Fainting and shaking when standing up: what to know

Fainting and shaking when standing up can occur when a sudden drop in blood pressure briefly reduces blood flow to the brain, but heart rhythm problems, dehydration, low blood sugar, anaemia, and seizures also need consideration. The shaking may be a brief series of jerky movements during a faint and does not by itself prove that a seizure occurred. A clinician may need to hear exactly what happened before, during, and after the episode.

Standing moves blood into the legs. Normally, the body tightens blood vessels and adjusts the heart rate to maintain circulation to the brain. If that response is too slow or insufficient, you may feel light-headed, see spots, become pale or sweaty, and collapse. This is often called orthostatic or postural hypotension. It can be encouraged by not drinking enough, vomiting, diarrhoea, heat, prolonged bed rest, or medicines that lower blood pressure.

Other explanations include dehydration, anaemia, hypoglycaemia, and an abnormal heart rhythm such as atrial fibrillation. A seizure can also cause loss of awareness and shaking, particularly when movements continue after the person is lying down or recovery is unusually confused. The position that triggered the event is useful information, but it cannot identify the cause on its own.

If you feel faint, sit or lie down immediately and raise your legs if comfortable. Move away from stairs, traffic, hot surfaces, and other hazards. Do not try to walk it off. If someone has fainted, place them on their back, check that they are breathing normally, loosen tight clothing, and keep the area clear. Do not give food or drink until they are fully alert.

After recovery, stand gradually: turn onto your side, sit for a while, then rise with support. Drink fluids if you can do so safely and have not been told to restrict them. Note what you were doing, how long warning symptoms lasted, whether shaking occurred, any injury, and how quickly you became oriented. Arrange a medical assessment if this is new, recurrent, or unexplained, and review medicines with a clinician rather than stopping them yourself.

Call emergency services if the person is not waking, is not breathing normally, has severe difficulty breathing, or has ongoing seizure-like movements. Seek urgent assessment for fainting with chest pain, a racing or irregular heartbeat, severe headache, new weakness, trouble speaking, significant injury, heavy bleeding, or pregnancy. An episode during exercise or while lying down also needs prompt medical review.

Arrange a timely appointment if faintness happens repeatedly on standing, lasts beyond a brief spell, follows a new medicine, or comes with persistent fatigue, thirst, vomiting, diarrhoea, or unusually heavy periods. Keep a record of episodes and ask someone who witnessed one to describe the movements and recovery.

Ask whether your blood pressure should be checked lying down and standing, whether an ECG or blood tests are appropriate, and whether any medicine or health condition could be contributing. Tell the clinician about skipped meals, fluid loss, alcohol, heat exposure, palpitations, family history of sudden cardiac death, and any tongue injury or prolonged confusion.