Hypotension occurs when blood pressure drops below the normal range. Doctors generally define low blood pressure as 90/60 mm Hg or below, commonly said as “90 over 60” Usually, doctors only treat hypotension if it is severe enough to cause symptoms.
Orthostatic hypotension: People with orthostatic hypotension (sometimes called postural hypotension) feel faint or lightheaded when they stand up or change position suddenly.
Postprandial hypotension: This condition causes people to feel lightheaded or dizzy after eating a meal because their blood pressure drops suddenly.
Neurally mediated hypotension: People with this disorder feel faint, dizzy, and nauseous after exercising or standing for a long time.
Severe hypotension linked to shock: Shock is the most extreme form of hypotension. When a person is in shock, blood pressure drops to dangerously low levels, and the brain and organs can’t get enough blood to function.
A blood pressure reading lower than 90 millimeters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic) is generally considered low blood pressure.
The causes of low blood pressure can range from dehydration to serious medical disorders. It’s important to find out what’s causing your low blood pressure so that it can be treated.
Optimal blood pressure is less than 120/80 (systolic/diastolic). In healthy people, low blood pressure without any symptoms is not usually a concern and does not need to be treated. But low blood pressure can be a sign of an underlying problem — especially in the elderly — where it may cause inadequate blood flow to the heart, brain, and other vital organs.
The basics on low blood pressure from WebMD.Chronic low blood pressure with no symptoms is almost never serious. But health problems can occur when blood pressure drops suddenly and the brain is deprived of an adequate blood supply. This can lead to dizziness or lightheadedness. Sudden drops in blood pressure most commonly occur in someone who’s rising from a lying down or sitting position to standing. This kind of low blood pressure is known as postural hypotension or orthostatic hypotension. Another type of low blood pressure can occur when someone stands for a long period of time. This is called neurally mediated hypotension.
For some people, low blood pressure signals an underlying problem, especially when it drops suddenly or is accompanied by signs and symptoms such as:
Dizziness or lightheadedness
Blurred or fading vision
Lack of concentration
Sudden drops in blood pressure can be life-threatening. Causes of this type of hypotension include:
Loss of blood from bleeding
Low body temperature
High body temperature
Heart muscle disease causing heart failure
Sepsis, a severe blood infection
Severe dehydration from vomiting, diarrhea, or fever
A reaction to medication or alcohol
A severe allergic reaction called anaphylaxis that causes an irregular heartbeat
Even occasional dizziness or lightheadedness may be a relatively minor problem — the result of mild dehydration from too much time in the sun or a hot tub, for example. Still, it’s important to see your doctor if you have signs or symptoms of low blood pressure because they can point to more-serious problems. It can be helpful to keep a record of your symptoms, when they occur and what you’re doing at the time.