Low blood pressure, called hypotension, means the force of blood pushing through your arteries is lower than the typical range. A reading below 90/60 mm Hg is generally considered low. For many people, especially younger adults and those who are physically fit, low blood pressure causes no symptoms and is perfectly normal. It only becomes a concern when it drops low enough to reduce blood flow to your organs, causing symptoms like dizziness, fainting, or fatigue.
What the Numbers Mean
Blood pressure is recorded as two numbers. The top number (systolic) measures pressure when your heart beats. The bottom number (diastolic) measures pressure between beats. A normal reading is around 120/80 mm Hg. When either number dips below 90/60, the reading falls into low territory.
But context matters more than the number itself. Some people walk around with a systolic reading in the 80s and feel fine. What matters is whether the reading is lower than your personal baseline and whether you’re experiencing symptoms. A sudden drop from your usual range is more significant than a number that’s always been on the low side.
How Your Body Controls Blood Pressure
Blood pressure depends on two things: how much blood your heart pumps out with each beat (cardiac output) and how tightly your blood vessels are squeezing (vascular resistance). If either one falls, your blood pressure drops. This can happen in four main ways: your body loses fluid and blood volume drops, your heart can’t pump effectively, something blocks blood from filling the heart properly, or your blood vessels relax and widen too much. Most causes of low blood pressure trace back to one of these mechanisms.
Common Causes
Dehydration is one of the most frequent culprits. When you lose more fluid than you take in, whether from heat, exercise, vomiting, or diarrhea, your blood volume drops and pressure falls with it. Even mild dehydration on a hot day can trigger noticeable symptoms.
Heart conditions can also lower blood pressure. Heart failure, heart valve problems, a heart attack, and an unusually slow heart rate (bradycardia) all reduce the amount of blood the heart pushes out per beat.
Hormonal and metabolic conditions play a role too. Problems with the adrenal glands (such as Addison’s disease), low blood sugar, and diabetes can all interfere with the body’s ability to regulate pressure. Thyroid disorders fit into this category as well.
Nutritional deficiencies are an underappreciated cause. Low levels of vitamin B-12, folate, or iron prevent your body from making enough red blood cells, a condition called anemia. Fewer red blood cells means less oxygen-carrying capacity in the blood, which can lead to low pressure along with fatigue and weakness.
Certain medications are common triggers, particularly water pills (diuretics), blood pressure medications, some antidepressants, and drugs for erectile dysfunction. If your blood pressure dropped after starting a new medication, that’s worth flagging with your doctor.
Types of Low Blood Pressure
Not all low blood pressure behaves the same way. The type you have depends on when and why it happens.
Orthostatic hypotension is a drop that occurs when you stand up. It’s defined as a fall of at least 20 points in the top number or 10 points in the bottom number within three minutes of standing. You might feel lightheaded or see spots when getting out of bed or rising from a chair. It’s especially common in older adults and people on blood pressure medications.
Postprandial hypotension happens after eating. When you digest a large meal, blood flow shifts toward your digestive system. In some people, the body doesn’t compensate well enough, and pressure drops. This is most common in older adults and tends to be worse after carbohydrate-heavy meals.
Neurally mediated hypotension occurs when a miscommunication between the brain and heart causes a sudden, unexpected drop in pressure. This is the type behind vasovagal syncope, where you faint in response to triggers like prolonged standing, emotional stress, the sight of blood, or extreme heat. Unlike orthostatic hypotension, these episodes are sudden and unpredictable rather than consistently tied to standing up.
Symptoms to Recognize
When blood pressure is low enough to cause problems, the symptoms usually reflect reduced blood flow to the brain and other organs:
- Dizziness or lightheadedness, especially when standing
- Blurred vision
- Nausea
- Fatigue and general weakness
- Difficulty concentrating
- Fainting
If you have a low reading but none of these symptoms, your blood pressure is likely just naturally on the lower end. That’s not a medical problem.
When Low Blood Pressure Is Dangerous
In rare cases, blood pressure can drop severely enough to cause shock, a life-threatening condition where your organs aren’t getting the blood they need. Signs of shock include cold and clammy skin, rapid and shallow breathing, a weak but fast pulse, and confusion. Severe blood loss, serious infections (sepsis), and severe allergic reactions (anaphylaxis) can all cause this kind of extreme drop. This is a medical emergency.
Even outside of shock, repeated fainting from low blood pressure carries its own risks. Falls can cause fractures, head injuries, and other trauma, particularly in older adults.
How Low Blood Pressure Is Diagnosed
A single low reading doesn’t tell the full story. Your doctor will likely want to check your pressure at different times and in different positions: lying down, sitting, and standing. This positional testing is simple and can reveal orthostatic hypotension within minutes.
If the cause isn’t obvious, a tilt table test may be used. You lie on a padded table that’s quickly tilted from flat to upright while monitors track your blood pressure, heart rate, and rhythm. The test mimics standing and can help diagnose orthostatic hypotension, vasovagal syncope, and related conditions. Before ordering this test, providers typically rule out structural heart problems or irregular heart rhythms first.
Blood tests may also be ordered to check for anemia, thyroid problems, blood sugar issues, or nutritional deficiencies that could explain the drop.
Managing Low Blood Pressure Day to Day
If your low blood pressure is causing symptoms, the first line of defense is usually lifestyle changes rather than medication.
Staying well hydrated is the simplest and most effective step. Increasing fluid intake raises blood volume, which directly supports pressure. For people with orthostatic hypotension, a modest increase in salt intake is one of the first recommendations, since salt helps the body retain fluid. The key word is modest: large increases in dietary salt carry their own cardiovascular risks over time, and the long-term effects of high salt intake in people with low blood pressure haven’t been well studied.
Physical counterpressure maneuvers can help in the moment. Crossing your legs while standing, squeezing your thigh muscles, or clenching your fists can temporarily push blood pressure up when you feel symptoms coming on. Compression stockings serve a similar purpose by preventing blood from pooling in your legs.
Other practical habits make a difference. Stand up slowly, especially first thing in the morning. Eat smaller, more frequent meals to reduce postprandial drops. Avoid prolonged standing in hot environments. If a medication seems to be the cause, your doctor can often adjust the dose or switch to an alternative.
Low Blood Pressure During Pregnancy
Blood pressure commonly dips during the first and second trimesters of pregnancy as the circulatory system expands rapidly to support the growing baby. This is normal and expected. During pregnancy, a reading of 120/80 mm Hg or lower is considered within the healthy range. Most pregnant women with lower-than-usual readings simply experience occasional dizziness, particularly when standing up quickly, and the pressure returns to normal after delivery. The greater concern during pregnancy is actually blood pressure going too high, which can signal conditions like preeclampsia.