J45.90 is a "category code," which means it's non-billable. Billable codes require more specificity. Use the list below to navigate to codes that are more specific:
10
J45.901
Unspecified asthma with (acute) exacerbation
Billable
10
J45.902
Unspecified asthma with status asthmaticus
Billable
10
J45.909
Unspecified asthma, uncomplicated
Billable