Final answer:
The follow-up visit is important to monitor the effectiveness of the treatment, assess for side effects, and make necessary adjustments to the treatment plan.
Step-by-step explanation:
The follow-up visit is important because it allows the veterinarian to monitor the effectiveness of the ketoconazole treatment and assess any potential side effects or complications. Blood work can provide valuable information about the dog's response to the medication and help guide further treatment decisions. For example, it can show if the dog's blastomycosis infection is improving, if the medication dosage needs adjustment, or if there are any changes in the dog's liver or kidney function that may require modifications to the treatment plan.