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Erection Self-Test


An erection self-test is a method to determines a man's ability or inability to achieve an erection during sleep.

Alternative Names

Nocturnal penile tumescence (NPT) stamp test; Nighttime penile tape test

How the test is performed

A strip of four to six postage stamps (any kind) is used for each test. The test needs to be done for 3 nights. The man needs to wear brief-type undershorts that have a fly. Place the penis through the fly, leaving most of the pubic hair against the body.

Wrap the strip of stamps snugly around the shaft of the penis. The stamps need to overlap so the overlapped stamp can be moistened to seal the ring. When the stamp has dried, carefully place the penis back inside the shorts and wear them while sleeping. (They help protect the stamps from falling off).

In the morning, check to see if the stamp ring has been broken along the perforations. If the tearing of the stamps awakens the man during the night, check for an erection and how rigid the erection is.

How to prepare for the test

You will need to buy some stamps. Do not drink alcohol or take a sleep-inducing or sedative medication for at least 2 days before the test.

How the test will feel

The stamps may feel unusual. The test should be done until 3 nights of comfortable, uninterrupted sleep is achieved.

Why the test is performed

The test is done to confirm if a man can have an erection at night. All men with normal physiological erectile function will have an erection during normal sleep. The test may help determine if the cause of erectile dysfunction is psychological or physical.

Normal Values

During at least one of the nights, the ring of stamps is broken between any two stamps.

What abnormal results mean

If the stamp ring is broken, it means that erection problems while you are awake may be the result of a psychological cause.

If the stamp ring does not break on any of the 3 nights it may be a sign that the erection problem is related to physical conditions or medications. You should make an appointment to see a doctor. See also: Impotence

What the risks are

There are no risks.

Special considerations

This test is rarely done anymore. It test is not very accurate and there are better tests available to monitor blood flow. This test does not indicate many important factors of sexual dysfunction, such as quality, duration, or number of erections during the night.


Lue TF, Broderick GA. Evaluation and management of erectile dysfunction and premature ejaculation. In: Wein AJ, ed. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 22.

Moore DP, Jefferson JW. Erectile dysfunction. In: Moore DP, Jefferson JW, eds. Handbook of Medical Psychiatry. 2nd ed. Philadelphia, Pa: Mosby Elsevier; 2004:chap 100.

Review Date: 9/22/2009

