Blood pressure is generally considered low when it drops below 90/60 mmHg. That first number (systolic) measures the pressure when your heart beats, and the second (diastolic) measures pressure between beats. But the number alone doesn’t always tell the full story. Some people walk around at 85/55 their entire lives and feel perfectly fine. Low blood pressure only becomes a medical concern when it causes symptoms or drops suddenly enough to signal an underlying problem.
A drop of just 20 mmHg from your usual reading can be enough to make you dizzy or faint. So if you normally sit at 120/80 and your pressure falls to 100/60, you might feel it even though that reading looks “normal” on paper. What matters most is the combination of your numbers and how you feel.
Common Symptoms of Low Blood Pressure
When blood pressure drops low enough to reduce blood flow to your brain and organs, you’ll typically notice it. The most common signs include dizziness or lightheadedness, blurred or fading vision, fatigue, difficulty concentrating, nausea, and fainting. These symptoms often come on when you stand up, exercise, or haven’t eaten or hydrated enough.
Severely low blood pressure can lead to shock, which is a medical emergency. Signs of shock look different from everyday lightheadedness: cold, clammy skin, pale complexion, rapid and shallow breathing, a weak and fast pulse, and confusion (especially in older adults). Shock means your organs aren’t getting enough blood to function, and it requires immediate medical attention.
Types of Low Blood Pressure
Not all low blood pressure works the same way. The type depends on when and why it happens.
Orthostatic hypotension is the most common form. It happens when your blood pressure drops after standing up, defined as a fall of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of getting to your feet. It tends to be worst first thing in the morning because your body loses fluid overnight. Heat, alcohol, dehydration, prolonged bed rest, and certain medications all make it worse.
Postprandial hypotension is a blood pressure drop that occurs within two hours of eating, particularly after large meals high in carbohydrates or paired with alcohol. Digestion redirects blood flow to your gut, and in some people the body doesn’t compensate quickly enough to maintain pressure elsewhere. This is more common in older adults.
Neurally mediated hypotension happens when the communication between your brain and heart misfires. Standing for long periods is a classic trigger. Your brain incorrectly signals your heart to slow down, blood pressure drops, and you feel faint or actually pass out. This type is more common in younger people and children.
What Causes Low Blood Pressure
Plenty of everyday and medical factors can push blood pressure down. Dehydration is one of the most common culprits, whether from not drinking enough water, sweating heavily, vomiting, or diarrhea. When your blood volume drops, pressure naturally follows.
Heart conditions that reduce the heart’s pumping ability, including heart valve problems, heart failure, and very slow heart rates, can lower blood pressure. Endocrine disorders like thyroid problems, adrenal insufficiency, and low blood sugar also play a role because hormones help regulate how tightly your blood vessels constrict and how much fluid your kidneys retain.
Several categories of medication are known to lower blood pressure as a side effect. Diuretics (water pills), blood pressure medications themselves when dosed too aggressively, certain antidepressants, drugs for Parkinson’s disease, and erectile dysfunction medications can all contribute. If you started a new medication and began feeling lightheaded, the timing is worth mentioning to your doctor.
Severe infections, allergic reactions, and significant blood loss can cause dangerous, sudden drops in blood pressure. These are acute emergencies rather than the chronic low readings most people are searching about.
Low Blood Pressure During Pregnancy
Blood pressure naturally decreases during pregnancy. It steadily drops through the first and second trimesters, reaching its lowest point around mid-pregnancy, then gradually climbs back up toward delivery. By the end of pregnancy, readings typically return close to where they started in the first trimester. This dip is caused by hormonal changes that relax blood vessel walls and by the demands of increased blood flow to the placenta. Mild dizziness during pregnancy is common and usually not dangerous, but sudden or severe drops deserve attention.
How Low Blood Pressure Is Diagnosed
Diagnosis starts with a simple blood pressure reading, but if your doctor suspects a specific type of hypotension, they may go further. One common test is the tilt table test: you lie flat on a padded table, strapped in securely, and the table tilts you to a nearly upright position (about 70 degrees) within 10 seconds. You stay upright for up to 45 minutes while monitors track your blood pressure, heart rate, and heart rhythm. The test reveals how your nervous system responds to the shift in position and can help pinpoint orthostatic or neurally mediated hypotension.
Blood tests may be used to check for anemia, blood sugar issues, or hormonal imbalances. In some cases, an electrocardiogram or echocardiogram helps rule out heart-related causes.
Managing Low Blood Pressure
If your low blood pressure isn’t causing symptoms, it usually doesn’t need treatment. In fact, running on the lower end is associated with lower cardiovascular risk over time. Treatment is really about relieving symptoms and preventing falls or fainting episodes.
Increasing salt and fluid intake is one of the first strategies. For people with orthostatic hypotension, medical guidelines suggest sodium intake between 2,400 and 4,000 mg per day, and some specialists recommend even higher amounts (up to 4,800 mg) for conditions like postural tachycardia syndrome. That’s notably more than the 2,300 mg limit recommended for the general population, so this approach is specifically for people with diagnosed low blood pressure, not a general health tip.
Other practical strategies that help:
- Stand up slowly. Give your body 10 to 15 seconds to adjust before walking, especially in the morning.
- Eat smaller, more frequent meals. This reduces the blood flow diversion that causes postprandial drops.
- Stay hydrated. Drink water consistently throughout the day, and increase intake in hot weather or during exercise.
- Wear compression stockings. These reduce blood pooling in your legs and can raise overall blood pressure slightly.
- Limit alcohol. It dilates blood vessels and worsens most forms of hypotension.
- Avoid prolonged standing. If you must stand for long periods, shift your weight, cross your legs, or tense your calf muscles periodically.
When lifestyle changes aren’t enough, medications that either increase blood volume or tighten blood vessels can be prescribed. The choice depends on the type and severity of your hypotension, and your doctor will typically start with the lowest effective approach before adding medication.