Hello George, Thank you for posting your question on HCM, Low blood pressure is defined primarily by signs and symptoms of low blood flow and not by a specific blood pressure number. Some individuals routinely may have blood pressure numbers of 90/50 with no symptoms and therefore do not have low blood pressure. However, others who normally have higher blood pressures may develop symptoms of low blood pressure if their blood pressure drops to 100/60 People who have lower blood pressures have a lower risk of stroke, kidney disease, and heart disease. Athletes, people who exercise regularly, people who maintain ideal body weight, and nonsmokers tend to have lower blood pressures. Low blood pressure is desirable as long as it is not low enough to cause symptoms and damage to the organs in the body. The development of lightheadedness, dizziness, or fainting upon standing caused by low blood pressure is called orthostatic hypotension. Main causes of low blood pressure with symptoms can be dehydration, moderate od sever bleeding, sever inflammation of organs in the body, a slow heart rate, some medications, ect. If you know that you are a healthy person, who does regular check-ups to his doctor, then the most common cause may be dehydration. Your doctor will do the test for the orthostatic hypotension, which is the first step for diagnosing it. Then other labs that may be done are a complete blood count to rule our anemia, electrolytes levels to check the kidneys clearance, ect. According to your detailed history, and other symptoms you may have, your doctor will need to decide which is necessary to be done, and which cause can be ruled out. I would say, that 1 episode is not a problem. Keep in mind to be well hydrated, eat a healthy diet, avoid smoking and alcohol. If after these measures, it happens more often and becomes a problem, then seek a doctor advise, so he does the tests necessary to decide the cause of low blood pressure. Hope this helps, Take care. Dr. Klarida