What is the most common cause of orthostatic hypotension?

Orthostatic hypotension, also called postural hypotension, is a fall in blood pressure after moving upright. Normally, blood vessels tighten and the heart adjusts quickly. Fluid loss from vomiting, diarrhoea, fever, heavy sweating or not drinking enough can reduce the blood available for that adjustment. Blood-pressure medicines, diuretics, anaemia, nerve disorders and heart problems may also contribute. Dizziness, blurred vision, weakness or feeling faint can happen after standing, but these symptoms have other possible causes too.

Rise slowly, sit on the edge of the bed before standing, and hold a stable surface. If symptoms start, sit or lie down promptly. Drink fluids unless a clinician has told you to restrict them. Review medicines with a clinician rather than stopping them yourself, particularly if episodes began after a dose change. A GP consultation can include lying and standing blood-pressure checks and a review for fluid loss or other illness.

Seek urgent help after fainting with injury, chest pain, severe breathlessness, confusion, new weakness, or a fast or irregular heartbeat. Prompt assessment is needed for repeated near-fainting, black stools, heavy bleeding, persistent vomiting or inability to keep fluids down.

Ask whether dehydration or a medicine may be contributing, how to check your blood pressure safely, whether blood tests are needed, and which fluid advice fits your heart and kidney health.