A36.9 ICD-10-CM Code: Diphtheria, unspecified
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other bacterial diseases (A30-A49)
A36.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceDiphtheria, unspecified
Diphtheria is a serious bacterial infection caused by Corynebacterium diphtheriae that typically affects the throat and can produce a thick, grayish membrane that blocks the airway. This code is used when diphtheria is diagnosed but the specific type or affected site is not documented.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for A36.9 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A36.9 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A36.9 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A36.9 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A36.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A36.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A36.9 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is A36.9 an HCC code?
No. A36.9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A36.9 is the ICD-10-CM diagnosis code for diphtheria, unspecified. Diphtheria is a serious bacterial infection caused by Corynebacterium diphtheriae that typically affects the throat and can produce a thick, grayish membrane that blocks the airway. This code is used when diphtheria is diagnosed but the specific type or affected site is not documented. A36.9 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).
A36.9 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
If the documentation specifies the site of diphtheria (respiratory, cutaneous, etc.), use a more specific code (A36.0-A36.8) rather than the unspecified code A36.9.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A36.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •If the documentation specifies the site of diphtheria (respiratory, cutaneous, etc.), use a more specific code (A36.0-A36.8) rather than the unspecified code A36.9
- •Diphtheria is a reportable disease in most jurisdictions; verify that appropriate public health reporting requirements are met when coding this diagnosis