Underdosing of unsp drug/meds/biol subst, sequela

This code signifies a long-term consequence or complication arising from a patient receiving less than the prescribed or recommended dosage of an unspecified medication, drug, or biological substance. It indicates that the underdosing event itself is no longer active, but its lasting effects are still being addressed.

Use this code when documenting a condition or symptom that is a direct result of a past underdosing incident, and the underdosing itself is no longer occurring. Examples include chronic organ damage, persistent neurological deficits, or ongoing disease progression directly attributable to insufficient medication intake in the past.

• This code should only be used as a secondary diagnosis, following the code for the specific condition or symptom that is the sequela.
• Ensure documentation clearly links the current condition to a previous underdosing event of an unspecified substance.
• Avoid using this code if the underdosing is still active; instead, use the appropriate acute underdosing code (e.g., T50.906A, T50.906D).