A secondary diagnosis is any condition that co-exists with the primary condition at the time of the patient's admission. For example, if a patient is admitted with a primary diagnosis of heart failure and also has diabetes, diabetes would be considered a secondary diagnosis. A secondary diagnosis refers to a co-existing condition that could exist at the time the patient is admitted. This condition may evolve over the course of the patient's stay or may be a reason for additional treatment.
Like the primary diagnosis, secondary diagnoses are a key component of medical claims and provider billing. According to the ICD-10-CM guidelines, a secondary diagnostic code cannot be the only diagnosis billed in a claim. Therefore, services that are notified with a secondary diagnostic code as the only diagnosis in the claim will be rejected.
