# Orthostatic Hypotension > Orthostatic hypotension for NEET-PG Medicine covering its definition, neurogenic and non-neurogenic causes, and fludrocortisone and midodrine use. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/orthostatic-hypotension - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Harrison's Principles of Internal Medicine; Consensus statement on the definition of orthostatic hypotension; Davidson's Principles and Practice of Medicine - How to cite: "Orthostatic Hypotension", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/orthostatic-hypotension ## Direct answer Orthostatic hypotension is a sustained fall in systolic blood pressure of at least 20 mmHg, or diastolic pressure of at least 10 mmHg, within three minutes of standing or head-up tilt. It is divided into neurogenic causes, where autonomic failure blunts the compensatory heart rate rise, and non-neurogenic causes such as volume depletion and drugs, where tachycardia is preserved. Management starts with fluids, salt and a review of medicines, and drugs such as fludrocortisone or midodrine are added when these fail. ## What you must remember - **Consensus definition:** a systolic fall of 20 mmHg or more, or a diastolic fall of 10 mmHg or more, within three minutes of standing. - **Neurogenic causes:** pure autonomic failure, multiple system atrophy, Parkinson disease with autonomic involvement, Lewy body disease, diabetic autonomic neuropathy, amyloidosis and spinal cord lesions. - **Non-neurogenic causes:** volume depletion from haemorrhage, diarrhoea or diuretics, adrenal insufficiency, anaemia, prolonged bed rest, and drugs such as alpha-blockers, nitrates, tricyclics and antihypertensives. - **Diagnostic clue:** a blunted heart rate response favours neurogenic failure, whereas tachycardia on standing favours volume depletion or drug effect. - **Non-drug measures:** fluid intake of two to two and a half litres daily, added salt, raising the head of the bed, abdominal binders and compression stockings, and avoiding large meals and heat. - **Drug therapy:** fludrocortisone expands plasma volume; midodrine, an alpha-1 agonist, is timed in the morning and afternoon to avoid supine hypertension; droxidopa is a norepinephrine precursor used where licensed. ## A 70-year-old with Parkinson disease who falls on standing A 70-year-old man with Parkinson disease has recurrent dizziness and a fall when he stands from his chair after breakfast. Lying and standing blood pressures show a fall of 30 mmHg systolic within three minutes, with only a small rise in heart rate, which points to neurogenic failure. 1. **Review the medicines:** A drug review removes any alpha-blocker or vasodilator. 2. **Advise fluids and salt:** The patient is advised to increase fluid and salt intake and to sit before standing. 3. **Start midodrine if needed:** When these measures are insufficient, midodrine is started at a low dose and given in the morning and afternoon, with the last dose about four hours before bedtime to limit night-time supine hypertension. 4. **Consider fludrocortisone:** Fludrocortisone expands plasma volume, but it can cause supine hypertension and hypokalaemia, so potassium and blood pressure are monitored. 5. **Check supine pressure first:** Supine blood pressure is checked before increasing either drug, because treating standing hypotension at the cost of severe supine hypertension is the classic failure in this group. ## Where the examiner separates the look-alikes Orthostatic hypotension is most often confused with other causes of dizziness on standing. - **Trap:** Labelling every faint on standing as vasovagal syncope. — **Correct:** Vasovagal syncope typically follows prolonged standing or emotional stress and is not defined by a fall within three minutes. - **Trap:** Diagnosing orthostatic hypotension from a rapid pulse alone. — **Correct:** Postural tachycardia syndrome is a sustained rise in heart rate of 30 beats per minute or more within ten minutes of standing, without a fall in blood pressure, which is a distinct entity. - **Trap:** Treating a fall after a meal as the same condition. — **Correct:** Post-prandial hypotension is separate and is managed with smaller meals and by avoiding large carbohydrate loads. - **Trap:** Missing autonomic failure in parkinsonism. — **Correct:** The older name Shy-Drager syndrome, now usually called multiple system atrophy with autonomic failure, links autonomic failure with parkinsonism and is worth memorising. ## Frequently asked questions ### What defines orthostatic hypotension? Orthostatic hypotension is defined as a sustained fall in systolic pressure of at least 20 mmHg or diastolic pressure of at least 10 mmHg within three minutes of standing. The standing reading is compared with the supine value taken before standing. ### How does neurogenic orthostatic hypotension differ from the non-neurogenic type? Neurogenic orthostatic hypotension results from autonomic failure, so the heart rate fails to rise appropriately on standing. Non-neurogenic causes such as volume depletion or drugs preserve the compensatory tachycardia. ### Why is midodrine given in the morning and afternoon only? Midodrine causes supine hypertension when taken late in the day, so doses are timed in the morning and afternoon. The last dose is usually taken about four hours before bedtime to limit night-time blood pressure elevation. ### What is postural tachycardia syndrome? Postural tachycardia syndrome is a sustained rise in heart rate of at least 30 beats per minute within ten minutes of standing, without a fall in blood pressure. It is a distinct entity from orthostatic hypotension and is often confused with it in examination questions.