When you stand up, gravity immediately pulls about 500 to 800 milliliters of blood downward into your legs and abdomen. This reduces the amount of blood flowing back to your heart, which temporarily lowers your blood pressure. Normally, your body corrects this within seconds. When that correction fails or falls short, you feel dizzy, lightheaded, or even faint. The medical term for this is orthostatic hypotension, and it’s formally defined as a drop of at least 20 mmHg in systolic blood pressure (the top number) or 10 mmHg in diastolic pressure within three minutes of standing.
This is remarkably common. About one in five adults over 65 experiences it regularly, and nearly one in four older adults in long-term care settings does. But it’s not limited to older people. Dehydration, medications, and several medical conditions can cause it at any age.
How Your Body Normally Corrects the Drop
Your cardiovascular system has a built-in correction mechanism called the baroreceptor reflex. Specialized pressure-sensing cells sit in the walls of your major arteries near your heart and neck. When blood pressure falls, these cells detect less stretch on the artery walls and immediately reduce the signals they send to your brain. Your brain interprets this as “blood pressure is too low” and responds in two ways: it speeds up your heart rate so more blood gets pumped per minute, and it tightens your blood vessels to push blood pressure back up. The whole process takes just a few heartbeats.
When this system works properly, you never notice the brief dip. The problem starts when something interferes with any step in the chain, whether it’s the sensors themselves, the nerve signals, the heart’s ability to speed up, or the blood vessels’ ability to constrict.
The Most Common Causes
Dehydration and Low Blood Volume
The simplest and most frequent trigger is not having enough fluid in your system. When you’re dehydrated, your total blood volume drops, which means there’s less blood available to circulate when gravity pulls it downward. Fever, vomiting, diarrhea, heavy sweating during exercise, and simply not drinking enough water can all reduce blood volume enough to cause dizziness on standing. Low blood sugar and overheating can produce similar symptoms even without significant dehydration.
Medications
Drugs are one of the leading causes of blood pressure drops on standing, especially in older adults. The biggest culprits include:
- Diuretics (water pills): These increase urine output and reduce blood volume. Loop diuretics also expand vein capacity, meaning more blood pools in your lower body. Studies show loop diuretics carry up to a tenfold increased risk of orthostatic hypotension.
- Alpha-blockers: Often prescribed for prostate problems or high blood pressure, these block the receptors your blood vessels need to constrict. Without that tightening response, blood pressure can’t recover when you stand.
- Antidepressants: Tricyclic antidepressants cause orthostatic drops in 10 to 50 percent of people taking them. SSRIs roughly double the risk. SNRIs can also interfere with the nerve signals that regulate blood vessel tone.
- Antipsychotics: Up to 40 percent of people on antipsychotic medications develop orthostatic hypotension, primarily because these drugs block the same receptors alpha-blockers do.
- Benzodiazepines: These relax muscles throughout the body, including the muscles surrounding veins. That relaxation increases the amount of blood that pools in your legs when you stand.
- Nitrates: Used for chest pain, nitrates widen veins and reduce the blood returning to your heart.
If you take any of these medications and notice dizziness on standing, that connection is worth raising with whoever prescribed them. Sometimes adjusting the dose or timing resolves the problem.
Nervous System Conditions
A more serious category involves damage to the nerves that control blood vessel constriction. This is called neurogenic orthostatic hypotension, and it occurs in several neurodegenerative conditions. About 30 percent of people with Parkinson’s disease develop it. In multiple system atrophy, a rarer condition, the prevalence reaches 78 percent. Roughly half of people with dementia with Lewy bodies experience it as well. In these diseases, the protein deposits that damage the brain also damage the autonomic nerves responsible for tightening blood vessels and adjusting heart rate, so the body simply can’t mount the reflex it needs.
What It Feels Like
The hallmark symptom is lightheadedness or dizziness within seconds to minutes of standing. But the experience can go well beyond that. Some people notice blurred or tunneling vision as blood flow to the brain dips. Others feel sudden weakness in the legs, mental confusion, or a foggy sensation that makes it hard to think clearly. In more severe cases, the blood pressure drop is large or prolonged enough to cause fainting.
The timing matters. Some people feel it instantly, within the first 15 to 30 seconds of standing, which is called initial orthostatic hypotension. The “classical” form shows up between 30 seconds and 3 minutes. A delayed form develops gradually after 3 or more minutes of standing, which is why some people feel fine at first but get progressively worse while waiting in line or standing in the shower.
When It’s Harmless vs. Worth Investigating
Occasional lightheadedness after standing up quickly on a hot day, after a long bath, or when you haven’t had enough water is usually nothing to worry about. It reflects mild, temporary volume depletion, and it resolves on its own once you rehydrate or cool down. Sitting for a long time and then standing abruptly can produce the same brief wooziness.
The picture changes when it happens repeatedly, when you actually faint, or when it’s accompanied by confusion or persistent weakness. Frequent episodes increase your risk of falls and injuries, particularly for older adults. Recurrent orthostatic hypotension has also been linked in research to a higher long-term risk of cardiovascular problems. If you’re experiencing this regularly, or if it started after beginning a new medication, getting your blood pressure measured in both lying and standing positions is a straightforward first step in figuring out what’s going on.
Practical Ways to Reduce Symptoms
Fluid and Salt Intake
Increasing your blood volume is the most direct fix. Aim for about 1.25 to 2.5 liters of water or other fluids spread across the day, roughly five to eight glasses. Salt helps your body retain that fluid: a target of 10 to 20 grams of salt per day is often recommended for people with confirmed orthostatic hypotension, though this is significantly more than most dietary guidelines suggest for people with normal blood pressure. Salty broths and soups are an easy way to increase intake without relying on salt tablets.
Physical Counter-Pressure Maneuvers
Simple muscle contractions can squeeze blood out of your leg veins and push it back toward your heart, buying your body time to adjust. Effective techniques include crossing your legs and squeezing your thighs together, tensing your calf and thigh muscles while standing, squatting (even briefly), and clenching your fists or tensing your arms. One study-backed approach is the “crash position,” squatting down and tucking your head between your knees, which rapidly restores blood pressure if you feel faint.
Timing matters here too. Tensing your leg muscles before you stand is more effective than waiting until after you’re already upright. If you know standing tends to make you dizzy, contracting your calves and thighs for a few seconds while still seated can preload your circulation and blunt the initial drop.
Everyday Habits
Stand up in stages. Sit at the edge of the bed for 30 seconds before getting to your feet, especially first thing in the morning when blood pressure is naturally at its lowest. Avoid standing motionless for long periods. If you have to stand in place, shift your weight, rise onto your toes, and keep your leg muscles engaged. Compression stockings that reach the waist can also reduce the amount of blood that pools in your legs, though thigh-high or knee-high versions are less effective because so much pooling happens in the abdomen.
Alcohol and large meals both worsen the problem. Alcohol dilates blood vessels, and digesting a big meal diverts blood to your gut. Eating smaller, more frequent meals and limiting alcohol, particularly before situations where you’ll need to stand, can make a noticeable difference.