Diagnosing erectile dysfunction starts with a conversation about your symptoms, followed by a short questionnaire, blood tests, and a physical exam. Most men get a clear answer from these basic steps alone. Advanced imaging or overnight monitoring is only needed when the cause remains unclear or surgery is being considered.
The Symptom Questionnaire
One of the first things you’ll encounter is a standardized questionnaire called the International Index of Erectile Function (IIEF-5). It consists of five questions that ask you to rate, on a scale, how reliably you can get and maintain an erection, how confident you feel about it, and how satisfying intercourse has been. Your answers produce a score that tells your doctor not just whether ED is present but how severe it is. The questionnaire also serves as a baseline, so your doctor can track whether treatment is working later on.
The five questions cover: your confidence in getting and keeping an erection, how often erections are firm enough for penetration, how often you can maintain the erection during intercourse, how difficult it is to maintain it to completion, and how often intercourse is satisfactory overall. It takes about two minutes to complete and is often handed to you on a clipboard before you even see the doctor.
Medical and Sexual History
Your doctor will ask detailed questions about when the problem started, whether it came on gradually or suddenly, and whether you still get erections in certain situations (for instance, in the morning or during sleep). A sudden onset with erections preserved in some contexts often points toward a psychological cause, while a slow, progressive decline is more typical of a physical one.
Expect questions about medications you take, since blood pressure drugs, antidepressants, and several other common prescriptions can contribute to ED. Your doctor will also ask about smoking, alcohol use, physical activity, diet, stress, and relationship factors. Depression and anxiety screening may be part of this conversation, because both conditions are closely linked to erectile problems.
This history matters for another reason: erectile dysfunction that develops organically in men over 30 is now considered a potential early warning sign for cardiovascular disease. Research from the Princeton III Consensus panel found that the typical window between the onset of ED and a cardiac event is two to five years. Because of this, your doctor may treat the visit as an opportunity to screen for heart disease risk factors you didn’t know you had.
Blood Tests
A standard ED workup includes several blood draws, most of which need to happen in the morning.
- Testosterone. A morning blood sample measures your total testosterone level. The AUA defines deficiency as a total testosterone below 300 ng/dL combined with symptoms like low libido, fatigue, or loss of body hair. Because testosterone peaks around 8 a.m., the draw should happen as early in the day as possible. If the first result comes back low, your doctor will usually repeat it on a separate day to confirm. Free or bioavailable testosterone may also be checked, since that reflects the portion your body can actually use.
- Blood sugar. Fasting glucose and hemoglobin A1c reveal whether diabetes or prediabetes is present. Uncontrolled blood sugar damages the small blood vessels and nerves involved in erections, making it one of the most common physical causes of ED.
- Lipid panel. Total cholesterol, LDL, HDL, and triglycerides help assess your cardiovascular risk. High cholesterol accelerates plaque buildup in arteries, including the ones that supply the penis.
- Additional markers. Depending on your symptoms, your doctor may also check prolactin (a hormone that, when elevated, can suppress sexual function), thyroid function, kidney function, and a basic chemistry panel.
A urinalysis is also commonly performed. The presence of protein, glucose, or blood cells in your urine can flag kidney disease, undiagnosed diabetes, or other conditions that contribute to ED.
Physical Examination
The physical exam checks three systems: vascular, neurological, and genital. Your doctor will measure blood pressure, listen to your heart, and feel for pulses in your groin and feet. Weak or absent pulses can indicate reduced blood flow from arterial disease. Waist circumference and BMI are often recorded as part of cardiovascular risk screening.
A genital exam checks the penis for structural abnormalities like Peyronie’s disease, which causes scar tissue that can interfere with erections. The testicles are examined for size and firmness, since small or soft testicles can signal low testosterone production. A brief neurological check, such as testing sensation in the genital area, helps determine whether nerve damage from diabetes, spinal injury, or surgery might be involved.
When Advanced Testing Is Needed
Most men don’t need anything beyond the steps above. Advanced tests are reserved for specific situations: when the diagnosis is uncertain, when initial treatment has failed, when surgery is being planned, or when a doctor needs to distinguish between a physical and psychological cause.
Penile Doppler Ultrasound
This is the most common advanced test. After a medication is injected into the base of the penis to trigger an erection, an ultrasound probe measures blood flow in and out of the penile arteries. The key measurement is peak systolic velocity, which reflects how much blood is flowing in. European guidelines consider a reading above 30 cm/s normal, though some research suggests a threshold of 35 cm/s may be more accurate for men with ED. The test also measures how well blood is being trapped inside the penis. If blood flows in adequately but drains out too quickly (a condition called venous leak), the ultrasound will show that.
Nocturnal Penile Tumescence Testing
Healthy men typically have three to five erections during sleep, each lasting 25 to 35 minutes. A device worn overnight (sometimes called a RigiScan) records the number, duration, and firmness of these erections. If full, rigid erections occur during sleep, the blood vessel and nerve pathways are working properly, which strongly suggests the ED has a psychological cause. If nocturnal erections are weak or absent, a physical cause is more likely.
This test has limitations. Conditions like diabetes, high blood pressure, kidney disease, and sleep disorders can impair nocturnal erections even in men whose ED is primarily psychological. Home monitoring devices also can’t verify sleep quality, which affects the reliability of results. For these reasons, nocturnal testing is used less frequently today than it once was, and it’s mainly reserved for cases with genuine diagnostic uncertainty or medicolegal situations.
Injection Test
An intracavernosal injection test involves injecting a medication directly into the penile tissue to trigger smooth muscle relaxation and blood flow. The most commonly used drug for this is alprostadil, the only agent approved for this purpose in the United States. If a full erection develops, it suggests the blood supply is adequate. However, this test alone provides limited information about vascular status, so it’s typically combined with a Doppler ultrasound rather than used on its own.
Cardiovascular Screening as Part of the Workup
Because the arteries supplying the penis are smaller than coronary arteries, they tend to show signs of plaque buildup earlier. This makes ED a potential early marker of heart disease. The Princeton III Consensus recommendations state that any man with organic ED should be considered at increased cardiovascular risk until testing suggests otherwise.
As part of a thorough ED evaluation, your doctor may order a resting electrocardiogram, especially if you have high blood pressure or diabetes. The full cardiovascular screening includes checking blood pressure, waist circumference, BMI, fasting glucose, kidney function, and lipid levels. Family history matters too: a father who had a heart attack before age 55 or a mother before 65 raises your risk profile. If your ED evaluation uncovers cardiovascular risk factors, addressing them (through lifestyle changes, weight loss, or medication) often improves erectile function as well.
What Testing Won’t Be Done
Certain specialized neurological tests, such as pudendal nerve conduction studies and cavernous electromyography, exist but are not recommended outside of research settings according to AUA guidelines. These tests are technically complex, not widely available, and don’t reliably change treatment decisions for typical patients. If your doctor suspects nerve damage, the clinical history and basic physical exam findings are usually sufficient to guide the next steps.