Low blood pressure, called hypotension, is any reading below 90/60 mmHg. For comparison, a normal blood pressure is around 120/80 mmHg. Many people naturally run on the lower side without any problems, but when blood pressure drops enough to reduce blood flow to the brain and organs, it causes symptoms that range from mild dizziness to fainting or, in rare cases, shock.
What the Numbers Mean
A blood pressure reading has two numbers. The top number (systolic) measures pressure when your heart beats. The bottom number (diastolic) measures pressure between beats. You’re considered to have low blood pressure when either number falls below the 90/60 threshold. That said, what’s “too low” varies from person to person. A reading of 85/55 in someone who feels perfectly fine isn’t a medical concern. Low blood pressure only becomes a problem when it causes symptoms or signals something else going on in the body.
Common Symptoms
The most recognizable sign of low blood pressure is lightheadedness or dizziness, especially when standing up. This happens because your brain temporarily isn’t getting enough blood. Other symptoms include blurred vision, nausea, fatigue, and difficulty concentrating. Some people notice cold or clammy skin, or feel generally “off” without being able to pinpoint why.
Fainting is the most dramatic symptom. It occurs when blood pressure drops sharply enough that the brain loses adequate blood flow for a few seconds. Most fainting episodes from low blood pressure resolve on their own once you’re lying down and blood flow returns to normal, but falls during fainting can cause serious injuries.
Why Blood Pressure Drops
Low blood pressure has a long list of possible causes, and identifying yours matters because the treatment depends entirely on what’s driving it.
Dehydration is one of the most common and easily fixable causes. When your body loses more fluid than it takes in, blood volume drops, and so does pressure. This can happen from not drinking enough water, heavy sweating, vomiting, or diarrhea.
Nutritional deficiencies play a role too. Low levels of vitamin B-12, folate, or iron can prevent your body from producing enough red blood cells, a condition called anemia. Fewer red blood cells means less oxygen-carrying capacity in the blood, which can lower blood pressure.
Medications are a frequent culprit. Blood pressure medications (including diuretics, alpha blockers, and beta blockers) can sometimes lower pressure too much. Certain antidepressants, Parkinson’s disease medications, and erectile dysfunction drugs can also cause drops, particularly erectile dysfunction medications taken alongside heart medications like nitroglycerin.
Heart conditions such as heart failure, heart valve problems, and an abnormally slow heart rate can reduce the heart’s ability to pump blood effectively. Hormone-related conditions like Addison’s disease, which affects the adrenal glands, can also cause blood pressure to fall. Diabetes and low blood sugar are additional contributors.
Pregnancy commonly causes lower blood pressure, particularly in the first 24 weeks, as the circulatory system expands rapidly. This is usually normal and resolves after delivery.
Types of Low Blood Pressure
Not all low blood pressure behaves the same way. The type you experience depends on when and why the drop occurs.
Orthostatic hypotension is the most common type. It happens when you stand up and your blood pressure drops by at least 20 points systolic or 10 points diastolic within three minutes. You feel it as a head rush or wobbly sensation right after getting out of bed or rising from a chair. It’s more common in older adults and people on blood pressure medications. Prolonged bed rest can also trigger it because the body loses its ability to adjust quickly to position changes.
Postprandial hypotension occurs after eating, when blood flow redirects to the digestive system. It primarily affects older adults and people with Parkinson’s disease or autonomic nervous system disorders.
Neurally mediated hypotension happens after standing for long periods. The brain and heart miscommunicate, causing a sudden drop in blood pressure and sometimes fainting. This type is especially common in younger people.
When Low Blood Pressure Becomes Dangerous
Chronically low blood pressure that causes no symptoms is not dangerous. The concern is when pressure drops suddenly or severely enough that organs aren’t getting adequate blood flow. The most serious form of this is shock, which is a medical emergency.
Signs of shock include confusion or agitation, rapid breathing, a fast but weak pulse, cold and clammy skin (sometimes with a bluish tint), and significantly reduced urination. Shock can result from severe blood loss, serious infections, or life-threatening allergic reactions (anaphylaxis). It requires immediate emergency care because organs begin to fail without adequate blood supply.
Even outside of shock, repeated fainting episodes from low blood pressure carry real risks. Falls can lead to broken bones, head injuries, or other trauma, particularly in older adults.
How Low Blood Pressure Is Diagnosed
A standard blood pressure cuff reading is the starting point. If your readings consistently fall below 90/60 and you’re experiencing symptoms, your doctor will look for the underlying cause. Blood tests can check for anemia, blood sugar problems, or hormone imbalances.
If you’re fainting and the reason isn’t clear, a tilt table test can help. During this test, you lie on a table that slowly tilts you from a flat position to a near-standing angle while your blood pressure and heart rate are monitored. If your blood pressure drops and you feel faint or actually pass out, that’s considered a positive result, pointing toward orthostatic hypotension or a related condition.
Managing Low Blood Pressure
If your low blood pressure isn’t causing symptoms, it typically doesn’t need treatment. For people who are symptomatic, the approach focuses on both addressing the root cause and making practical adjustments.
Drink more water. Increasing fluid intake raises blood volume, which directly supports blood pressure. This is especially important if dehydration is a factor or if you live in a hot climate.
Add salt to your diet. While most health advice centers on reducing sodium, people with low blood pressure may benefit from more of it. Salt helps retain fluid in the bloodstream, raising pressure. However, too much sodium can strain the heart over time, so this is a change worth discussing with a doctor rather than doing aggressively on your own.
Wear compression stockings. These elastic stockings, commonly associated with varicose veins, squeeze the legs gently to push blood back toward the heart. This reduces the amount of blood that pools in the lower body when you stand. Some people prefer compression belts worn around the abdomen, which work on a similar principle.
Change positions slowly. If orthostatic hypotension is your issue, take your time getting up. Sit on the edge of the bed for a minute before standing. Avoid crossing your legs while seated, and flex your feet a few times before rising to get blood moving.
If a medication is causing your low blood pressure, your doctor may adjust the dose or switch to a different drug. When an underlying condition like anemia, a thyroid disorder, or a heart problem is the cause, treating that condition usually resolves the blood pressure issue as well.