ICD-10-CM 2027
ICD-10 code for defective circulation
From the official ICD-10-CM alphabetic index entry “Circulation › defective (lower extremity)”. Page updated September 29, 2026.
About coding defective circulation
The ICD-10-CM code for defective circulation is I99.9 (Unspecified disorder of circulatory system). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on I99.9.
Within I99, choose I99.9 (Unspecified disorder of circulatory system) only when documentation doesn't support a more specific option: other disorder of circulatory system (I99.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 302 (Atherosclerosis with MCC, relative weight 1.1984) and DRG 303 (Atherosclerosis without MCC, relative weight 0.6612), in MDC 05 (Diseases and Disorders of the Circulatory System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific defective circulation codes (official index)
- congenital Q28.9 — Congenital malformation of circulatory system, unspecified
Common questions about defective circulation ICD-10 codes
What is the ICD-10 code for defective circulation?
- I99.9 — Unspecified disorder of circulatory system. More specific codes apply when the documentation supports them: Q28.9.
What is the ICD-10 code for congenital defective circulation?
- Q28.9 — Congenital malformation of circulatory system, unspecified.
Is I99.9 billable?
- Yes. I99.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can I99.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict I99.9 as a principal diagnosis.
Is I99.9 a CC or MCC?
- No. I99.9 is neither a CC nor an MCC under MS-DRG v44.0.