Question: Can you explain the difference between "diagnostic" and "therapeutic" injections or nerve blocks? How does the provider decide which to do? Answer: Physicians use diagnostic nerve blocks to determine sources of the patient's pain. These blocks typically contain an anesthetic with a known duration of relief. Therapeutic nerve blocks contain local anesthetic to control acute pain, once the physician confirms the source and cause of discomfort. Most CPT section heads for injection or nerve block codes mention "diagnostic or therapeutic." The codes often cover both situations, which means you could possibly report the same code for both diagnostic and therapeutic injections, based on the type of block and administration site. Example: