How is ED diagnosed? The history, exam, blood tests and specialist tests explained

In short: an erectile dysfunction evaluation starts with a conversation and an exam. A clinician asks about your health, your medicines, your sex life and how you are feeling, examines you, and orders selected blood tests. Some men, generally those with more complex histories, may also need specialist tests: an ultrasound that shows blood flow, a test that records erections during sleep, or an injection test done in the office (NIDDK, Diagnosis of ED; AUA Erectile Dysfunction Guideline, J Urol 2018). Each step is one clue among several. This page walks through what each one involves and what it can and cannot tell a clinician. It is educational information, not medical advice.

How do doctors diagnose erectile dysfunction?

Doctors diagnose erectile dysfunction with three tools: your medical, sexual and mental health history, a physical exam, and lab and other tests. That is how the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) describes it, and it notes that health care professionals including urologists do this work (NIDDK, Diagnosis of ED). The American Urological Association (AUA) guideline says the same in its first statement: men with symptoms of ED should have a thorough medical, sexual and psychosocial history, a physical examination, and selective laboratory testing (AUA Guideline, Statement 1).

The goal is to find the cause, not only to confirm the symptom. ED itself is defined simply: trouble getting or keeping an erection that is firm enough for sex (NIDDK, Definition & Facts). What sits behind it varies. NIDDK lists conditions that affect blood vessels, nerves or hormones, certain medicines, mental or emotional issues, and lifestyle behaviors among the possible causes (NIDDK, Symptoms & Causes). The evaluation is how a clinician narrows that list down for you. If you are still deciding whether to book it, our guide on when to see a doctor about ED is the starting page of our getting care section. If you live with multiple sclerosis, a spinal cord injury or diabetes, our guide to nerve conditions and ED covers what that history adds to the evaluation.

One honest note about the evidence: the AUA panel found too little research to build an evidence base for ED diagnosis in practice, so its diagnosis section rests mainly on clinical principles and expert opinion (AUA Guideline, Evaluation and Diagnosis). That is why the steps below describe a framework that clinicians adapt, not a fixed checklist.

What questions does a doctor ask about ED?

A doctor asks about your general health, every medicine you take, your sexual function and your mental health. NIDDK says clinicians may ask about prescribed and over-the-counter medicines, vitamins and supplements, and that they also ask about your mental health and the emotions you are feeling. They may ask your partner about your relationship and how it affects your ED (NIDDK, Diagnosis of ED).

The AUA guideline adds detail. General history factors include age, other medical and psychological conditions, past surgeries, medications, family history of vascular disease and substance use. Key ED questions include when symptoms began, how severe they are, how much they bother you, whether the problem is getting an erection, keeping it or both, whether it happens only in certain situations, whether you have nighttime or morning erections or erections with masturbation, and what you have tried before (AUA Guideline, J Urol 2018).

Because many men are uncomfortable raising sexual concerns with a physician, the guideline says it is critical that the physician starts the conversation (AUA Guideline, Statement 1). It also recommends validated questionnaires to assess how severe ED is, to measure how well treatment works and to guide later management, and names the Erection Hardness Score and the Sexual Health Inventory for Men as short-form examples (AUA Guideline, Statement 2). You do not need clinical words. Describing what changed is enough to start.

Why are desire, erection and climax asked about separately?

Desire, erection and climax are asked about separately because they are different parts of sexual response, and changes in one can be mistaken for another. NIDDK says your clinician will review your sexual activity with questions about climax, ejaculation, erection and sexual desire (NIDDK, Diagnosis of ED).

The AUA guideline explains the framework. It describes sexual response as a series of phases, characterized by Masters and Johnson as desire, arousal, orgasm and resolution, and it places ED in the arousal phase (AUA Guideline, Executive Summary). The guideline adds that problems with arousal can have knock-on effects on sexual interest and orgasm, and that men may confuse changes in desire, orgasm or ejaculation with ED, which is why it calls for careful, detailed questions (AUA Guideline, Statement 1). So low interest in sex is a different question from erections that are not firm enough, and a change in climax or ejaculation is a third one. If desire is the main thing that has changed, say so. That answer points the conversation somewhere different, and it is the kind of detail that helps a clinician understand and diagnose the problem.

How do mental health and relationships fit into the evaluation?

Mental health and relationships are part of the standard evaluation, because they can matter on their own or alongside a physical cause. NIDDK says some mental health or emotional issues, such as anxiety, stress or depression, can either cause ED or make it worse (NIDDK, Symptoms & Causes). The AUA guideline says psychological factors such as depression, anxiety and relationship conflict may be primary or secondary contributors, and that discussing them with men and their partners is a key part of patient education (AUA Guideline, J Urol 2018).

The guideline also notes that the cause of ED is often multifactorial (AUA Guideline, Statement 1), so these questions sit alongside the exam and tests rather than replacing them. Our guide to ED vs performance anxiety covers how the two can overlap.

What does the physical exam for ED check?

The physical exam often checks for blood vessel and nervous system problems, hormonal problems, and injury or physical problems with the penis, such as Peyronie’s disease, according to NIDDK (NIDDK, Diagnosis of ED).

The AUA guideline lists the specifics: vital signs including pulse and resting blood pressure, and a genital exam that looks at the skin of the penis and the position of the urethral opening and feels for hidden deformities or plaques. It notes that feeling a plaque, or not feeling one, is not on its own definitive evidence of Peyronie’s disease, and that further tests follow if that is suspected. It also says a digital rectal exam is not required to evaluate ED, although enlarged prostate is a common companion condition in men with ED that may merit its own evaluation and treatment (AUA Guideline, J Urol 2018).

Why does the clinician check blood pressure, weight and the prostate?

Because ED often travels with other conditions, and the exam is a chance to look for them. The AUA guideline lists vital signs, including pulse and resting blood pressure, as part of the exam (AUA Guideline, J Urol 2018). The European Association of Urology (EAU) guideline adds that blood pressure and heart rate should be measured if they have not been checked in the previous three to six months, and that body mass index or waist size should be measured to look for related conditions such as metabolic syndrome (EAU Guidelines, Management of ED).

The prostate comes up for a different reason. NIDDK lists prostate tests among the blood tests a clinician may use (NIDDK, Diagnosis of ED), and the AUA guideline notes that an enlarged prostate is a common companion condition in men with ED, even though a rectal exam is not required to evaluate ED itself (AUA Guideline, J Urol 2018). Our guide to an enlarged prostate and ED covers how the two overlap.

What blood tests are done for erectile dysfunction?

Blood tests for ED are selective, and the one the AUA recommends for every man with ED is a morning total testosterone level (AUA Guideline, Statement 4). NIDDK says a clinician may use blood tests including thyroid tests and prostate tests to help find the cause (NIDDK, Diagnosis of ED). Our guide to thyroid problems and other hormone causes of ED explains what those thyroid tests look for.

The AUA guideline is candid about the limits here. Apart from possibly testosterone, blood sugar (glucose or hemoglobin A1c) and, in some cases, blood fats (lipids), it says no routine blood test is likely to change how ED is managed, although blood tests can still point to a cause or reveal other conditions that need treatment. It adds that thyroid function tests and PSA may be appropriate for some men. Testosterone is measured to check for testosterone deficiency, which the guideline defines as a total testosterone below 300 ng/dL together with symptoms and signs, so a number on its own does not make the diagnosis (AUA Guideline, J Urol 2018). Because levels move through the day, the guideline says samples should ideally be taken in the morning and that at least two morning measurements are needed before diagnosing testosterone deficiency (same source). Our page on ED and low testosterone goes further into how the two relate, and our guide to erectile dysfunction tests explains each test by name, including what at-home kits can and cannot show.

The blood sugar and cholesterol checks connect to a wider point. The AUA says men should be told that ED is a risk marker for underlying cardiovascular disease and other health conditions that may warrant evaluation and treatment (AUA Guideline, Statement 3). The guideline is careful with that term: a risk marker predicts a higher chance of a disease but is not part of its cause. ED does not diagnose heart disease. It is a reason to look. Our guide to what ED can signal about your health covers those links.

Can you have ED with normal blood tests?

Yes. Normal blood tests are useful information, but they do not rule out ED or explain every case. Blood tests look for things such as low testosterone, high blood sugar or a thyroid problem. Many causes of ED do not show up in a blood panel at all: NIDDK lists nerve damage, pelvic surgery, many common medicines, anxiety, depression and stress, and lifestyle factors such as smoking and drinking too much alcohol among them (NIDDK, Symptoms & Causes). NIDDK also says plainly that “sometimes, the exact cause of ED is not known,” in which case clinicians focus on improving sexual function (NIDDK, Treatment for ED).

So a normal result does not mean the symptoms are not real. It means the answer is more likely to come from the history, the exam, a review of your medicines, or, for some men, the specialist tests below. The AUA guideline says specialized testing may be needed for some men, generally those with complex histories (AUA Guideline, Statement 5). If worry or mood seems to be part of the picture, our guide to ED vs performance anxiety covers that side.

What does a penile ultrasound show?

A penile ultrasound shows how blood flows through the penis. NIDDK lists ultrasound imaging for exactly that purpose, as one of the lab and imaging tests a clinician may use to help find the cause of ED (NIDDK, Diagnosis of ED).

The AUA guideline names penile duplex ultrasound among its specialized tests and notes that it may be combined with an injection test to give a more detailed, measured picture of how the penis’s blood vessels respond (AUA Guideline, J Urol 2018). Like every test on this page, it is one clue among several and is not part of every evaluation.

What is a nighttime erection test?

A nighttime, or nocturnal, erection test checks for the erections you have while you sleep. NIDDK says the test can help a clinician know whether ED is due to a physical problem, and that it can be done at home or in a sleep lab (NIDDK, Diagnosis of ED). The AUA guideline lists it as nocturnal penile tumescence and rigidity testing among its specialized tests (AUA Guideline, J Urol 2018).

The same idea shows up in the history. The guideline says that having nighttime or morning erections suggests, but does not confirm, a psychogenic (psychological) component that would benefit from further investigation (AUA Guideline, J Urol 2018). That wording matters: it is a pointer for the clinician, not a verdict you can reach on your own. The EAU guideline adds that the test is usually done over at least two separate nights, and that men with psychogenic ED usually have normal results, while noting limits such as how well nighttime erections reflect erections during sex (EAU Guidelines, Management of ED). Our guide to morning erections covers what they can and cannot tell you.

What is the in-office injection test for ED?

The injection test, also called an intracavernosal injection test, checks whether the penis can get an erection. NIDDK describes it this way: a health care professional injects a medicine into the penis to see how full the penis gets and how long an erection lasts, and the test is usually done in the office (NIDDK, Diagnosis of ED).

The AUA guideline gives it a specific role. Statement 17 says that for men with ED who are considering injection therapy, an in-office injection test should be performed (AUA Guideline, Statement 17). It also lists the injection test among the specialized tests for some men with complex histories, sometimes paired with duplex ultrasound (AUA Guideline, J Urol 2018). It is not a routine first step for everyone.

Does every man with ED need every test?

No. The history, exam and selected blood tests are the standard starting point, and specialist testing is for some men only. The AUA guideline says specialized testing and evaluation may be necessary for some men with ED to guide treatment, generally those who present with complex histories (AUA Guideline, Statement 5). It adds that specialized testing should only occur if the findings will affect management. The specialized tests it discusses are nighttime erection and rigidity testing, the injection test, penile duplex ultrasound, cavernosometry and selective internal pudendal angiography (AUA Guideline, J Urol 2018). NIDDK’s wording points the same way: clinicians “may use” lab, imaging and other tests (NIDDK, Diagnosis of ED).

The EAU guideline lists the situations in which specific tests are usually considered: ED present from the start of sexual life, younger men with a history of pelvic or perineal injury who might benefit from vascular surgery, penile deformities that might need surgery such as Peyronie’s disease, complex psychiatric or psychosexual problems, complex hormone disorders, a request from the patient or partner, and medico-legal reasons (EAU Guidelines, Management of ED).

What does each part of the evaluation add?

Each step answers a different question, which is why no single one is enough on its own.

Sources: NIDDK, Diagnosis of ED; AUA Guideline, Statements 1 to 5 and 17; EAU Guidelines, Management of ED.

Which doctor diagnoses ED?

Several kinds of clinician can. NIDDK says health care professionals, including urologists, diagnose ED (NIDDK, Diagnosis of ED), and the AUA guideline describes specialist testing for some men, generally those with complex histories (AUA Guideline, Statement 5). Our guide to which doctor treats ED covers who does what, and talking to a doctor about ED helps you prepare: describing what changed, when it started, and whether it is desire, erections or climax that is different is enough to begin. If you are not sure whether what you are noticing counts as ED, our guide to ED symptoms sets out the patterns.

Which tests fit your situation is a conversation for a licensed clinician. If you are still deciding whether to book that conversation, our guide on when to see a doctor about ED covers the signs that make a visit worth prioritizing.

Sources

Every clinical statement on this page traces to a primary or guideline source:

• NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases), Diagnosis of Erectile Dysfunction, last reviewed October 2024. The medical, sexual and mental health history; the physical exam; blood tests including thyroid and prostate tests; ultrasound of penile blood flow; the nocturnal erection test; and the in-office injection test: niddk.nih.gov, ED diagnosis
• NIDDK, Definition & Facts for Erectile Dysfunction, last reviewed October 2024. Definition of ED: niddk.nih.gov, ED definition and facts
• NIDDK, Treatment for Erectile Dysfunction, last reviewed October 2024. “Sometimes, the exact cause of ED is not known”: niddk.nih.gov, ED treatment
• European Association of Urology, Guidelines on Sexual and Reproductive Health, Management of Erectile Dysfunction. Blood pressure, heart rate and body measurements at the exam; nighttime erection testing over at least two nights and its limits; indications for specific diagnostic tests: uroweb.org, Management of ED
• NIDDK, Symptoms & Causes of Erectile Dysfunction, last reviewed October 2024. Causes involving blood vessels, nerves, hormones, medicines, mental or emotional issues and lifestyle: niddk.nih.gov, ED symptoms and causes
• Burnett AL, et al. Erectile Dysfunction: AUA Guideline. J Urol 2018;200:633. Statements 1 to 5 and their discussion (history, questionnaires, risk marker counseling, morning testosterone and morning sampling, specialized testing), the physical exam and laboratory discussion, and Statement 17 (in-office injection test): auajournals.org, AUA ED guideline
• American Urological Association, Erectile Dysfunction (ED) Guideline (2018), web version. Executive summary (phases of sexual response, ED as an arousal-phase impairment) and the evidence note for the diagnosis section: auanet.org, ED guideline