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What to do if…
you get an unexpectedly low blood pressure reading and feel weak or lightheaded

Produced and maintained by PanicStation.org Published: Last reviewed: Editorial policy UK guide

Short answer

Stop what you are doing, sit or lie down, and treat this as a fainting risk until you feel steady. If you feel you may pass out, lie down with your legs raised and ask someone to stay with you.

Do not do these things

  • Do not push through it, keep standing, or try to walk it off while you feel faint.
  • Do not drive, cycle, climb, use machinery, or get into a shower or bath while you feel lightheaded.
  • Do not take an extra dose of any blood pressure or heart medicine to try to fix the reading.
  • Do not keep standing up or moving around just to re-check the number.
  • Do not ignore chest pain, severe breathlessness, collapse, severe confusion, or new speech or movement problems.

What to do now

  1. Get into a safer position immediately.
    If you feel faint, lie on your back and raise your legs on a chair, cushion, or pillows. If you cannot lie down, sit down and lower your head, supported if possible.

  2. Get another person involved if you can.
    Tell someone nearby that you feel weak or lightheaded and ask them to stay with you for a few minutes. If you are alone, keep your phone within reach.

  3. Call 999 now if any emergency warning sign is present.
    Call 999 if you collapse, are not breathing, cannot be woken within 1 minute, have not fully recovered after fainting, have chest pain, a pounding or irregular heartbeat, severe breathlessness, serious injury from a fall, seizure-like shaking, new speech or movement difficulty, or fainted while exercising or lying down.

  4. If you are pregnant and feel very faint, recover on your side.
    This is especially important if you are more than 28 weeks pregnant. Get urgent medical advice if you faint, have pain, bleeding, severe shortness of breath, or do not quickly improve.

  5. If you are fully awake and can swallow, take small sips of water.
    This is most relevant if you have been hot, unwell, vomiting, had diarrhoea, exercised hard, or not had much to drink. Do not eat or drink if you are drowsy, confused, choking, or actively vomiting.

  6. Re-check once after you have settled.
    Rest quietly for a few minutes, keep sitting or lying safely, fit the cuff as the monitor instructions say, and take one repeat reading. Do not let repeated checking keep you standing, rushing, or panicking.

  7. Remove likely immediate triggers you can stop now.
    Stay out of a hot bath or shower, stop exercising, avoid alcohol, move to a cooler place if overheated, and stand up only slowly when the faint feeling has clearly passed.

  8. Get same-day medical advice if it persists, recurs, or is unexplained.
    Seek same-day advice if you fainted, still feel weak or lightheaded after resting and fluids, keep getting low readings with symptoms, recently changed medicines, or cannot identify an obvious temporary trigger. Use the urgent medical advice route for your UK nation, such as NHS 111 online in England or NHS 24 111 in Scotland, or contact your GP out-of-hours service.

What can wait

  • You do not need to work out the exact cause right now.
  • You do not need to keep checking your blood pressure every few minutes.
  • You do not need to decide whether a medicine is the cause without clinician advice.
  • You do not need to make long-term diet, exercise, or treatment plans while you feel faint.

Important reassurance

A weak or lightheaded feeling with a low reading can be frightening, and the immediate priority is simple: prevent a fall, let your body settle, and watch for warning signs. Temporary triggers such as heat, standing up quickly, dehydration, illness, or missed food can play a part, but symptoms that persist, recur, or feel severe should be checked.

Scope note

These are first steps to reduce immediate risk and help you decide whether urgent help is needed. Later decisions about causes, medicines, repeated readings, or tests may need a GP, pharmacist, midwife, or another appropriate clinician.

Important note

This is general information, not a diagnosis, medical advice, or a substitute for urgent professional help. If you feel severely unwell, collapse, have chest pain, severe breathlessness, new speech or movement problems, or cannot stay awake, call 999.

Additional Resources

Closely connected guides that may be useful during the same situation or its immediate aftermath.

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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