2027 ICD-10-CM Diagnosis Code G47.421Narcolepsy in conditions classified elsewhere with cataplexy
ICD-10-CM Codes›G00–G99›G40-G47›G47
- Billable — Valid for Submission
- Chronic Condition
G47.421 is a billable ICD-10-CM diagnosis code for narcolepsy in conditions classified elsewhere with cataplexy. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 91 through 93. The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as cataplexy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Sleep wake disorders.
G47.421 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 355 for payment year 2027.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for G47.421.
Medicare Risk Adjustment (HCC)Billing
G47.421 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.
Source: CMS Payment Year 2027 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.
- Cataplexy
- Narcolepsy
- Secondary narcolepsy
- Secondary narcolepsy with cataplexy
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G47.421: its own notes plus those printed at G47.42, G47, and Chapter 6. A note printed at a category, block or chapter applies to every code under it.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Code First
The underlying condition named in the note is sequenced before this code.
- underlying condition
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name G47.421, its category, or a range that includes it.
Excludes2 2
These codes carry an Excludes2 note naming G47.421: its condition is not part of those codes, and both may be reported when the patient has both.
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.
Clinical InformationClinical
Sleep Disorder
a change from the patient's baseline sleeping pattern, in the hours slept and/or an alteration/dysfunction in the stages of sleep.
Patient EducationClinical
Sleep Disorders
While you are sleeping your brain and body functions are still active. Sleep is a natural process that helps your body restore energy, supports learning and memory, and keeps you healthy.
The full article covers:
- What is sleep?
- What are sleep disorders?
- What causes sleep disorders?
- What are the symptoms of sleep disorders?
- How are sleep disorders diagnosed?
- What are the treatments for sleep disorders?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert G47.421 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G47.421Overview
What is the ICD-10 code for narcolepsy in conditions classified elsewhere with cataplexy?
The ICD-10-CM code for narcolepsy in conditions classified elsewhere with cataplexy is G47.421 (sometimes written as G47421). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is G47.421 (Narcolepsy in conditions classified elsewhere) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report narcolepsy in conditions classified elsewhere with cataplexy on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G47.421 group to?
On inpatient claims, narcolepsy in conditions classified elsewhere with cataplexy maps to MS-DRG 91, 92, 93, with relative weights from 0.7783 to 1.7050 depending on complications. Higher weights mean higher Medicare reimbursement.
Can G47.421 be a principal diagnosis?
No. This is a manifestation code: narcolepsy in conditions classified elsewhere with cataplexy describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.
What is coded first with G47.421?
The Code First note at G47.42, which applies to G47.421, reads: underlying condition. When one of these applies, it is sequenced before G47.421.
Does G47.421 risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage: G47.421 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 355 (Narcolepsy and Cataplexy).
