ICD-10-CM 2027
ICD-10 code for Underweight
From the official ICD-10-CM alphabetic index entry “Underweight”. Page updated September 29, 2026.
About coding Underweight
The ICD-10-CM code for Underweight is R63.6 (Underweight).
Within R63 (symptoms and signs concerning food and fluid intake), R63.6 is specifically for Underweight. Related codes cover Anorexia (R63.0), Polydipsia (R63.1), Polyphagia (R63.2), feeding difficulties (R63.3), abnormal weight loss (R63.4), abnormal weight gain (R63.5) and other symptoms and signs concerning food and fluid intake (R63.8).
Don't report R63.6 together with the conditions in its Excludes1 note: abnormal weight loss (R63.4), anorexia nervosa (F50.0-) and malnutrition (E40-E46).
Use an additional code to identify body mass index (BMI), if known (Z68.-).
More specific Underweight codes (official index)
- for gestational age
Don't confuse with (Excludes1 for R63.6)
Common questions about Underweight ICD-10 codes
What is the ICD-10 code for Underweight?
- R63.6 — Underweight.
Is R63.6 billable?
- Yes. R63.6 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can R63.6 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict R63.6 as a principal diagnosis.
Is R63.6 a CC or MCC?
- No. R63.6 is neither a CC nor an MCC under MS-DRG v44.0.