2027 ICD-10-CM Diagnosis Code D66Hereditary factor VIII deficiency
ICD-10-CM Codes›D50–D89›D65-D69›D66
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 111
- Chronic Condition
D66 is a billable ICD-10-CM diagnosis code for hereditary factor VIII deficiency. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 813. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 51 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Coagulation and hemorrhagic disorders.
For Medicare Advantage risk adjustment, D66 maps to CMS-HCC Category 111 (Hemophilia, Male) under the V28 model, adding a risk factor of about 4.639 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
D66 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 2027.
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.
- Combined deficiency of factor V and factor VIII
- Factor V deficiency
- Factor VIII deficiency
- Hemophilia
- Hemophilic arthropathy of bilateral ankles
- Hemophilic arthropathy of bilateral elbows
- Hemophilic arthropathy of bilateral hips
- Hemophilic arthropathy of bilateral knees
- Hemophilic arthropathy of bilateral shoulders
- Hemophilic arthropathy of bilateral wrists
- Hemophilic arthropathy of left ankle
- Hemophilic arthropathy of left elbow
- Hemophilic arthropathy of left hip
- Hemophilic arthropathy of left knee
- Hemophilic arthropathy of left shoulder
- Hemophilic arthropathy of left wrist
- Hemophilic arthropathy of right ankle
- Hemophilic arthropathy of right elbow
- Hemophilic arthropathy of right hip
- Hemophilic arthropathy of right knee
- Hemophilic arthropathy of right shoulder
- Hemophilic arthropathy of right wrist
- Hereditary combined coagulation factor deficiency
- Hereditary factor VIII deficiency disease
- Hereditary factor VIII deficiency disease with inhibitor
- Hereditary factor VIII deficiency disease without inhibitor
- Lamellar ichthyosis
- Mild hereditary factor VIII deficiency disease
- Mild hereditary factor VIII deficiency disease with high response inhibitor
- Mild hereditary factor VIII deficiency disease with inhibitor
- Mild hereditary factor VIII deficiency disease with low response inhibitor
- Mild hereditary factor VIII deficiency disease without inhibitor
- Moderate hereditary factor VIII deficiency disease
- Moderate hereditary factor VIII deficiency disease with high response inhibitor
- Moderate hereditary factor VIII deficiency disease with inhibitor
- Moderate hereditary factor VIII deficiency disease with low response inhibitor
- Moderate hereditary factor VIII deficiency disease without inhibitor
- Multiple sclerosis, ichthyosis, factor VIII deficiency syndrome
- Severe hereditary factor VIII deficiency disease
- Severe hereditary factor VIII deficiency disease with high response inhibitor
- Severe hereditary factor VIII deficiency disease with inhibitor
- Severe hereditary factor VIII deficiency disease with low response inhibitor
- Severe hereditary factor VIII deficiency disease without inhibitor
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to D66: its own notes plus those printed at Chapter 3. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Classical hemophilia
- Deficiency factor VIII (with functional defect)
- Hemophilia NOS
- Hemophilia A
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- factor VIII deficiency with vascular defect (D68.0-)
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.
- autoimmune disease (systemic) NOS (M35.9)
- certain conditions originating in the perinatal period (P00-P96)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- human immunodeficiency virus [HIV] disease (B20)
- 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)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name D66, its category, or a range that includes it.
Excludes1 2
These codes carry an Excludes1 note naming D66: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 1
These codes carry an Excludes2 note naming D66: its condition is not part of those codes, and both may be reported when the patient has both.
- Block R70-R79 Abnormal findings on examination of blood, without diagnosis
Code First 2
These codes say to code first a condition named in the note, and D66 is one of the conditions named.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Arthropathy See Also: Arthritis; M12.9
hemophilic NEC D66
hemophilia NEC D66
factor (A) D66
factor See Also: Deficiency, coagulation;
Disease, diseased See Also: Syndrome;
bleeder's D66
Subhemophilia D66
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Hemophilia A
the classic hemophilia resulting from a deficiency of factor viii. it is an inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhage.
Patient EducationClinical
Hemophilia
Hemophilia is a rare bleeding disorder in which the blood does not clot properly. This can lead to problems with bleeding too much after an injury or surgery. You can also have sudden bleeding inside your body, such as in your joints, muscles, and organs.
The full article covers:
- What is hemophilia?
- What are the types of hemophilia?
- What causes hemophilia?
- Who is at risk for hemophilia?
- What are the symptoms of hemophilia?
- How is hemophilia diagnosed?
- What are the treatments for hemophilia?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert D66 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About D66Overview
What is the ICD-10 code for hereditary factor VIII deficiency?
The ICD-10-CM code for hereditary factor VIII deficiency is D66. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is D66 (Hereditary factor VIII deficiency) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report hereditary factor VIII deficiency on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does D66 group to?
When hereditary factor VIII deficiency is the principal diagnosis on an inpatient stay, it groups to MS-DRG 813 (coagulation Disorders), which carries a relative weight of 1.5279. Higher weights mean higher Medicare reimbursement.
Is D66 a CC or MCC?
CMS lists D66 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 51 closely related codes in its exclusion list.
Can D66 be reported with a code from D68.0?
Not as a rule. The Excludes1 note on D66 lists "factor VIII deficiency with vascular defect (D68.0-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is D66?
D66 (hereditary factor VIII deficiency) maps to CMS-HCC Category 111 (Hemophilia, Male), commonly written as HCC 111, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 46 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does D66 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, D66 adds a risk adjustment factor of about 4.639 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 4.639 to 32.199 depending on the payment segment). HCC 111 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 111 category page.
