E51.9 Thiamine deficiency, unspecified

The ICD-10-CM code for Thiamine deficiency, unspecified is E51.9 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

4: Endocrine, nutritional and metabolic diseases (E00-E89)

Section

E50-E64: Other nutritional deficiencies (E50-E64)

Category E51

7 codes (5 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to E51.9:

• Aneurin deficiency
• Thiamin deficiency
• Deficiency, deficient › aneurin
• Deficiency, deficient › thiamin, thiaminic (chloride)
• Deficiency, deficient › vitamin (multiple) NOS › thiamin
• Deficiency, deficient › vitamin (multiple) NOS › B1 NOS

U.S. Hospital Utilization

• An estimated 11,955 U.S. inpatient stays in 2023 included E51.9 among the documented diagnoses.
• 160 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Diabetes mellitus (TOC entry)

a. Diabetes mellitus ................................................................................................................... 39

Obesity (TOC entry)

b. Obesity .................................................................................................................................. 42

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)