Sleep Disorders

Updated 25 November 2014

Why do some men faint when they urinate at night?

There is a strange phenomenon where men faint when they get up at night to urinate. It's called 'micturition syncope'. We take a closer look at why this happens and if it is dangerous.

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Fainting while urinating standing up, particularly just after waking, is quite common for men.

The medical term is micturition syncope. Micturition is the tecnical term for "emptying the bladder" and syncope the term used for fainting as a result of reduced blood flow to the brain. 

When you sleep you have a lower than normal blood pressure because your veins are dilated due to lowered nerve activity. When you get up at night to pass water, the nerves should "kick in" and cause the veins to contract and push up your blood pressure. 

When you pass water, the nerve stimulation involved in relaxing the bladder sphincter and contracting the bladder may lead to a fall in blood pressure, even in "normal" people. 

In micturition syncope the blood pressure doesn't normalise fully when the person gets up, and when that person then starts to pass water he passes out. 

The best would be to have your blood pressure taken, to make sure that you don't have an irregular heartbeat and that you aren't anaemic and that there are no underlying diseases. 

Other factors that could cause micturition syncope include dehydration, excessive alcohol intake, medical conditions such as a respiratory infection and the use of certain medications, including alpha blockers that improve urination in men with prostate problems

If a man has micturition syncope, he should just remember to sit on the bed for 1-3 minutes before walking to the bathroom. It's also a good idea to urinate sitting down. 

Read more:

Understanding dizziness
Fainting could be a sign of heart trouble
What you need to know about kidney and bladder disorders 

Image: man falling over in bathroom, Shutterstock

 

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Sleep disorders expert

Dr Alison Bentley is a general practitioner who has consulted in sleep medicine and sleep disorders, in both adults and children of all ages, for almost 30 years. She also researches and publishes on a number of sleep-related topics both in formal research journals and lay publications including as editor of Sleep Matters, an educational newsletter on sleep disorders for doctors.

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