Final answer:
The patient should avoid vitamin C for 72 hours before starting the test.
Step-by-step explanation:
For the patient in question, the instruction would be Option 4: Avoid vitamin C for 72 hours before starting the test. This is because vitamin C can interfere with the test and affect the results. By avoiding vitamin C, the patient can ensure accurate test outcomes. It is important to follow this instruction to obtain reliable results and facilitate proper medical evaluation.