Lightheadedness: causes, red flags and when to seek help

The NHS uses dizziness as a broad term covering feeling off-balance, giddy, lightheaded or faint, or like you or your surroundings are spinning (vertigo). Sorting out which sensation you have is the first step, because the usual explanations differ.

Lightheadedness, the focus of this page, feels like a head-rush or a greying-out, often with tunnel vision, a hollow stomach or a need to hold on to something. It points to a temporary shortfall of blood or sugar reaching the brain. True spinning, particularly if it comes with hearing changes, suggests an inner-ear cause and is covered in the vertigo guide.

The NHS lists several everyday conditions that can bring on dizziness while you are ill with something else, including an ear infection, migraine, dehydration or heat exhaustion, stress or anxiety, low blood sugar because of diabetes, iron deficiency anaemia and motion sickness. For dizziness without an obvious reason it names a sudden fall in blood pressure when standing, inner-ear problems, labyrinthitis and the side effects of a new prescription medicine.

The NHS says low blood pressure is a reading of less than 90/60mmHg, that it does not always cause symptoms, and that if symptoms arise when you stand up or suddenly change position you may have postural hypotension. It notes that blood pressure varies with the time of day and what you are doing, that it can be low simply because you are fit and healthy or inherited it, and that pregnancy, some conditions such as diabetes and some medicines can cause it.

For symptom control the NHS suggests getting up slowly, taking care moving from lying to sitting to standing, eating small frequent meals and drinking more water, and avoiding long periods of standing, sudden changes of posture and too much alcohol. If a cause is found a GP may change a medicine or dose or suggest support stockings.

The NHS advises seeing a GP if dizziness will not go away or keeps coming back, if you are finding it harder to hear or speak, if there is ringing or other sounds in your ears, if you have double vision, blurred vision or other eyesight changes, if your face, arms or legs feel numb or weak, or if you have changes to your pulse, fainting or collapsing, headaches, or feeling or being sick.

Sudden weakness of the face or an arm, slurred speech or loss of vision with lightheadedness should be treated as a possible stroke and needs 999 straight away. Lightheadedness with crushing chest pain, severe breathlessness, a very fast or very slow pulse, or a blackout during exertion also calls for emergency care, as does faintness after a head injury or with black or bloody stools suggesting internal bleeding.

Fainting that happens without warning, while sitting or lying, or in someone with a family history of sudden cardiac death, deserves a same-day medical assessment with a heart tracing.

Expect questions about the exact sensation, how long it lasts, what you were doing, whether you have fainted, any palpitations or chest discomfort, recent illness, fluid and food intake, alcohol, and every medicine you take including over-the-counter and herbal products.

Examination centres on lying and standing blood pressure and pulse, taken a few minutes apart, to look for a significant drop on standing. The doctor will listen to the heart and lungs, look for pallor, check blood sugar with a finger prick and may test eye movements and balance.

The NHS says you can have your blood pressure checked by a pharmacist, practice nurse or GP, or at home with a monitor. A resting ECG is the usual next step if the heart rhythm is in question. Blood tests commonly include a full blood count for anaemia, kidney function and electrolytes, glucose and sometimes thyroid function and ferritin.

• Lying and standing blood pressure.

• Electrocardiogram, with 24-hour or longer monitoring if episodes are intermittent.

• Echocardiogram if a structural heart problem is suspected.

• Tilt-table testing in selected people with unexplained fainting.

• Blood tests for anaemia, glucose, kidney function and thyroid.

The NHS says to lie down until the dizziness passes and then get up slowly, move slowly and carefully, rest, drink plenty of fluids especially water, and avoid coffee, cigarettes, alcohol and drugs. It warns against bending down or getting up suddenly.

If you faint or nearly faint, lying down with the legs raised helps blood return to the brain. Planning regular meals, staying hydrated in hot weather and pausing at the edge of the bed before standing in the morning are all low-effort habits that reduce episodes.