Supine Hypotension Causes: What to Know

Blood pressure depends on circulating fluid, the pumping action of the heart, blood-vessel tightening, and signals from the nervous system. Vomiting, diarrhoea, fever, sweating, or bleeding can reduce fluid in the circulation. Medicines for blood pressure, the heart, sleep, mood, or pain may lower pressure or affect the body’s response to posture. Heart rhythm or pumping problems, hormone disorders, anaemia, and nerve conditions can also be relevant. A clinician will consider your timing, other symptoms, medical history, and medicines rather than relying on one reading.

Write down when symptoms occur, whether you were lying, sitting, or standing, what you had eaten or drunk, and any recent illness or medicine change. Bring all medicines and supplements to a [GP Consultation](/treatments/consultations-and-assessment/gp-consultation/). Assessment may include repeated blood-pressure checks, a pulse check, and targeted tests based on your history. Do not stop prescribed medicine or take extra salt or fluids unless a clinician advises it for your circumstances.

Seek emergency help for fainting with injury, chest pain, severe breathlessness, severe confusion, new weakness, or difficulty speaking. Arrange prompt review after heavy vomiting, diarrhoea, suspected bleeding, or a sudden change after starting or changing medicine. Recurring light-headedness, falls, or reduced ability to stand safely also warrants medical assessment. For background on a common related symptom, see [Dizziness](/symptoms/dizziness/).

Which causes fit the timing of my symptoms? Could any medicine or supplement be contributing? Do I need blood tests, heart checks, or posture-related readings? What fluid advice is safe with my other health conditions?