What is ICD-10 code D55.9?

D55.9 is the ICD-10-CM diagnosis code for Anemia due to enzyme disorder, unspecified. A type of anemia caused by an enzyme disorder, but the specific enzyme deficiency has not been identified or documented. This is a placeholder code when the exact cause is unknown. D55.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. D55.9 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. D55.9 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. D55.9 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does D55.9 map to under V28?

D55.9 has no payable CMS-HCC V28 mapping in the final FY2026 CMS file.

What RAF reference is published for D55.9?

D55.9 has no V28 reference coefficient because the final FY2026 source verifies no payable V28 mapping.

What is the V28 vs V24 difference for D55.9?

D55.9 has verified no payable V28 mapping in the final FY2026 source. Select a historical effective period before making any V24 comparison.

What documentation supports D55.9?

This is the least specific code in the D55 category; use only when the specific enzyme disorder cannot be determined Query the provider to obtain more specific diagnosis if possible to allow for more precise coding D55.9 is not a CMS-HCC V28 payment code in the verified current source, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

2026 ICD-10-CM D55.9: Anemia due to enzyme disorder

D55.9 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupD55.9

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) / Hemolytic anemias (D55-D59)

D55.9

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Anemia due to enzyme disorder, unspecified

A type of anemia caused by an enzyme disorder, but the specific enzyme deficiency has not been identified or documented. This is a placeholder code when the exact cause is unknown.

Buddy Insight

This unspecified code is used when hemolytic anemia is attributed to an enzyme disorder but the specific enzyme deficiency has not been identified or documented.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 48

Coagulation Defects and Other...

Code-level coefficient reference

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

D55Anemia due to enzyme disorders D55.9Anemia due to enzyme disorder, unspecified

Inclusion Terms

Official

No inclusion terms are included in this display for D55.9. Check the code and parent instructions in the Code Book.

Excludes 2

Official

autoimmune disease (systemic) NOS (M35.9)Inherited from D50-D89
certain conditions originating in the perinatal period (P00-P96)Inherited from D50-D89
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from D50-D89
congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from D50-D89
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from D50-D89
human immunodeficiency virus [HIV] disease (B20)Inherited from D50-D89
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from D50-D89
neoplasms (C00-D49)Inherited from D50-D89
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from D50-D89

Related Codes

Official

D55.0Anemia due to glucose-6-phosphate dehydrogenase [G6PD] deficiency D55.1Anemia due to other disorders of glutathione metabolism D55.2Anemia due to disorders of glycolytic enzymes D55.3Anemia due to disorders of nucleotide metabolism D55.8Other anemias due to enzyme disorders

Includes

Official

No Includes notes are included in this display for D55.9. Check the code and parent instructions in the Code Book.

Excludes 1

Official

drug-induced enzyme deficiency anemia (D59.2)Inherited from D55

Code First

Official

No Code First sequencing instructions are included in this display for D55.9. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for D55.9. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for D55.9. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documentation should include the basis for suspecting an enzyme disorder (e.g., chronic hemolysis with negative Coombs test, family history), results of any enzyme assays performed, and the reason why a more specific enzyme cannot be identified.

Record hemoglobin levels, reticulocyte counts, and management plan.

A provider query should be initiated to obtain additional specificity whenever possible.

MEAT Support

HCC Buddy guidance

Record hemoglobin levels, reticulocyte counts, and management plan.

A provider query should be initiated to obtain additional specificity whenever possible.

Audit Caution

HCC Buddy guidance

This is the least specific code in the D55 series and should only be used when more specific information cannot be obtained. No V28 HCC mapping exists for this code. Always query the provider for the specific enzyme disorder before assigning D55.

Avoid using this code long-term -- repeated encounters should prompt additional diagnostic workup to achieve more specific classification.

Common Mistakes

HCC Buddy guidance

D55.9 vs. D55.8 (Other anemias due to enzyme disorders) -

use D55.8 when the enzyme disorder is identified but does not fit a specific subcategory, vs. D55.9 when completely unknown. D55.9 vs. D58.9 (Hereditary hemolytic anemia, unspecified) -

D58.9 covers all hereditary hemolytic anemias unspecified, not limited to enzyme defects. D55.9 vs. D59.9 (Acquired hemolytic anemia, unspecified) -

ensure the disorder is documented as inherited, not acquired.

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is D55.9 an HCC code?

D55.9 is not in the CMS-HCC V28 or V24 community payment model. D55.9 has a separate mapping under the CMS-HCC ESRD model (HCC 48 (Coagulation Defects and Other Specified Hematological Disorders)); the applicable result needs member context.

Code: D55.9
Description: Anemia due to enzyme disorder, unspecified
HCC (V28): No CMS-HCC V28 mapping
RAF reference coefficient: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

ESRDHCC 48, Coagulation Defects and Other Specified Hematological Disorders

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work D55.9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D55.9

For D55.9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

D55.9 is the ICD-10-CM diagnosis code for anemia due to enzyme disorder, unspecified. A type of anemia caused by an enzyme disorder, but the specific enzyme deficiency has not been identified or documented. This is a placeholder code when the exact cause is unknown. D55.9 sits in the ICD-10-CM chapter for diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89), within the section covering hemolytic anemias (d55-d59).

D55.9 has no mapping under the CMS-HCC V28 or V24 community payment models. D55.9 has a separate mapping under the CMS-HCC ESRD model (HCC 48 (Coagulation Defects and Other Specified Hematological Disorders)); the applicable result needs member context. Do not assign V28 risk adjustment value from this page; verify the applicable model and payment year before using this code for risk adjustment.

This is the least specific code in the D55 category; use only when the specific enzyme disorder cannot be determined.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for D55.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is the least specific code in the D55 category; use only when the specific enzyme disorder cannot be determined
•Query the provider to obtain more specific diagnosis if possible to allow for more precise coding

Clinical Significance

This unspecified code is used when hemolytic anemia is attributed to an enzyme disorder but the specific enzyme deficiency has not been identified or documented. It represents the least specific code in the D55 category and should prompt a query to the provider for additional diagnostic workup. The clinical impact of unspecified enzyme disorders varies widely, making accurate classification important for appropriate management and risk stratification.

Documentation Requirements

✓Documentation should include the basis for suspecting an enzyme disorder (e.g., chronic hemolysis with negative Coombs test, family history), results of any enzyme assays performed, and the reason why a more specific enzyme cannot be identified.
✓Record hemoglobin levels, reticulocyte counts, and management plan.
✓A provider query should be initiated to obtain additional specificity whenever possible.

Commonly Confused Codes

•D55.9 vs. D55.8 (Other anemias due to enzyme disorders) -
•use D55.8 when the enzyme disorder is identified but does not fit a specific subcategory, vs. D55.9 when completely unknown. D55.9 vs. D58.9 (Hereditary hemolytic anemia, unspecified) -
•D58.9 covers all hereditary hemolytic anemias unspecified, not limited to enzyme defects. D55.9 vs. D59.9 (Acquired hemolytic anemia, unspecified) -
•ensure the disorder is documented as inherited, not acquired.