E51.9
Thiamine deficiency, unspecified
E51.9 (also written E519) is a billable ICD-10-CM diagnosis code for thiamine deficiency, unspecified. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 5 codes in category E51 (Thiamine deficiency). The Alphabetic Index lists it under 6 entries. Its coding notes include 2 Excludes1 entries and 1 Excludes2 entry.
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Other clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 34 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CNotes
Also from chapter/block level (1 note)
- All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 6 entries