Orthostatic intolerance
The umbrella label for symptoms — lightheadedness, palpitations, pre-syncope, brain fog — that come on with upright posture and improve when you lie down. POTS and orthostatic hypotension are specific patterns within it.
Reviewed 2026-05-15
The umbrella, and what sits under it
Orthostatic intolerance (OI) is the symptom pattern, not the diagnosis. Specific diagnoses that sit under OI include:
- POTS — a heart-rate criterion (≥30 bpm rise in adults, ≥40 bpm in adolescents) within 10 minutes of standing.
- Orthostatic hypotension — a blood-pressure criterion (≥20 mmHg systolic or ≥10 mmHg diastolic drop within 3 minutes).
- Neurally mediated syncope — a pattern of triggered fainting episodes, often after prolonged standing.
Why the distinction matters
The treatment and follow-up plan depends on which specific pattern your specialist identifies. Two patients with similar symptoms can have very different physiology — one driven by impaired venous return, another by excess sympathetic activity (hyperadrenergic POTS). The numbers from a standing test usually distinguish them.