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ICD-10-CM 2027 diagnosis code

B99.9Unspecified infectious disease

✓ Billable / specific

B99.9 is a valid, billable ICD-10-CM code for unspecified infectious disease. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Infection.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About B99.9

B99.9 is the ICD-10-CM diagnosis code for unspecified infectious disease. It belongs to category B99 (other and unspecified infectious diseases), block B99 (other infectious diseases) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within B99, choose B99.9 (Unspecified infectious disease) only when documentation doesn't support a more specific option: other infectious disease (B99.8).

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 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235) and DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 136.9 (unspecified infectious and parasitic diseases).

Notes that apply from higher levels

Instructions written at a parent level also apply to B99.9.

Broader instructions also apply from Chapter 1: Certain infectious and parasitic diseases.

Alphabetic index entries

5 entries

Terms in the official ICD-10-CM index that lead to B99.9.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 136.9Unspecified infectious and parasitic diseasesapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about B99.9

Is B99.9 billable?

Yes. B99.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can B99.9 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict B99.9 as a principal diagnosis.

Is B99.9 a CC or MCC?

No. B99.9 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does B99.9 group to?

B99.9 is used in the MS-DRG v44.0 logic for MS-DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC), MS-DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC) and MS-DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for B99.9?

The CMS General Equivalence Mappings map B99.9 to ICD-9-CM 136.9.