Skip to content
HCC Buddy home

D66 ICD-10-CM Code: Hereditary factor VIII deficiency

D66 maps to CMS-HCC V28 111. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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 lookupD66

FY 2026 Apr update / Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) / Coagulation defects, purpura and other hemorrhagic conditions (D65-D69)

D66

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

Hereditary factor VIII deficiency

A hereditary bleeding disorder caused by deficiency or dysfunction of clotting factor VIII, commonly known as hemophilia A.

Buddy the Bee presenting code insight

Buddy Insight

Hereditary factor VIII deficiency (Hemophilia A) is the most common severe inherited bleeding disorder, caused by deficient or defective clotting factor VIII.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 111

Coefficient HCC 111: 4.639 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

Context needed

HCC 066, HCC 075

Coefficient needs member context

ESRD/PACE

Context needed

HCC 46, HCC 48

Coefficient needs member context

RXHCC

N/A

—

Not mapped

Code Book Path

Official
D6Coagulation defects, purpura and other hemorrhagic conditions (D65-D69)D66Hereditary factor VIII deficiency

Inclusion Terms

Official
  • Classical hemophilia
  • Deficiency factor VIII (with functional defect)
  • Hemophilia NOS
  • Hemophilia A

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

No related codes are included in this display for D66. Check the Code Book for the complete code path.

Includes

Official

No Includes notes are included in this display for D66. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • factor VIII deficiency with vascular defect (D68.0-)

Code First

Official

No Code First sequencing instructions are included in this display for D66. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for D66. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for D66. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Document the severity level (severe, moderate, mild) based on factor VIII activity levels.
Record current treatment regimen including factor replacement products, dosing frequency, and whether the patient has developed inhibitors (antibodies to factor VIII).
Note any target joints, history of intracranial hemorrhage, and hepatitis/HIV status if applicable from prior blood product exposure.

MEAT Support

HCC Buddy guidance
Document the severity level (severe, moderate, mild) based on factor VIII activity levels.
Record current treatment regimen including factor replacement products, dosing frequency, and whether the patient has developed inhibitors (antibodies to factor VIII).
Note any target joints, history of intracranial hemorrhage, and hepatitis/HIV status if applicable from prior blood product exposure.

Audit Caution

HCC Buddy guidance
Do not confuse hereditary hemophilia A (D66) with acquired hemophilia (D68.311), which has a fundamentally different etiology and treatment approach.
Ensure documentation specifies factor VIII deficiency versus factor IX to distinguish from Hemophilia B (D67).
If the patient has developed inhibitors, also code D68.311 if appropriate.

Common Mistakes

HCC Buddy guidance
D67 (Hereditary factor IX deficiency/Hemophilia B) — clinically similar but different factor deficiency requiring different replacement products
D68.311 (Acquired hemophilia) — autoimmune condition developing later in life with autoantibodies against factor VIII
D68.00-D68.09 (Von Willebrand disease) — may have low factor VIII but primary defect is in von Willebrand factor.

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 D66 an HCC code?

Yes. D66 (Hereditary factor VIII deficiency) maps to HCC 111, Hemophilia, Male under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 4.639. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: D66 is billable and maps to V28 HCC 111, Hemophilia, Male. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
D66
Description
Hereditary factor VIII deficiency
HCC (V28)
HCC 111 — Hemophilia, Male
RAF reference coefficient
4.639
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 111, Hemophilia, Male
4.639

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 D66 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D66

For D66, 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

D66 is the ICD-10-CM diagnosis code for hereditary factor viii deficiency. A hereditary bleeding disorder caused by deficiency or dysfunction of clotting factor VIII, commonly known as hemophilia A. D66 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 coagulation defects, purpura and other hemorrhagic conditions (d65-d69).

Under the CMS-HCC V28 risk adjustment model, D66 maps to Hemophilia, Male (HCC 111) with a source-labeled community, non-dual, aged reference coefficient of 4.639. No V24 mapping is shown for D66; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Specify the severity level (mild, moderate, severe) if documented. For D66, 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. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for D66 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Specify the severity level (mild, moderate, severe) if documented
  • •Use additional codes for any complications such as inhibitor development

Clinical Significance

Hereditary factor VIII deficiency (Hemophilia A) is the most common severe inherited bleeding disorder, caused by deficient or defective clotting factor VIII. Severity correlates with factor VIII activity levels: severe (<1%), moderate (1-5%), or mild (5-40%).

Documentation Requirements

  • ✓Document the severity level (severe, moderate, mild) based on factor VIII activity levels.
  • ✓Record current treatment regimen including factor replacement products, dosing frequency, and whether the patient has developed inhibitors (antibodies to factor VIII).
  • ✓Note any target joints, history of intracranial hemorrhage, and hepatitis/HIV status if applicable from prior blood product exposure.

Excludes 1, Do NOT code together

  • factor VIII deficiency with vascular defect (D68.0-)

Commonly Confused Codes

  • •D67 (Hereditary factor IX deficiency/Hemophilia B): clinically similar but different factor deficiency requiring different replacement products
  • •D68.311 (Acquired hemophilia): autoimmune condition developing later in life with autoantibodies against factor VIII
  • •D68.00-D68.09 (Von Willebrand disease): may have low factor VIII but primary defect is in von Willebrand factor.

Code Hierarchy

└D66Hereditary factor VIII deficiency
└D66Hereditary factor VIII deficiency

For D66, 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.

D66 maps to CMS-HCC V28 category 111, Hemophilia, Male. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for D66. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

Work D66 in HCC Buddy

Open D66 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro