Skip to content
HCC Buddy home

A64 ICD-10-CM Code: Unspecified sexually transmitted disease

A64 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.

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Infections with a predominantly sexual mode of transmission (A50-A64)

A64

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

Unspecified sexually transmitted disease

This code is used when a patient has a sexually transmitted infection, but the specific type has not been identified or documented. It serves as a placeholder diagnosis when the exact STI is unknown or testing results are pending.

CMS-HCC V28

N/A

—

Not mapped

CMS-HCC V24

N/A

—

Not mapped

ACA/HHS

N/A

—

Not mapped

ESRD/PACE

N/A

—

Not mapped

RXHCC

N/A

—

Not mapped

Code Book Path

Official
A6Infections with a predominantly sexual mode of transmission (A50-A64)
A64Unspecified sexually transmitted disease

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for A64 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for A64 in this effective period.

Related Child Codes

Official

ICD-10-CM does not list child codes under A64 for this display context.

Includes

Official

ICD-10-CM does not list Includes notes for A64 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for A64 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for A64 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for A64 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A64 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Use this code only when the specific STI cannot be determined; always attempt to identify the causative organism through testing and documentation before assigning this unspecified code
Review the medical record for any test results, cultures, or provider notes that might specify the type of STI, as using a more specific code improves clinical clarity and treatment tracking

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 A64 an HCC code?

No. A64 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

Code
A64
Description
Unspecified sexually transmitted disease
HCC (V28)
No CMS-HCC V28 mapping
RAF reference coefficient
—
Billable
Yes
Payment year
2026

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.

This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).

What This Code Means

A64 is the ICD-10-CM diagnosis code for unspecified sexually transmitted disease. This code is used when a patient has a sexually transmitted infection, but the specific type has not been identified or documented. It serves as a placeholder diagnosis when the exact STI is unknown or testing results are pending. A64 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering infections with a predominantly sexual mode of transmission (a50-a64).

A64 is a billable ICD-10-CM code, but the current payload does not show a mapping under the CMS-HCC V28, V24, ESRD, or RxHCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.

Use this code only when the specific STI cannot be determined; always attempt to identify the causative organism through testing and documentation before assigning this unspecified code.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for A64 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use this code only when the specific STI cannot be determined; always attempt to identify the causative organism through testing and documentation before assigning this unspecified code
  • •Review the medical record for any test results, cultures, or provider notes that might specify the type of STI, as using a more specific code improves clinical clarity and treatment tracking

Code Hierarchy

└A64Unspecified sexually transmitted disease
└A64Unspecified sexually transmitted disease

Work A64 in HCC Buddy

Open A64 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