Dizziness when standing up: causes, red flags and when to get it checked

When you stand, around half a litre of blood moves to the legs. The nervous system normally tightens blood vessels and speeds the heart within seconds to compensate. If that response is slow or the blood volume is low, less blood reaches the brain, causing dizziness, grey vision or a feeling of fainting.

• Dehydration or low fluid intake, vomiting or diarrhoea, hot environments, and alcohol.

• Medicines: blood pressure tablets (especially alpha blockers, diuretics and combinations), tamsulosin and similar prostate drugs, some antidepressants, nitrates and Parkinson medicines.

• Standing quickly after lying down, or after prolonged rest or illness.

• Anaemia and low iron, which reduce oxygen delivery and can mimic or add to dizziness.

• Postural orthostatic tachycardia syndrome (POTS): racing heart, fatigue and dizziness on standing, mostly in younger people and often after viral illness.

• Autonomic nerve dysfunction from diabetes, Parkinson disease or other conditions.

• Heart rhythm problems or valve disease, adrenal insufficiency and, rarely, other hormone problems.

Dizziness on exertion rather than standing, chest pain, palpitations before collapse, collapse without warning, a family history of sudden cardiac death, or new neurological symptoms such as speech or vision loss point away from simple orthostatic hypotension.

• Call 999: collapse with chest pain, severe breathlessness, or a fit; fainting with new weakness, facial droop or slurred speech.

• Same-day GP or NHS 111: fainting with palpitations, injury from a fall, or black or bloody stools alongside dizziness.

• GP within days: repeated blackouts, falls, or dizziness after a new medicine.

• Routine GP: occasional light-headedness on standing that you would like looked at.

The doctor will want to know how soon after standing the symptoms start, how long they last, the circumstances of any blackouts, your fluid intake, alcohol, all medicines, and symptoms such as palpitations, chest pain or thirst. They will take blood pressure and pulse lying and after standing for one and three minutes, listen to the heart, and examine for anaemia and dehydration.

• Lying and standing blood pressure and pulse: the cornerstone test and cheap to do at the surgery.

• ECG: looks for rhythm problems or conduction disease.

• Blood tests: full blood count, kidney function, glucose, and sometimes thyroid or morning cortisol.

• Ambulatory ECG, echocardiogram or tilt-table testing: if cardiac causes or syncope remain unclear.

Stand up slowly, sit for a minute on the edge of the bed, and cross your legs or clench your calves before rising. Drink fluids steadily, with a salty drink if a doctor has said that is appropriate, and cut back alcohol. Compression stockings and raising the head of the bed can help some people. Do not stop prescribed medicines without advice; ask for a review instead.

On the NHS a GP reviews medicines and orders initial tests, with cardiology or a falls and syncope service if needed. Private cardiology or neurology consultations and tilt-table testing are available directly.