Is ED Related to Low Testosterone? What the Trials Show

Sometimes, but low testosterone is far from the most common cause. Testosterone mainly drives sexual desire, and a clear deficiency can also contribute to erection problems. A 2014 systematic review concluded that evidence supports testosterone treatment for men who have both ED and true hypogonadism, while noting the benefit-risk balance is uncertain at advanced ages.⁵ Where testosterone is normal, the same review's logic points elsewhere, and the largest trials of testosterone treatment give no reason to expect an erection benefit from raising a normal level.^1,2

How does testosterone affect erections?

Testosterone acts at several points in the erection pathway. A 2014 systematic review described it as modulating nearly every component involved, from pelvic nerve ganglia to smooth muscle and the endothelial cells of the penis, and as coordinating the timing of an erection with sexual desire.⁵ In practice, the clearest day-to-day effect is on desire and sexual thoughts, which is why low testosterone more reliably shows up as low libido than as a mechanical erection problem.

The same review notes that hypogonadism and ED overlap substantially in epidemiologic studies. Overlap is not the same as cause. Diabetes, obesity, heart disease and some medications can lower testosterone and also damage the blood vessels and nerves involved in erections, so the two problems can travel together without one causing the other.^5,6

What does the research say about testosterone treatment for ED?

Three pieces of evidence matter most, and they point in a consistent direction: treatment helps most when testosterone is clearly low, and sexual desire responds more than erections do.

Read together, these results show why the headline "testosterone fixes ED" is too simple. The 2016 trial saw a benefit in erectile function, while the larger, longer TRAVERSE sexual substudy, run in men whose main complaint was low libido, did not. The authors of the 2014 meta-analysis concluded that the role of testosterone is uncertain in men who are not clearly hypogonadal.¹

Would testosterone help if levels are normal?

The evidence does not support it. The 2014 meta-analysis found its positive effects in hypogonadal men and called the role uncertain in men who are not clearly hypogonadal.¹ The Endocrine Society guideline is explicit that testosterone therapy is for men with symptoms and signs of deficiency and unequivocally, consistently low testosterone levels, not for a number within the normal range.⁴

A tadalafil add-on trial makes the same point from the other direction. The TADTEST study enrolled 173 men aged 45 to 80 who had not responded to PDE5 inhibitors and had low or low-normal testosterone. Overall, adding testosterone gel to optimized tadalafil gave no extra benefit over placebo. The differences were significant only in men whose baseline total testosterone was 3 ng/mL (300 ng/dL) or lower.³ Erectile function also kept improving in both groups over at least 12 weeks, which is a reminder that a tadalafil trial needs enough time before it is called a failure.

How is low testosterone actually diagnosed?

A single result is not enough. The Endocrine Society guideline recommends diagnosing hypogonadism only in men who have symptoms and signs consistent with testosterone deficiency and low levels on repeated testing. It recommends a fasting morning total testosterone measured with an accurate assay as the first test, repeated to confirm. When the result is near the lower limit of normal, or a condition alters sex hormone-binding globulin, the guideline suggests measuring free testosterone as well.⁴ The American Urological Association guideline likewise stresses accurate assessment of total testosterone levels together with symptoms and signs.⁸

This matters for two reasons. First, testosterone fluctuates and is highest in the morning, so an afternoon or one-off value can mislead. Second, symptoms such as tiredness, low mood and reduced desire are not specific to low testosterone. Sleep problems, depression, obesity and many medications cause them too.

What else should be checked first?

If testosterone is normal, the usual causes still deserve a look. NIDDK lists diabetes, heart disease, obesity, certain medications, smoking, heavy drinking, and anxiety and stress among the common contributors to ED.⁶ Because ED can precede cardiovascular events, persistent symptoms are worth a checkup of blood pressure, blood sugar and cholesterol, not only a hormone panel.⁹ Our piece on how common ED is at 40 covers the survey data on these risk factors, and common ED myths looks at why "it must be hormones" is a frequent assumption. For how drinking fits in, see alcohol and ED medication.

The first-line medical treatments for ED are PDE5 inhibitors, which do not depend on testosterone level in the same way. The AUA ED guideline lays out the treatment options and the need for a medical and sexual history first.¹⁰ Before any prescription, a clinician needs the full medication list; see questions to settle before an online ED prescription.

What are the risks of testosterone treatment?

Testosterone is not a harmless add-on. The Endocrine Society guideline recommends against starting therapy in men planning fertility soon, and in men with breast or prostate cancer, a palpable prostate nodule, elevated PSA or hematocrit, untreated severe sleep apnea, severe urinary symptoms, uncontrolled heart failure, a recent heart attack or stroke, or thrombophilia. It also advises monitoring symptoms, side effects, testosterone and hematocrit levels, and prostate cancer risk during the first year.⁴ The Testosterone Trials reported similar rates of adverse events in the two groups but said the number of participants was too small to draw conclusions about risk.⁷

Limits of the evidence

Most trials enrolled mixed or older populations, used different testosterone formulations and used different ED scales. The 2014 meta-analysis flagged publication bias. TRAVERSE tested men with low libido, not men chosen for ED, so it cannot say how testosterone performs in a man whose main problem is erections. None of this can tell an individual man whether his symptoms come from low testosterone; that needs repeated, properly timed blood tests and a clinical evaluation.

Your questions

Is erectile dysfunction related to low testosterone?

Sometimes. Testosterone affects sexual desire and several parts of the erection pathway, and low levels and ED often occur together. But diabetes, heart disease, obesity and medications can cause both, so low testosterone is only one of many possible contributors.

Would testosterone help with ED if my levels are normal?

The evidence does not support it. A meta-analysis found benefits in hypogonadal men and called the role uncertain in men who are not clearly hypogonadal, and the Endocrine Society recommends testosterone therapy only for men with symptoms and consistently low levels.

Can you have ED with normal testosterone?

Yes. NIDDK lists many other contributors, including diabetes, heart disease, obesity, certain medications, smoking, heavy drinking, and anxiety or stress. A normal testosterone result does not rule ED out.

Does testosterone treatment improve erections or just libido?

Results are mixed. The 2016 Testosterone Trials reported improved sexual activity, desire and erectile function, while the larger TRAVERSE sexual function study found improved activity and desire but no significant improvement in erectile function.

How is low testosterone diagnosed?

The Endocrine Society recommends symptoms plus consistently low fasting morning total testosterone on repeat testing, with free testosterone checked when the result is near the lower limit of normal.

Read next

• Is ED Common in 40 Year Olds? What the Surveys Actually Show
• Alcohol and ED Medication: What the Labels Actually Say
• 7 ED Myths, Checked Against the Research
• 9 Questions to Ask Before Getting ED Medication Online