SAMHSA Aligned · Reviewed 2026-05-12 · MHPAEA Parity Verified

Medicare Inpatient Rehab Coverage: Hospital Detox and Limited Residential Under Parts A and Advantage

Coverage details, prior authorization, copays, network rules, appeal rights, and ASAM Level coverage for Medicare plans seeking Inpatient Residential Rehab.

(833) 546-3513 Free helpline · 24/7 confidential
Quick Verdict · ~30 sec read
Reviewed by RehabHive Editorial Team · Last updated 2026-05-12
Medicare coverage of inpatient rehab is sharply split: Part A covers inpatient hospital admissions for medically necessary detoxification and acute psychiatric care up to 190 lifetime psychiatric days, but Original Medicare does NOT cover standalone residential SUD treatment (freestanding residential facilities). Select Medicare Advantage plans offer supplemental residential coverage as a plan-level benefit. ASAM Level 3.7 medically monitored withdrawal at a hospital is covered under Part A; ASAM Level 3.5 freestanding residential is generally not covered by Original Medicare. Members seeking residential should evaluate Medicare Advantage plans with supplemental SUD benefits at open enrollment.
SAMHSA & NIDA sourced ASAM Criteria 4ed View 6 sources

ASAM Levels Covered

Medicare aligns its coverage with the American Society of Addiction Medicine (ASAM) Criteria, the national standard for matching patients to the appropriate intensity of care.

ASAM Level Covered Coverage Notes
3.1 Low-Intensity Residential No (Original) / Limited (MA) Original Medicare does not cover; select MA plans add supplemental benefits
3.3 Population-Specific Residential No (Original) / Limited (MA) Same as 3.1 — Original Medicare does not cover
3.5 Medium-Intensity Residential No (Original) / Limited (MA) Original Medicare does not cover; select MA plans cover with prior auth
3.7 Medically Monitored Withdrawal Yes (Hospital) Medicare Part A covers when admitted to acute hospital for detox; 60 days full benefit
4.0 Medically Managed Inpatient (Hospital) Yes Medicare Part A inpatient hospital benefit; up to 190 lifetime psychiatric inpatient days

Prior Authorization

Original Medicare Part A does not require prior authorization for hospital inpatient detox — the hospital admits, treats, and bills Medicare based on medical necessity. Medicare Advantage plans typically require prior authorization for all inpatient admissions including hospital detox; MA plans must approve within 72 hours non-urgent / 24 hours urgent. For freestanding residential under MA supplemental benefits, prior auth requires ASAM Level of Care assessment, ICD-10 SUD and co-occurring diagnoses, prior treatment history, and treatment plan. MA initial authorization typically 7-14 days for Level 3.5 (if covered), with concurrent review every 5-7 days. Standalone residential not covered under Original Medicare — no prior auth process exists.

Cost-Sharing

Medicare Part A inpatient hospital detox cost-share (2026): public function index(),676 deductible per benefit period for days 1-60, 9/day for days 61-90, 8/day for lifetime reserve days 91-150 (60 lifetime), full charges thereafter. Medigap Plan G covers all Part A coinsurance and deductible. Medicare psychiatric hospital benefit limited to 190 lifetime days (general hospital admissions for SUD do NOT count against this 190-day limit). Medicare Advantage plans typically 0-0 admission copay or fixed per-day cost. MA plans with residential supplemental benefit charge public function index()- per admission for residential SUD. Original Medicare without Medigap: 60-day hospital stay for detox could cost public function index(),676 deductible plus extended-day coinsurance.

In-Network vs Out-of-Network

Original Medicare allows any Medicare-accepting hospital. Medicare Advantage plans use networks — HMO MA requires in-network except emergencies; PPO MA allows out-of-network at reduced coverage. For freestanding residential under MA supplemental benefit, only contracted facilities accept the supplemental coverage — verify specific facility with your MA plan before admission. Original Medicare beneficiaries needing standalone residential typically pay cash, use state-funded programs, or transition to Medicare Advantage at open enrollment for supplemental residential coverage.

Step-Therapy & Fail-First

Original Medicare does not apply step-therapy to inpatient hospital admissions. Medicare Advantage plans applying supplemental residential benefit may require documentation of prior outpatient or IOP attempts before approving residential; this functions similarly to commercial step-therapy. Hospital detox under Original Medicare follows medical necessity criteria — patient must require 24-hour medical monitoring (acute alcohol withdrawal with seizure risk, severe polysubstance withdrawal, withdrawal complicated by co-occurring acute medical condition).

Federal Parity (MHPAEA) Protections

MHPAEA does not directly apply to Original Medicare (federal Title XVIII program). Medicare Advantage plans are subject to separate CMS parity rules requiring SUD benefits be comparable in stringency to medical-surgical benefits. The 190-day lifetime psychiatric inpatient limit under Original Medicare is a longstanding exception to parity (psychiatric hospital admissions only — general hospital admissions for SUD detox do not count). CMS 2024 MA Final Rule strengthened parity enforcement on MA plans including residential SUD authorization standards. File MA parity complaints with CMS at 1-800-MEDICARE.

Real-World Example

A 72-year-old Original Medicare beneficiary with Medigap Plan G in Texas required hospital admission for severe alcohol withdrawal with seizure risk. Admitted Friday afternoon to acute hospital; ICU monitoring for 48 hours during peak withdrawal; transitioned to general medical bed days 3-5; discharged with MAT (acamprosate) and outpatient referral on day 5. Total Part A inpatient cost: public function index(),676 deductible (Medigap Plan G paid this). Member out-of-pocket: public function index(). After discharge, member enrolled in Medicare-covered IOP at outpatient hospital department — 20% Part B coinsurance covered by Medigap. Member declined freestanding residential (not covered by Original Medicare); stayed stable with outpatient + acamprosate + MAT clinic follow-up.

Composite example for educational purposes; not a guarantee of coverage. Verify your specific plan benefits.

Frequently Asked Questions

Does Medicare cover inpatient rehab?
Original Medicare Part A covers inpatient hospital admissions for medically necessary detoxification — patient must require 24-hour medical monitoring (severe alcohol withdrawal with seizure risk, complex polysubstance withdrawal). Original Medicare does NOT cover standalone residential rehab at freestanding facilities. Select Medicare Advantage plans add supplemental residential coverage as a plan-level benefit; compare MA plans at medicare.gov.
Is there a 28-day rehab benefit under Medicare?
Not as a standalone benefit. Original Medicare does not cover freestanding 28-day residential programs. Hospital-based inpatient SUD treatment is covered under Part A based on medical necessity, typically 5-14 days for acute withdrawal. Medicare Advantage plans with supplemental residential benefit may cover 28-day freestanding residential — verify specific MA plan benefits at open enrollment.
Does Medicare cover detox?
Yes when medically necessary at a hospital. Medicare Part A covers acute hospital admissions for ASAM Level 3.7 (medically monitored withdrawal) and Level 4.0 (medically managed inpatient withdrawal). Typical hospital detox stay 3-7 days. Medicare Part B covers outpatient detox monitoring. Standalone detox at freestanding residential facilities is generally NOT covered by Original Medicare.
What is the 190-day lifetime psychiatric limit?
Medicare Part A imposes a 190-day lifetime limit on inpatient psychiatric hospital admissions (admissions to specialty psychiatric hospitals). This limit does NOT apply to admissions to general hospitals — even when the primary diagnosis is psychiatric or SUD. Most SUD detox admissions occur at general hospitals and do not count against the 190-day limit. The 190-day limit is a longstanding pre-MHPAEA exception.
How can I get residential rehab coverage with Medicare?
Options: (1) Enroll in Medicare Advantage plan with supplemental residential benefit at open enrollment (October 15 – December 7 annually); (2) Pay out-of-pocket at a state-funded program (often free or sliding-scale for indigent beneficiaries); (3) Transition to Medicaid if income-eligible (dual eligibles have residential coverage via Medicaid); (4) Apply for charitable care at private nonprofit residential facilities.
Does Medicare Advantage cover residential SUD?
Some Medicare Advantage plans cover residential SUD as a supplemental benefit, but coverage is not universal. Specific MA plans with residential SUD benefits typically advertise this as a value-added feature; compare plans at medicare.gov by filtering for "substance abuse residential" or "addiction inpatient" benefit. Coverage levels vary widely.
Does Medicare cover IOP and PHP for SUD?
Yes. Medicare Part B covers Intensive Outpatient Programs (IOP, since 2024 expansion under SUPPORT Act 2.0) and Partial Hospitalization Programs (PHP) for SUD. Member pays 20% Part B coinsurance unless Medigap covers all coinsurance. Medicare Advantage plans typically charge lower copays. PHP requires patient be hospitalized previously or acutely at risk; IOP has fewer prerequisites.
Does Medigap cover residential rehab?
Medigap covers what Original Medicare covers — coinsurance, deductibles, and excess charges. Since Original Medicare does not cover standalone residential rehab, Medigap does not extend coverage to non-covered services. Medigap Plan G fully covers Part A hospital deductible and coinsurance, so hospital-based detox under Part A becomes public function index() out-of-pocket for Plan G holders. For freestanding residential, Medigap does not help; consider Medicare Advantage with residential supplemental.
Are appeals available for Medicare inpatient denials?
Yes. Medicare appeals process for inpatient denials: (1) Redetermination by Medicare contractor within 120 days of initial denial; (2) Reconsideration by Qualified Independent Contractor within 180 days; (3) Administrative Law Judge hearing within 60 days; (4) Medicare Appeals Council; (5) Federal District Court. For Medicare Advantage denials, appeal through MA plan’s grievance process first. For urgent inpatient cases (active hospital admission), expedited appeals available within 72 hours.
How do I find a Medicare-accepting hospital for detox?
Virtually all U.S. acute hospitals accept Medicare. For inpatient detox specifically, call SAMHSA Treatment Locator (1-800-662-4357) or find local hospitals via medicare.gov "Hospital Compare." If you have Medicare Advantage, use your specific MA plan’s provider directory and verify the hospital is in-network. Emergency admissions: any hospital must stabilize regardless of network status under EMTALA federal law.

