Why does low blood pressure cause dizziness?

Blood pressure helps move blood to the brain when you change position. If pressure drops or the body does not adjust quickly enough after sitting or lying down, you may feel lightheaded, unsteady, weak or close to fainting. Dizziness is a very common presentation of Low Blood Pressure. Dizziness can also arise from inner-ear problems, medicines, low blood sugar and other causes, so it needs assessment when it is new or recurring.

When dizziness starts, sit or lie down promptly to reduce the chance of a fall. Rise slowly from bed or a chair, holding on to something stable. Drink fluids if you are able to drink normally and have not been told to limit fluids. Avoid driving, climbing or operating equipment while dizzy. Record when it happens, your position, recent illness, meals, fluid intake and medicines, then take that information to a clinician.

Arrange a prompt medical review for repeated episodes, fainting, falls, new palpitations, vomiting or diarrhoea, or dizziness after starting or changing a medicine. Seek emergency help for chest pain, severe shortness of breath, new weakness or numbness, trouble speaking, a severe sudden headache, black or bloody stools, or collapse. These symptoms may signal a cause needing immediate treatment.

Ask whether your blood pressure should be measured lying and standing, whether a medicine or fluid loss could be involved, and what steps are appropriate for your health conditions.