Low blood pressure is a reading below 90/60 mmHg. Unlike high blood pressure, which is almost always a concern, low blood pressure is only a problem when it causes symptoms or signals something else going on in your body. Some people naturally run low without any issues at all. The trouble starts when your blood pressure drops enough that your brain and organs aren’t getting the blood flow they need.
What the Numbers Mean
Blood pressure is measured with two numbers. The top number (systolic) reflects the force when your heart beats, and the bottom number (diastolic) reflects the pressure between beats. A reading of 120/80 is considered normal. When either number falls below 90/60, it’s classified as low blood pressure, or hypotension.
There’s no single number where low blood pressure becomes dangerous for everyone. A young, fit person might walk around at 85/55 and feel perfectly fine. What matters is whether the reading is low for you personally, and whether you’re experiencing symptoms. A sudden drop from your usual baseline is more concerning than a consistently low reading you’ve had for years.
Common Symptoms
When blood pressure is too low to deliver enough blood to your brain and other organs, you’ll typically notice it quickly. The most common signs include dizziness or lightheadedness, feeling faint or actually passing out, blurred vision, nausea, fatigue, and difficulty concentrating. These symptoms tend to be worse when you stand up quickly, especially first thing in the morning or after a meal.
In more severe cases, low blood pressure can cause cold, clammy, pale skin, rapid or shallow breathing, and a weak, fast pulse. These are signs that your body is struggling to compensate and may indicate shock, which is a medical emergency. Confusion or significant changes in mental state alongside very low readings warrant immediate attention.
What Causes It
Low blood pressure has a long list of possible causes, ranging from everyday and harmless to serious and treatable.
Dehydration is one of the most common triggers. When you lose more fluid than you take in, whether from heat, exercise, vomiting, or diarrhea, your blood volume drops and your pressure follows. Even mild dehydration can be enough to cause dizziness on standing.
Pregnancy frequently causes low blood pressure, especially during the first 24 weeks, because the circulatory system expands rapidly to supply the growing baby. This usually resolves after delivery.
Heart conditions like extremely slow heart rate, heart valve problems, and heart failure can all reduce the amount of blood your heart pumps out, leading to low pressure. Endocrine problems, including underactive thyroid and adrenal insufficiency, can also play a role by disrupting the hormones that help regulate blood pressure.
Medications are a frequent and often overlooked cause. Water pills (diuretics), beta-blockers, certain antidepressants, and drugs for erectile dysfunction can all lower blood pressure. If you started a new medication and began feeling dizzy or lightheaded, the timing is worth noting.
Blood loss from an injury or internal bleeding reduces blood volume quickly, and severe infections can cause a dramatic, dangerous drop in pressure as the body diverts resources to fight the infection.
Orthostatic Hypotension
One specific type worth knowing about is orthostatic hypotension, the kind that hits when you stand up. It’s defined as a drop of 20 mmHg or more in your systolic pressure, or 10 mmHg or more in your diastolic pressure, within a few minutes of standing. You might also feel lightheaded or dizzy even if the numbers don’t reach those exact thresholds.
This happens because gravity pulls blood toward your legs when you stand. Normally your body compensates almost instantly by tightening blood vessels and slightly increasing your heart rate. When that reflex is sluggish, whether from aging, medications, dehydration, or nervous system conditions, your brain briefly loses adequate blood flow. It’s more common in older adults and affects a significant number of people over 65.
A related condition involves your heart rate spiking dramatically when you stand (postural orthostatic tachycardia syndrome, or POTS), which can cause similar symptoms of dizziness and fainting even when the blood pressure drop itself is modest.
How It’s Diagnosed
Diagnosing low blood pressure starts simply: a blood pressure reading taken in different positions. Your provider will check your pressure while you’re lying down, then again shortly after you stand, watching for a significant drop.
If the cause isn’t obvious, further testing may include blood work to check for anemia, blood sugar problems, or thyroid dysfunction. An electrocardiogram can reveal heart rhythm or structural issues that might be reducing output.
For fainting episodes that are hard to pin down, a tilt table test can be helpful. You lie flat on a padded table while strapped in securely, and the table is quickly tilted to an upright position to mimic standing. Monitors track your blood pressure, heart rate, and heart rhythm throughout. If your body responds abnormally, showing a large blood pressure drop or a spike in heart rate, it helps pinpoint whether the problem is orthostatic hypotension, POTS, or a vasovagal response (where your nervous system overreacts to a trigger like stress or fatigue).
Practical Ways to Manage It
If your low blood pressure is mild and occasional, lifestyle changes are often enough to keep symptoms in check.
Increase your fluid intake. Dehydration is such a common contributor that simply drinking more water throughout the day resolves symptoms for many people. This is especially important in hot weather or when you’re exercising.
Add more salt to your diet. This is one of the rare situations where extra sodium is actually recommended. For people with low blood pressure, some physicians suggest at least 6 grams of salt daily, though the right amount depends on your overall health. Salt tablets are an option if you’d rather not rely on salty foods alone.
Eat smaller, more frequent meals. Large meals divert blood to your digestive system, which can worsen low pressure for an hour or two afterward. Splitting meals into smaller portions throughout the day helps keep things more stable.
Move slowly when changing positions. If orthostatic drops are your main issue, sit on the edge of the bed for a minute before standing. Flex your calves a few times. Avoid jumping up quickly from a lying or seated position.
Try compression stockings. The gentle pressure they apply to your lower legs prevents blood from pooling there when you stand. They typically raise blood pressure by about 5 to 10 mmHg, which can be enough to eliminate dizziness for people whose readings are borderline.
Limit alcohol. Even moderate drinking can lower blood pressure further and worsen dehydration.
Stay active. Regular exercise improves your body’s ability to regulate blood pressure, strengthens the cardiovascular system, and helps with the reflexes that keep blood flowing to your brain when you change positions. Just be cautious with exercises that involve rapid position changes until your symptoms are well managed.
When Low Blood Pressure Is Serious
Chronically low blood pressure without symptoms is generally not harmful. The concern arises when symptoms interfere with daily life, when readings drop suddenly from your normal baseline, or when low pressure is a sign of an underlying condition that needs treatment.
Severely low blood pressure that causes confusion, cold and clammy skin, rapid breathing, or a weak pulse suggests your organs may not be getting enough blood. This can result from significant blood loss, severe infection, a serious allergic reaction, or heart failure. These situations require emergency care, not home management.
If you’re regularly feeling dizzy, lightheaded, or faint, especially if it’s affecting your ability to work, drive, or move safely through your day, it’s worth getting checked. In many cases, the fix is straightforward: adjusting a medication, increasing fluids and salt, or treating an underlying condition you didn’t know about.