ICD-10-CM 2027 diagnosis code
K63.821Small intestinal bacterial overgrowth
K63.821 is a header code, so it can't be reported by itself. Choose one of the 3 more specific codes beneath it.
Code last changed in FY2024 (effective October 1, 2023). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About K63.821
K63.821 is the ICD-10-CM diagnosis code for small intestinal bacterial overgrowth. It belongs to category K63 (other diseases of intestine), block K55-K64 (other diseases of intestines) and chapter 11 (diseases of the digestive system). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.
Within K63.82 (intestinal microbial overgrowth), K63.821 is specifically for small intestinal bacterial overgrowth. Related codes cover small intestinal fungal overgrowth (K63.822) and intestinal methanogen overgrowth, unspecified (K63.829).
To report this condition, pick the subcode that matches the documentation: K63.8211 (hydrogen-subtype), K63.8212 (hydrogen sulfide-subtype) and K63.8219 (unspecified).
It was added in FY2024, effective October 1, 2023.
Specific codes under K63.821
Notes that apply from higher levels
Instructions written at a parent level also apply to K63.821.
Broader instructions also apply from Chapter 11: Diseases of the digestive system.
Code history
- 2016
- 2017
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- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2024 (effective 10/1/2023): Added
- No changes since FY2024.
Common questions about K63.821
Is K63.821 billable?
- No. K63.821 is a header code. Report one of its more specific subcodes instead.