R63.6 Underweight

Billable ICD-10-CM code, FY2026.

Excludes1 (never code together)

• abnormal weight loss (R63.4)
• anorexia nervosa (F50.0-)
• malnutrition (E40-E46)

Use additional code

• code to identify body mass index (BMI), if known (Z68.-)

Applies from R63 Symptoms and signs concerning food and fluid intake

Excludes1 (never code together)

• bulimia NOS (F50.2-)

MS-DRG index

Defines the logic of DRG(s) 640-641 in MDC 10.

Approximate ICD-9-CM (GEMs)

• 783.22 Underweight

Diagnosis Index entries for R63.6

• Underweight

Nearby codes

• R63.31 Pediatric feeding disorder, acute
• R63.32 Pediatric feeding disorder, chronic
• R63.39 Other feeding difficulties
• R63.4 Abnormal weight loss
• R63.5 Abnormal weight gain
• R63.6 Underweight (this code)
• R63.8 Other symptoms and signs concerning food and fluid intake