There are several types of hypotension. People who always have low blood pressure have chronic asymptomatic hypotension. They have no signs or symptoms and need no treatment. Their low blood pressure is normal for them.
The three main types of this kind of hypotension are orthostatic hypotension, neurally mediated hypotension (NMH), and severe hypotension linked to shock.
This type of low blood pressure occurs when standing up from a sitting or lying down position. It can make you feel dizzy or lightheaded, or even make you faint.
Orthostatic hypotension occurs if your body isn't able to adjust blood pressure and blood flow fast enough for the change in position. This type of low blood pressure usually lasts for only a few seconds or minutes after you stand up. You may need to sit or lie down for a short time while your blood pressure returns to normal.
Orthostatic hypotension can occur in all age groups. However, it's more common in older adults, especially those who are frail or in poor health. It can be a symptom of other medical conditions, and treatment often focuses on treating the underlying condition(s).
Neurally mediated hypotension
With NMH, blood pressure drops after you've been standing for a long time. You may feel dizzy, faint, or sick to the stomach as a result. This type of low blood pressure also can occur if you have an unpleasant, upsetting, or scary experience.
Severe Hypotension Linked to Shock
People may say a person has "gone into shock" as a result of an upsetting event. But to doctors, the word "shock" has a different meaning. This implies collapse of the cardiovascular system from a variety of reasons.
This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.