No particular tests are there to diagnose the impotence but still blood tests are done to diagnose the underlying problems which could be obesity, thyroid level disturbances, some heart diseases and other disorders like hypogonadism and decreased levels of growth hormone and sex hormones. Generally the diagnosis is by the physical examination and is based on the symptoms.

  

Doctor can easily find it out that the impotence is either due to some organic reason or due to some psychological reasons. If a patient of erectile dysfunction has a previous erection which has not created any problems then it is a case of psychological erectile dysfunction and the doctor will think on that grounds.

Investigations and Tests to Diagnose Erectile Dysfunction

• Duplex ultrasound - It is used to evaluate blood flow, venous leak, signs of atherosclerosis, and scarring or calcification of erectile tissue.  By Injecting prostaglandin, a stimulator produced in the body, causes erection.  Then ultrasound is used to see vascular dilation and measure penile blood pressure. All the measurements are compared with flaccid penile state measurements.
• Penile nerves functions Tests - These tests are used to determine if there is sufficient nerve sensation in the penis. The tests include bulbocavernous response.  While squeezing the glans of the penis contraction will be seen in anus if nerve functions are normal. Using this procedure the doctor will examine if there is a delay in the two responses accordingly a doctor will make some interpretations. Particular nerve tests are performed in patients with suspected nerve damage due to diabetes or other nerve disorders.
• Nocturnal penile tumescence Test - Normally a man has five to six erections during sleep when the man will be in rapid eye movement sleep phase. The absence of erections indicates a problem with nerve function or blood supply in the penis. Using snap gauge and strain gauge technique penile rigidity and circumference during nocturnal erection is measured and interpreted.
• Penile biothesiometry Test - Using electromagnetic vibration sensitivity and nerve function in the glans and shaft of the penis are evaluated and interpreted. Decreased feel of vibrations indicates nerve damage in the pelvic region leading to impotence. 
• Penile Angiogram Test - It is performed to visualize the blood circulation inside the penis. This test also has value in treatment of Priaprism. 
• Dynamic Infusion Cavernosometry Test - Fluid is injected in penis in this test at a known volume and pressure and the results are interpreted. Prostaglandins have value in the procedure of this test. 
• Corpus Cavernosometry Test - Test is based on complex fluid dynamics. In this test fluid is injected into the penis and later using some calculations of flow dynamics venous leakage is worked out. 
• Digital Subtraction Angiography Test - Digital images are taken in a dark room and the blood vessels are studied using this technique. 
• Magnetic resonance angiography Test - It works on the principles of magnetic field and generally produces high quality and detailed images which are very helpful for a clinician. Sometimes a contrast medium can also be used to enhance the images.