What is an overnight erection test?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
An overnight erection test is just what it sounds like: a way to determine whether you have one or more erections while you are sleeping. You may not be aware that you do. The medical term for the test is nocturnal penile tumescence (NPT) but whatever it is called, it's a simple test that you can do at home. You'll affix several postage stamps to your penis, so that they form a ring around it. In the morning, if the seal is broken, it's a pretty good indication that you had one or more erections. That in turn may be a clue that your erection problems aren't caused by physical blood flow problems but may be more psychological in nature. Therapy, either individually or with your sexual partner, may be an effective approach in that case.  If you are uncomfortable doing this at home,  the NPT can also be done in a sleep lab using a simple ring-like device called a snap gauge. Whichever test your doctor decides to use, both can give more detail about your erections at night.  
Men typically have three to five erections while sleeping. The Nocturnal penile tumescence (NPT) is an overnight test to determine whether these erections are occurring.

If you do not have erections while you sleep, the doctor will look for a health condition or medication that decreases blood flow to the penis or interferes with nerve signals that enable arousal and erection. If you experience erections in your sleep or upon awakening, your erectile dysfunction (ED) may be caused by stress or depression.

The NPT test is done two ways: the strain gauge method and the snap gauge method. The strain gauge method documents changes in circumference when elastic bands on the base and tip of the penis stretch during an erection. The snap gauge method measures erectile function with pressure-sensitive bands that break an erection occurs.

Whatever the cause of your ED, your doctor can recommend treatment that will help. 

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.