ICD-10 Code J45.21 – Mild intermittent asthma with (acute) exacerbation (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code J45.21 – Mild intermittent asthma with (acute) exacerbation
What it is
J45.21 identifies mild intermittent asthma that has worsened into an acute flare. Use it when the record supports both the asthma severity pattern and a current exacerbation.
Clinical signs
Typical findings include wheezing, cough, chest tightness, and shortness of breath during an asthma flare. Clinical features vary; refer to documentation for the severity pattern and whether the episode is acute.
When to use this code
Use this code when the clinician documents mild intermittent asthma and notes an acute exacerbation, attack, or flare. It also fits encounters for worsening asthma symptoms requiring evaluation, as long as the severity classification is stated. If the chart does not specify mild intermittent asthma, check documentation.
Do not use for
Do not use this code for asthma without an exacerbation, or when a different asthma severity is documented. If the record only says asthma or the severity is unclear, check documentation.
Coding tip
Code both the asthma type and the acute exacerbation only when the provider clearly documents both elements.