plan approved a set number of hospital days or treatments and then cuts them short, that counts as a denial, and the plan must tell you early enough for you to appeal before the care ends. A request to extend urgent care made at least 24 hours before the approval runs out must be answered within 24 hours. Plans covered by the Affordable Care Act’s appeal rules must continue coverage of ongoing treatment while the appeal is pending.

In an urgent situation you can ask for an external review at the same time as your internal appeal, and an expedited external review is decided no later than 72 hours after the request. Full timelines are on the pages for employer plans, Marketplace plans and Medicaid.

Some denials come weeks later, when the plan reviews the hospital’s claim. Read who the letter is addressed to and whether it says you owe anything.

• Medicare Advantage, in-network hospital. Plan contracts must bar network providers from billing you for amounts that are the plan’s obligation. CMS has also said your liability cannot be set until the plan decides the hospital’s claim, which preserves your right to appeal. Reviews done after a stay must follow the same coverage rules as reviews done before or during it.
• Employer or Marketplace plan. A denial for care you already received is a post-service claim. If the letter is addressed to you, you can appeal it yourself. Call the hospital’s billing office, ask whether it is appealing too, and ask it to hold the bill while any appeal is pending.
• Original Medicare. Check your Medicare Summary Notice. Appeals of items on that notice go to the address listed on it.

For any appeal of a past stay, request the itemized bill, the discharge summary, the doctors’ progress notes and copies of any MOON or Important Message you signed. Then check the deadline rules for Medicare Advantage, Original Medicare, employer plans, Marketplace plans and Medicaid.