Fainting during urination (micturition syncope): What causes it?

Date Updated: 04/17/2020

Answer Section

Micturition (or post-micturition) syncope is fainting during or, more commonly, immediately after urination due to a severe drop in blood pressure. Micturition syncope is most common in older men and usually occurs at night after a deep sleep.

The exact cause of micturition syncope isn't fully understood. But it may be related to opening (vasodilation) of the blood vessels that occurs when getting up and standing at the toilet or that occurs at the rapid emptying of a full bladder. This is thought to result in a sudden drop in blood pressure.

Other factors that may play a role in micturition syncope include:

Alcohol
Hunger
Fatigue
Dehydration
Medical conditions, such as a respiratory infection
Use of alpha blockers to improve urination in men with prostate problems

Preventing micturition syncope

Micturition syncope is uncommon and should be evaluated by a doctor because it may indicate an underlying medical condition. Prevention of micturition syncope depends on recognizing the factors that contribute to micturition syncope and avoiding them.

Some strategies you might suggest to your husband to avoid micturition syncope and possible resulting injury are:

Avoid excessive drinking of alcohol
Don't get out of bed suddenly — first, sit on the edge of the bed and move your legs, making sure you aren't dizzy or lightheaded
Urinate sitting down
Ask your doctor whether any medications you're taking may be causing your condition

As much as possible, ensuring the floor from your bed to the bathroom is carpeted or padded also is a good strategy for avoiding injury from a potential fall.