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Home > Health Library > Tests for Erection Problems
Tests for erection problems can help find out why a man can't have or maintain an erection. This problem is called erectile dysfunction, or impotence. It's a common male problem. Most erection problems are caused by a mix of blood vessel, nerve, or psychological issues.
To find the cause, your doctor will first ask about your sexual history and do a physical exam. During this exam, the doctor will:
Other tests that may be done as part of the exam include:
If the results of your physical exam and other tests are normal, your doctor may have you try a medicine that helps cause an erection. If the medicine doesn't help, then you may need more tests.
This topic focuses on three more tests you may have after the physical exam and lab tests listed above. These three tests are:
The NPT test checks to see if a man is having normal erections during sleep. Most men have 3 to 5 full erections during deep sleep. Men who don't have erections because of psychological problems can still have erections during deep sleep. Sometimes, sleep problems or serious depression can prevent these normal nighttime erections.
This test can be done at home or in a special sleep lab.
Tests are usually done for at least 2 nights in a row. If good erections occur during sleep, the cause of the erection problems is most likely not physical.
The NPT test may also be called the stamp test or the rigidity test.
During this test, the doctor injects a medicine into the side of the penis to make an erection. The fullness of the erection and how long the erection lasts are measured.
Doppler ultrasound uses a handheld tool that is passed gently over the penis. The tool uses reflected sound waves to show blood flow on a computer screen.
The results of your tests may show which kind of treatment is a good choice for you.
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Tests for erection problems are done to help find out if the cause of an erection problem is physical, psychological, or both.
Physical causes include:
Psychological tests may be needed if no physical cause is found for an erection problem. Psychological causes of erection problems may include:
Before the test, do not take any medicines that cause an erection. These medicines include sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra).
Do not drink alcohol or take sleeping pills for 2 days before you have an NPT test. The alcohol and the pills can change your deep sleep time. This can affect nighttime erections.
Tell your doctor if you:
You may be asked to avoid products with nicotine (cigarettes, chewing tobacco) for 30 minutes to 2 hours before the test.
It is helpful if you wear briefs-type underwear (not boxer shorts) with a fly front when you are ready for bed. Put your penis through the fly front. Keep your pubic hair inside the underwear out of the way. Put the device around your penis. After you put on the device, carefully put your penis inside your underwear.
The types of devices you can use include:
This test is generally done by a urologist in the office or clinic. For this test, you will need to take off all of your clothes below the waist. You will be given a cloth or paper gown to use.
While you sit or stand, your penis will be cleaned with a special soap. Then your doctor will inject a medicine into the side of your penis with a small needle. Your doctor may massage the penis for a few seconds to help spread the medicine in the penis. Some doctors may use a band that is gently tightened around the base of the penis for 5 minutes after the medicine is given. The band is to make sure an erection occurs.
A low dose of the medicine is used at first. If the low dose does not cause an erection, then a larger dose may be used. An erection should occur within 5 to 10 minutes after the medicine is given.
A similar medicine may also be placed into the urethra, the tube through which urine leaves the penis. This is called an intraurethral injection.
The medicine may also be given in a thin tablet that is put in the urethra.
After the medicine is given, you may be asked to watch sexually arousing movies or to massage your penis to cause an erection. Your doctor will measure how rigid the erection is and how long it lasts. After the test, your doctor may inject a second medicine to make sure your erection goes away.
The Doppler ultrasound test is done by a urologist or ultrasound technician.
You will lie down on an exam table. Your doctor may need to inject a medicine or use a soft band around the penis to cause an erection. This lets the doctor see blood flow through the vessels.
An NPT test does not cause any discomfort. But you may feel embarrassed about doing the test. Remember that it's important to find the reason you are not able to have an erection. You don't need to feel embarrassed.
During the test, you will feel a sharp sting in your penis from the needle. If you feel a burning or aching pain during the erection, tell your doctor right away.
The ultrasound does not cause any pain. If you get a medicine or device during the test to cause an erection, you may feel embarrassed. The shot may hurt a bit.
There are no problems from having the NPT test.
This test has a small chance of causing:
There are no problems from an ultrasound test. If a device is used to cause an erection, you may have some mild pain. If a shot of medicine is used, you have the same chance for problems as the intracavernosal injection test.
Tests for erection problems can help find out why a man can't have or maintain an erection. This problem is called erectile dysfunction, or impotence.
Tests for erection problems may include blood tests for testosterone, luteinizing hormone, prolactin, and thyroid hormone. A urine test, complete blood count, blood sugar level, and cholesterol and triglyceride levels may also be done.
To learn more about lab tests done for erection problems, see:
An erection has likely occurred if:
An erection has likely not occurred if:
The test is more accurate if repeat tests show the same results.
An erection is usually measured on a scale of 0 to 4. A full erection is a 4.
The ultrasound can show if you have blood flow problems as the cause of your erection problems.
You may not be able to have the test, or the results may not be helpful, if:
Other Works Consulted
Bella AJ, Lue TF (2008). Male sexual dysfunction. In EA Tanagho, JW McAninch, eds., Smith's General Urology, 17th ed., pp. 589–610. New York: McGraw-Hill.
Burnett AL (2012). Evaluation and management of erectile dysfunction. In AJ Wein et al., eds., Campbell-Walsh Urology, 10th ed., vol. 1, pp. 721–748. Philadelphia: Saunders.
Current as of: May 28, 2019
Author: Healthwise StaffMedical Review: E. Gregory Thompson, MD - Internal MedicineAdam Husney, MD - Family MedicineChristopher G. Wood, MD, FACS - Urology
Current as of:
May 28, 2019
Medical Review:E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & Christopher G. Wood, MD, FACS - Urology
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