The short answer: in most cases your blood pressure drops too far, too fast, when you stand. That is called orthostatic hypotension, defined as a fall of 20 mm Hg or more systolic, or 10 mm Hg or more diastolic, within three minutes of standing. It affects about 5% of middle-aged adults and roughly 20% of adults over 60. Dehydration and medications explain a large share of cases, and both are fixable. A smaller group has a nerve-signaling problem or a different condition entirely, such as POTS or an inner-ear disorder.

The useful question is not "am I dizzy?" It is "what are the numbers doing?" Two minutes with a blood pressure cuff separates most of these causes.

What is actually happening when you stand?

Standing up moves roughly half a liter to a liter of blood into the veins of your legs and abdomen. Less blood returns to the heart, so the heart has less to pump out, and blood pressure starts to fall. Within seconds, pressure sensors in your neck and chest detect that fall and signal the nervous system to tighten blood vessels and speed the heart.

When that reflex works, you feel nothing. When it is slow, blunted, or fighting against low blood volume, pressure in the brain drops briefly and you get the familiar grey-out: lightheadedness, tunnel vision, muffled hearing, a few seconds of unsteadiness. It usually clears within 10 to 30 seconds because the reflex catches up.

That description matters because it separates orthostatic dizziness from spinning vertigo. Orthostatic dizziness is a fading or floating sensation triggered by the act of standing. Vertigo is a false sense of motion, and it does not care whether you are upright.

How is it measured?

A 2022 review in American Family Physician describes the standard bedside test: measure blood pressure and heart rate after lying down for five minutes, then measure again after three minutes of standing (Ringer & Lappin, AFP 2022).

Orthostatic hypotension is diagnosed when the systolic reading falls by at least 20 mm Hg, or the diastolic reading falls by at least 10 mm Hg. In people who already have high blood pressure while lying down, a systolic drop of 30 mm Hg or more is used instead.

The heart rate matters as much as the pressure. The review describes a ratio of the heart rate rise to the systolic pressure fall. A ratio below 0.5 beats per mm Hg points to a neurogenic cause, meaning the autonomic nerves are not responding. A ratio of 0.5 or higher points to a non-neurogenic cause such as dehydration, blood loss, or a medication. Put plainly: if your pressure drops 30 points and your pulse barely moves, that is a different problem from a pressure drop with a pulse that jumps 20 beats.

You can run a version of this at home with an automatic cuff. Record both numbers and your pulse in each position, repeat on three separate mornings, and bring the log to your appointment. Our guide to symptom journaling covers how to record it usefully.

What causes it?

The AFP review sorts causes into two groups.

Non-neurogenic causes

These are the common and correctable ones: dehydration, blood loss, anemia, prolonged bed rest, heat exposure, alcohol, large meals, and heart conditions that limit output. Medications are the single most productive place to look. The named offenders include antihypertensives and diuretics, alpha-blockers prescribed for prostate symptoms, dopaminergic drugs for Parkinson disease, opioids, anticholinergics, and psychoactive medications. One retrospective study cited in the review found a 23% higher prevalence of orthostatic hypotension in older patients taking even one of these drug classes.

If you are on blood pressure treatment, this is worth raising specifically rather than assuming the dose is fixed. Our sister site hypertension.md covers how those medications are chosen and adjusted.

Neurogenic causes

Here the autonomic nervous system itself is impaired. The list includes Parkinson disease, multiple system atrophy, Lewy body dementia, pure autonomic failure, diabetic autonomic neuropathy, amyloidosis, and some autoimmune neuropathies. These cases tend to be more persistent, less responsive to fluids alone, and are the reason a first episode in an older adult deserves a proper evaluation rather than reassurance.

Is it POTS instead?

Postural orthostatic tachycardia syndrome is a different pattern. In POTS the blood pressure holds steady, but the heart rate climbs by at least 30 beats per minute within 10 minutes of standing, and the symptoms persist for three months or more. In adolescents the threshold is 40 beats per minute.

Symptoms overlap heavily with orthostatic hypotension: lightheadedness, palpitations, fatigue, brain fog, and exercise intolerance. The distinguishing feature is the racing pulse without a pressure drop. POTS is far more common in younger people and disproportionately affects women. It is often diagnosed after a viral illness, surgery, or a period of prolonged inactivity.

This is exactly why the home log should include pulse. Blood pressure alone cannot tell these two apart.

Could it be the inner ear instead?

Sometimes. Benign paroxysmal positional vertigo produces brief, intense spinning triggered by head position changes: rolling over in bed, tipping the head back, bending to pick something up. People often describe it as "dizzy when I get up," which sends the workup down the wrong path.

Two questions usually separate them. Does the room spin, or do you fade out? And does it happen when you roll over in bed while still lying flat? Spinning that occurs while horizontal is not a blood pressure problem. If the trigger is head position rather than the act of standing, the inner ear moves to the top of the list.

What actually helps?

The non-drug measures come first, and in mild cases they are often enough. The AFP review recommends:

  • 2 to 2.5 liters of fluid per day, spread through the day rather than in bursts.
  • At least 2 to 3 grams of sodium per day, which is a deliberate increase and must be cleared with a clinician if you have heart failure, kidney disease, or high blood pressure.
  • Waist-high compression garments at 30 to 40 mm Hg of graded pressure. Knee-high stockings do not reach the abdominal veins where most of the pooling happens.
  • Physical counter-maneuvers when symptoms begin: crossing the legs and squeezing, squatting, or tensing the thigh and buttock muscles.
  • Staged rising. Sit on the edge of the bed for 30 seconds, pump your ankles, then stand.

Two more habits help. Avoid alcohol in the evening, and be alert after large carbohydrate-heavy meals, which shunt blood to the gut and can drop pressure for an hour or two afterward.

When those measures fail, prescription options exist. The review lists midodrine, started at 2.5 mg three times daily and titrated up to 10 mg three times daily; droxidopa, from 100 mg to 600 mg three times daily; and fludrocortisone, 0.1 mg titrated to 0.2 mg daily, with a note about long-term risks. These are clinician decisions, and all three can raise blood pressure while lying down, which is its own problem.

When should you see a doctor?

Book an appointment if any of these apply:

  • You have actually fainted, or come close enough that you had to sit down to avoid it.
  • The episodes are frequent enough to change what you do during the day.
  • Your systolic pressure drops 30 mm Hg or more on standing.
  • The symptoms started or worsened within weeks of a new medication or a dose change.
  • You also have black or bloody stools, heavy periods, or unexplained fatigue, which raise the question of blood loss or anemia.

Seek urgent care for dizziness with chest pain, shortness of breath, an irregular or very fast heartbeat, a severe sudden headache, new weakness or numbness, trouble speaking, or double vision. Those combinations point away from simple pooling. Our guide to red flag symptoms covers how these features behave across other complaints, and when to see a doctor covers the general thresholds.

The bottom line

Dizziness on standing is usually a blood pressure timing problem, not a brain problem. Measure it: lying for five minutes, standing for three, with pulse recorded both times. A pressure drop of 20 systolic or 10 diastolic confirms orthostatic hypotension. A pulse jump of 30 or more with stable pressure points to POTS. Spinning while lying flat points to the inner ear.

Then work the two highest-yield causes first, because they explain most cases and cost nothing to test: fluid intake and the medication list. Bring both to the appointment along with your log.

Last updated: August 2026. This article is for informational purposes only and does not constitute medical advice. It cannot diagnose your symptoms. Do not stop or change a prescribed medication without speaking to the prescriber, and seek prompt care for dizziness with chest pain, fainting, or neurological symptoms.