ICD-10-CM 2027 diagnosis code

I99Other and unspecified disorders of circulatory system

Not billable — use a more specific code

I99 is a header code, so it can't be reported by itself. Choose one of the 2 more specific codes beneath it.

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 I99

I99 is the ICD-10-CM diagnosis code for other and unspecified disorders of circulatory system. It belongs to block I95-I99 (other and unspecified disorders of the circulatory system) and chapter 9 (diseases of the circulatory system). It is a header code, so it can't be reported by itself; one of its 2 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: I99.8 (system) and I99.9 (system).

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

Specific codes under I99

Notes that apply from higher levels

Instructions written at a parent level also apply to I99.

Broader instructions also apply from Chapter 9: Diseases of the circulatory system.

Code history

2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about I99

Is I99 billable?: No. I99 is a header code. Report one of its more specific subcodes instead.