Headache is one of the most complex and demanding areas of clinical practice. The challenge is to understand the pathophysiology, achieve an accurate diagnosis, and offer useful remedies. Headache and facial pain are two of the most common medical complains of mankind.Pain management is not part of the routine training for most physicians, yet the majority of patients seek medical attention because they have pain. Pain is typically addressed by primary care practitioners on an acute, time-limited basis, but when first- and second-level strategies fail, patients are referred to pain specialists and/or disease or body system specialists for more thorough evaluation and management.But, we should take care in the collection, handling, storage, and analysis of blood samples to decrease degree of error in ammonia levels.