Sources & Citations

  1. 1
    CMS Medicare Inpatient Mental Health Coverage — CMS guidance
  2. 2
    CMS Medicare Coverage of Opioid Use Disorder Services — CMS guidance
  3. 3
    Medicare.gov Inpatient Hospital Care — CMS resource
  4. 4
    SUPPORT Act 2018 Medicare SUD Provisions — Federal legislation
  5. 5
    SAMHSA Behavioral Health Treatment Services Locator — Federal resource
  6. 6
    NIDA Principles of Effective Treatment — NIH research summary
Free helpline · 24/7

Verify Your Medicare Coverage

Call the SAMHSA National Helpline 24/7 (free, confidential) or use our directory to find Medicare-network facilities offering Inpatient Residential Rehab.

SAMHSA 1-800-662-4357 All Medicare details →
Related Coverage

Compare Medicare with other coverage options

Medicare + MAT (Suboxone, Methadone, Vivitrol)
Coverage details, prior auth, copays
Medicare + Medical Detox
Coverage details, prior auth, copays
Medicare + Partial Hospitalization (PHP)
Coverage details, prior auth, copays
Medicare + Intensive Outpatient (IOP)
Coverage details, prior auth, copays
Medicare + Standard Outpatient
Coverage details, prior auth, copays
Aetna + Inpatient Residential Rehab
Coverage details, prior auth, copays
BCBS + Inpatient Residential Rehab
Coverage details, prior auth, copays
Cigna + Inpatient Residential Rehab
Coverage details, prior auth, copays
UnitedHealthcare + Inpatient Residential Rehab
Coverage details, prior auth, copays

Last reviewed: 2026-05-12 · RehabHive Editorial Team · Based on publicly available Medicare coverage policies, SAMHSA guidelines, and federal MHPAEA regulations.

This information is educational and does not constitute insurance advice. Verify your specific plan benefits directly with Medicare before making treatment decisions.