D66 — Hereditary factor VIII deficiency

D66

ICD-10 Chapter 3: Blood & Immune Disorders — illustrative image — Chapter 3: Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50–D89) — illustrative image

What this code means

Haemophilia A is an inherited bleeding disorder caused by deficiency of clotting factor VIII.

Also called: hemophilia a, factor viii deficiency.

When this code is used

Used for hereditary factor VIII deficiency (haemophilia A).

Where it sits in ICD-10-CM

Code D66 belongs to Chapter 3: Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism, which covers codes D50–D89 in the FY2027 ICD-10-CM tabular list. The official description above is copied verbatim from the CDC/NCHS FY2027 code file.

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Frequently asked questions

What is ICD-10-CM code D66?

D66 is the ICD-10-CM diagnosis code for “Hereditary factor VIII deficiency”. Haemophilia A is an inherited bleeding disorder caused by deficiency of clotting factor VIII.

When is code D66 used?

Used for hereditary factor VIII deficiency (haemophilia A). It belongs to Chapter 3 of ICD-10-CM (Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism).

This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.