2026 ICD-10-CM Diagnosis Code P55.9Hemolytic disease of newborn, unspecified

ICD-10-CM Codes›P00–P96›P50-P61›P55

ICD-10-CM P55.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

P55.9 is a billable ICD-10-CM diagnosis code for hemolytic disease of newborn, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 791, 793. Coders also document this condition as erythroblastosis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Hemolytic jaundice and perinatal jaundice.

For Medicare Advantage risk adjustment, P55.9 maps to CMS-HCC Category 109 (Acquired Hemolytic, Aplastic, and Sideroblastic Anemias) under the V28 model, adding a risk factor of about 1.144 for a community, non-dual, aged beneficiary in payment year 2026.

Code Identity

ICD-10-CM Code
P55.9
Billable Status
Yes — Valid for Submission
Code Describes
Hemolytic disease of newborn, unspecified
Short Description
Hemolytic disease of newborn, unspecified
Same as the full description in the CMS dataset.
Parent Code
P55
Hemolytic disease of newborn

Code Classification

ChapterP00–P96Certain conditions originating in the perinatal period
SectionP50-P61Hemorrhagic and hematological disorders of newborn
CategoryP55Hemolytic disease of newborn
This CodeP55.9Hemolytic disease of newborn, unspecified

Medicare Risk Adjustment (HCC)Billing

P55.9 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.

CMS-HCC V28 Category (Payment Model)
HCC 109— Acquired Hemolytic, Aplastic, and Sideroblastic Anemias
Payment HCC · PY 2026 one of 37 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+1.144
community, non-dual, aged · ranges 0.529–1.815 across segments
Hierarchy
Top of its hierarchy
HCC 109 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Part D (RxHCC)
Not mapped
P55.9 does not risk-adjust in the RxHCC prescription drug model

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.

  • Erythroblastosis
  • Isoimmunization
  • Late anemia of newborn
  • Late anemia of newborn due to isoimmunization
  • Neonatal anemia

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 PNL007
Hemolytic jaundice and perinatal jaundice
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Blood Disorders

Your blood is living tissue made up of liquid and solids. The liquid part, called plasma, is made of water, salts and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells and platelets.

Read the full article at MedlinePlus

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

Convert P55.9 to ICD-9-CMHistory

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

ICD-9-CM
773.2 NB hemolyt dis-isoim NEC
Approximate The match is approximate rather than exact.

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 P55.9Overview

What is the ICD-10 code for hemolytic disease of newborn, unspecified?

The ICD-10-CM code for hemolytic disease of newborn, unspecified is P55.9 (sometimes written as P559). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is P55.9 (Hemolytic disease of newborn) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hemolytic disease of newborn, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does P55.9 group to?

When hemolytic disease of newborn, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 791, 793, with relative weights from 4.0590 to 4.1696 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of P55.9?

Under the General Equivalence Mappings, hemolytic disease of newborn, unspecified converts to ICD-9-CM 773.2 (NB hemolyt dis-isoim NEC). The mapping is approximate, so confirm the match fits the documentation.

What HCC is P55.9?

P55.9 (hemolytic disease of newborn, unspecified) maps to CMS-HCC Category 109 (Acquired Hemolytic, Aplastic, and Sideroblastic Anemias), commonly written as HCC 109, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It does not map to any RxHCC in the Part D prescription drug model.

Does P55.9 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, P55.9 adds a risk adjustment factor of about 1.144 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.529 to 1.815 depending on the payment segment). HCC 109 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 109 category page.