ICD-10 Code G12.21 – Amyotrophic lateral sclerosis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G12.21 – Amyotrophic lateral sclerosis
What it is
Amyotrophic lateral sclerosis is a progressive motor neuron disease that causes degeneration of upper and lower motor neurons. It leads to worsening weakness and loss of voluntary muscle control.
Clinical signs
Typical findings include muscle weakness, atrophy, fasciculations, spasticity, and brisk reflexes. Clinical features vary; refer to documentation.
When to use this code
Use G12.21 when the provider documents ALS, Lou Gehrig disease, or amyotrophic lateral sclerosis as the diagnosis. Apply it for confirmed disease in outpatient, inpatient, or problem-list documentation when the condition is being managed or evaluated. Check documentation if the note only suggests a motor neuron disorder.
Do not use for
Do not use this code for other motor neuron diseases, muscular dystrophy, or nonspecific generalized weakness. If the record does not clearly identify ALS, check documentation.
Coding tip
Code the documented term exactly; if the note says ALS, G12.21 is the correct choice.