2026 ICD-10-CM Diagnosis Code J45.901Unspecified asthma with (acute) exacerbation

ICD-10-CM Codes›J00–J99›J40-J4A›J45

ICD-10-CM J45.901
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

J45.901 is a billable ICD-10-CM diagnosis code for unspecified asthma with (acute) exacerbation. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 202 through 203. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 29 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Asthma.

J45.901 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 229 for payment year 2026.

This medical diagnosis code is frequently used in Pediatrics medical specialties to designate conditions such asthma.

Code Identity

ICD-10-CM Code
J45.901
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified asthma with (acute) exacerbation
Short Description
Unspecified asthma with (acute) exacerbation
Same as the full description in the CMS dataset.
Parent Code
J45.90
Unspecified asthma

Code Classification

ChapterJ00–J99Diseases of the respiratory system
SectionJ40-J4AChronic lower respiratory diseases
CategoryJ45Asthma
This CodeJ45.901Unspecified asthma with (acute) exacerbation

Medicare Risk Adjustment (HCC)Billing

J45.901 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Part D (RxHCC)
RxHCC 229 — Chronic Obstructive Pulmonary Disease, Bronchiectasis, and Other Asthma
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute asthma
  • Acute exacerbation of allergic asthma
  • Acute exacerbation of asthma co-occurrent with allergic rhinitis
  • Acute exacerbation of intrinsic asthma
  • Acute severe exacerbation of allergic asthma
  • Acute severe exacerbation of asthma
  • Acute severe exacerbation of immunoglobin E-mediated allergic asthma
  • Acute severe exacerbation of intrinsic asthma
  • Acute severe refractory exacerbation of asthma
  • Brittle asthma
  • Exacerbation of allergic asthma
  • Exacerbation of allergic asthma due to infection
  • Intrinsic asthma
  • Life threatening acute exacerbation of asthma
  • Moderate acute exacerbation of asthma
  • Thunderstorm asthma

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR RSP009
Asthma
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Airway Remodeling

    the structural changes in the number, mass, size and/or composition of the airway tissues.

  • Asthma

    a form of bronchial disorder with three distinct components: airway hyper-responsiveness (respiratory hypersensitivity), airway inflammation, and intermittent airway obstruction. it is characterized by spasmodic contraction of airway smooth muscle, wheezing, and dyspnea (dyspnea, paroxysmal).

  • Asthma, Aspirin-Induced

    asthmatic adverse reaction (e.g., bronchoconstriction) to conventional nsaids including aspirin use.

  • Asthma, Exercise-Induced

    asthma attacks following a period of exercise. usually the induced attack is short-lived and regresses spontaneously. the magnitude of postexertional airway obstruction is strongly influenced by the environment in which exercise is performed (i.e. inhalation of cold air during physical exertion markedly augments the severity of the airway obstruction; conversely, warm humid air blunts or abolishes it).

  • Asthma, Occupational

    asthma attacks caused, triggered, or exacerbated by occupational exposure.

  • Asthma-Chronic Obstructive Pulmonary Disease Overlap Syndrome

    syndrome with clinical features of both asthma and copd.

  • Conyza

    a plant genus of the family asteraceae. members contain alkenynes, daucosterol, friedelinol, conyzasaponins and other triterpenes.

  • Cough-Variant Asthma

    asthma which is characterized by chronic cough that is nonproductive without other asthmatic symptoms, e.g., wheezing, and paroxysmal dyspnea. cough-variant asthma is accompanied by airway hypersensitivity and may progress to classical asthma without treatment.

  • Dyspnea, Paroxysmal

    a disorder characterized by sudden attacks of respiratory distress in at rest patients with heart failure and pulmonary edema. it usually occurs at night after several hours of sleep in a reclining position. patients awaken with a feeling of suffocation, coughing, a cold sweat, and tachycardia. when there is significant wheezing, it is called cardiac asthma.

  • Status Asthmaticus

    a sudden intense and continuous aggravation of a state of asthma, marked by dyspnea to the point of exhaustion and collapse and not responding to the usual therapeutic efforts.

  • Tylophora

    a plant genus of the family asclepiadaceae. members contain phenanthro-indolizidine alkaloids.

  • Occupational Exposure

    the exposure to potentially harmful chemical, physical, or biological agents that occurs as a result of one's occupation.

Patient EducationClinical

Asthma

Asthma is a chronic (long-term) lung disease. It affects your airways, the tubes that carry air in and out of your lungs. When you have asthma, your airways can become inflamed and narrowed. This can cause wheezing, coughing, and tightness in your chest. When these symptoms get worse than usual, it is called an asthma attack or flare-up.

The full article covers:

  • What is asthma?
  • What causes asthma?
  • Who is at risk for asthma?
  • What are the symptoms of asthma?
  • How is asthma diagnosed?
  • What are the treatments for asthma?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert J45.901 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
493.92 Asthma NOS w (ac) exac
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About J45.901Overview

What is the ICD-10 code for unspecified asthma with (acute) exacerbation?

The ICD-10-CM code for unspecified asthma with (acute) exacerbation is J45.901 (sometimes written as J45901). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is J45.901 (Unspecified asthma) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified asthma with (acute) exacerbation on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does J45.901 group to?

When unspecified asthma with (acute) exacerbation is the principal diagnosis on an inpatient stay, it groups to MS-DRG 202, 203, with relative weights from 0.6700 to 0.9712 depending on complications. Higher weights mean higher Medicare reimbursement.

Is J45.901 a CC or MCC?

CMS lists J45.901 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 29 closely related codes in its exclusion list.

What is the ICD-9 equivalent of J45.901?

Under the General Equivalence Mappings, unspecified asthma with (acute) exacerbation converts to ICD-9-CM 493.92 (asthma NOS w (ac) exac). The mapping is a direct match.

Does J45.901 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: J45.901 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 229 (Chronic Obstructive Pulmonary Disease, Bronchiectasis, and Other Asthma).