Orthostatic refers to anything related to standing upright, and in medical contexts, it almost always describes a drop in blood pressure that happens when you go from sitting or lying down to standing. The full term is orthostatic hypotension, and it’s diagnosed when your systolic blood pressure falls by at least 20 mmHg or your diastolic pressure drops by 10 mmHg within three minutes of standing up. That blood pressure drop can make you feel dizzy, lightheaded, or even cause you to faint.
What Happens in Your Body When You Stand
When you’re lying flat, gravity isn’t pulling blood away from your brain. The moment you stand, roughly 500 to 700 milliliters of blood shifts downward into your legs and abdomen. Your body has a rapid correction system for this. Pressure sensors in your neck and chest detect the drop and send signals to your brainstem, which responds in two ways: it speeds up your heart rate and tightens your blood vessels. In a healthy person, this correction happens so fast that blood pressure stays essentially the same whether you’re lying down or standing up.
Orthostatic hypotension occurs when any part of that correction system fails. The pressure sensors might not detect the change properly. The nerves carrying the signal might be damaged. The blood vessels might not tighten enough. Or there simply might not be enough blood volume to maintain adequate pressure. The result is the same: not enough blood reaches your brain, and you feel it immediately.
What It Feels Like
The most common symptom is lightheadedness within seconds of standing, sometimes described as a head rush or feeling like the room is tilting. Many people also experience visual disturbances, things going dark or spotty around the edges. Other symptoms include fatigue, difficulty concentrating, nausea, sweating, weakness, and headache. In more severe cases, you can lose consciousness entirely, which is the main injury risk since falls from fainting can cause serious harm.
These symptoms reliably improve when you sit or lie back down, which is one of the distinguishing features of orthostatic problems. If your dizziness doesn’t change with position, something else is likely going on.
Common Causes
Medications are one of the most frequent triggers. Several drug classes can interfere with your body’s blood pressure correction when standing. The highest-risk categories include blood pressure medications that relax blood vessels, water pills that reduce fluid volume, and many psychiatric medications including antipsychotics, older antidepressants, anti-anxiety medications, and sleep aids. Opioid pain medications and Parkinson’s medications also carry significant risk. Even newer antidepressants (SSRIs and SNRIs) can contribute, though at lower rates.
Dehydration is another straightforward cause. If your blood volume is low from not drinking enough, sweating heavily, vomiting, or diarrhea, there’s simply less fluid to push upward against gravity. Prolonged bed rest or standing still for long periods can also weaken the body’s reflexes and allow blood to pool excessively in the legs.
Neurogenic Orthostatic Hypotension
A more serious form occurs when the nerves controlling blood vessel tightening are damaged or degenerating. This is called neurogenic orthostatic hypotension, and it shows up in about 30% of people with Parkinson’s disease. The same nerve damage occurs in other neurodegenerative conditions, including multiple system atrophy and dementia with Lewy bodies. Diabetes and other conditions that damage peripheral nerves can also cause it. In these cases, the body physically cannot release the chemical signals needed to tighten blood vessels when you stand, so the blood pressure drop is more severe and harder to manage.
How It Differs From POTS
Postural orthostatic tachycardia syndrome (POTS) is a related but distinct condition. In orthostatic hypotension, the main problem is a blood pressure drop. In POTS, blood pressure typically stays stable in the first three minutes of standing, but heart rate jumps by at least 30 beats per minute in adults (40 in adolescents). POTS is actually only diagnosed after orthostatic hypotension has been ruled out. Both conditions cause lightheadedness and difficulty standing, but the underlying mechanism is different, and so is the treatment approach.
How It’s Measured
Testing is straightforward. You lie down for five minutes while your blood pressure and heart rate are recorded. Then you stand, and measurements are repeated at one minute and again at three minutes. If your systolic pressure drops by 20 mmHg or more, or your diastolic drops by 10 mmHg or more, within that three-minute window, you meet the diagnostic criteria. Some clinics use a tilt table, which gradually raises you to a 60-degree angle, to get the same information in a more controlled way. Your doctor will also note whether your heart rate increases appropriately, which helps distinguish between neurogenic and non-neurogenic causes.
Managing Orthostatic Symptoms
The first-line approach is almost always lifestyle changes rather than medication. Fluid intake should be at least 2 liters per day, with some guidelines recommending up to 2.5 liters. Increasing salt intake to 5 to 10 grams daily helps your body retain that fluid and maintain blood volume. This is the opposite of the usual dietary advice for blood pressure, which is why it’s important to know whether your blood pressure problem is too high, too low, or both at different times of day.
Compression garments, particularly waist-high compression stockings or abdominal binders, help prevent blood from pooling in your legs and belly when you stand. They’re not the most comfortable solution, but they can make a real difference for people with moderate to severe symptoms. Regular exercise, especially endurance training and core strengthening, also improves the body’s ability to regulate blood pressure with position changes over time.
Physical Tricks That Help in the Moment
If you feel symptoms coming on, several physical maneuvers can temporarily raise your blood pressure enough to prevent fainting. Crossing your legs while tensing your thigh and buttock muscles is one of the most effective, shown in studies to meaningfully increase blood pressure in people with orthostatic hypotension. Squatting works even better if you’re able to do it safely. Tensing your arm muscles (making fists and flexing) raises pressure quickly. Even smaller movements like fidgeting your legs, doing calf raises, or marching in place can help by activating the muscle pump that pushes blood back up toward your heart.
These aren’t cures, but they buy you time. If you feel a wave of lightheadedness, crossing your legs and squeezing, or simply squatting down, can be the difference between riding it out and hitting the floor.