ICD-10 Code E51 – Thiamine deficiency (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E51 – Thiamine deficiency
What it is
E51 identifies thiamine (vitamin B1) deficiency. Use it when the record documents inadequate thiamine status, whether from poor intake, malabsorption, or increased need.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include weakness, neuropathy, confusion, and other signs of nutritional deficiency or neurologic involvement.
When to use this code
Use E51 when the provider diagnoses thiamine deficiency or documents a thiamine-deficiency disorder. It is appropriate for confirmed deficiency in malnutrition, alcohol-related deficiency, or other causes when thiamine is the stated problem. If the note only suggests possible deficiency, check documentation before coding.
Do not use for
Do not use E51 for nonspecific malnutrition without documented thiamine deficiency. Also avoid it when the chart names a different vitamin deficiency or only lists screening, risk, or history.
Coding tip
Code E51 only when thiamine deficiency is explicitly documented; if the record is vague, query for clarification.