Top 7 tips on visiting your doctor about fainting

Written by: Dr Boon Lim
Edited by: Cal Murphy

Syncope (pronounced sin-cope-pee), also known as fainting, blacking out or passing out, can be a worrying problem. Many people have experienced this phenomenon, perhaps blacking out when dehydrated or when travelling on crowded public transport. If you have fainted repeatedly, particularly if it has resulted in injury, it is highly advisable to consult your doctor or a specialist. We talked to one such specialist – London-based cardiologist and syncope expert Dr Boon Lim, who leads the renowned Imperial Syncope Diagnostic Unit at Hammersmith Hospital. He gave us his top tips for what to record and tell your doctor about episodes of syncope during your consultation.

Dr Boon Lim’s top tips on what to record for your doctor:

  1. Be very clear about what triggers fainting – this can mean that you have to think back to what was happening in the immediate 3 minutes prior to loss of consciousness. For example, were you standing in a crowded train, did you just get out of the bed to walk to the bathroom, had you just completed a run or exerted yourself physically?
  2. Record the frequency of your symptoms (i.e. how many times a day/week/month).
  3. Record the duration of syncope (i.e. was this 2 seconds, 10 seconds, or 10 minutes?).
  4. Record how you felt immediately after regaining consciousness, including whether you were confused, if you knew where you were, and if you knew who you were with.
  5. Think back to your childhood and teenage years and recall if you experienced syncope, for example, while at church, in assembly, or perhaps during a blood test.
  6. If you have a home blood pressure monitor (you can buy one from any good pharmacy for under £50), please record your blood pressure values first thing in the morning, upon waking, and, if possible, during, or immediately after syncope.
  7. Please write all this information down. It is easy to forget details that may be important for your doctor to know. The strongest memory is weaker than the faintest ink!


Fainting can occur in a variety of situations and is usually the result of low blood pressure and a reduced resistance to blood flow in the peripheral blood vessels. You can learn more about the causes of fainting, the warning signs to watch out for and get some top tips on preventing syncope by visiting Dr Lim’s other articles. 

By Dr Boon Lim

Dr Boon Lim is one of London's leading cardiologists and electrophysiologists. He specialises in heart rhythm disturbances, pacing and syncope at Imperial College and at his Harley Street clinic. He leads the established Imperial Syncope Diagnostic Service at Hammersmith Hospital and is frequently invited to national and international meetings to share his experience. He has a special interest in the mapping and ablation of atrial fibrillation (AF) and is highly-skilled at using modern 3-D mapping technologies. Dr Lim was awarded several prestigious prizes during his medical training at Cambridge University where he obtained a double First Class Honours Degree. He has continued his passion for education and research serving as an Honorary Senior Lecturer at Imperial College where he supervises several PhD students.

Dr Lim is very actively engaged in all aspects of research with a particular interest in developing the best techniques for treating atrial fibrillation. He is invited to speak both nationally and internationally to discuss his findings and to teach other physicians about the best techniques for complex mapping and ablation of atrial fibrillation and other complex arrhythmias. He leads a very active syncope research team based at the Imperial Syncope Diagnostic Unit and is looking to improve healthcare delivery for patients through use of effective online education to help improve the quality of life for patients across the UK. 

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