Testosterone and Erectile Function: What the Trials Show

In men with confirmed low testosterone, testosterone erectile function outcomes improve modestly. Corona’s 2017 meta-analysis in European Urology, pooling 14 placebo-controlled trials and 2,298 men, found a mean difference of 2.31 (95% CI 1.41 to 3.22) on the erectile function domain of the International Index of Erectile Function. Men with the lowest levels gained most.

Key takeaways

• Corona’s 2017 meta-analysis in European Urology, covering 14 placebo-controlled trials and 2,298 men with a mean age of 60.2 years, reported a mean difference of 2.31 (95% CI 1.41 to 3.22) on the IIEF erectile function domain, p less than 0.0001.
• The same 2017 analysis found a larger effect the lower the starting level: 2.95 (95% CI 1.86 to 4.03) in men below 8 nmol/L compared with 1.47 (95% CI 0.90 to 2.03) in men below 12 nmol/L.
• The TestES individual participant data meta-analysis (Hudson 2023, Lancet Healthy Longevity) pooled 35 studies and 5,601 participants and reported an IIEF-15 total difference of 5.52 (95% CI 3.95 to 7.10) and an erectile subscore difference of 2.14 (95% CI 1.40 to 2.89), reaching the minimal clinically important difference for mild erectile dysfunction.
• In the TRAVERSE sexual function substudy (Pencina 2024, Journal of Clinical Endocrinology and Metabolism), sexual activity improved by 0.49 acts per day more than placebo at 6 months, but erectile function specifically did not improve.
• The European Association of Urology guideline, 2026 edition with a limited update in March 2026, recommends testosterone therapy as first-line treatment in hypogonadal patients with mild erectile dysfunction, using a total testosterone of 12 nmol/L as the diagnostic threshold.

How large is the testosterone erectile function effect in trials?

The average improvement is about 2 points on the erectile function domain of the International Index of Erectile Function. Corona’s 2017 meta-analysis in European Urology pooled 14 placebo-controlled randomized trials with 2,298 participants, a mean age of 60.2 years and a mean follow-up of 40.1 weeks, and reported a mean difference of 2.31 (95% CI 1.41 to 3.22) versus placebo, p less than 0.0001.

A second, independent analysis lands close to the same number. The TestES individual participant data meta-analysis (Hudson 2023, Lancet Healthy Longevity) reported an erectile function subscore difference of 2.14 (95% CI 1.40 to 2.89) and stated that this reached the minimal clinically important difference for mild erectile dysfunction. Two separate pooled analyses arriving at roughly the same figure is the main reason this benefit is treated as established rather than provisional.

Do men with the lowest testosterone gain the most?

In Corona 2017, yes. The 2017 European Urology analysis reported an improvement of 1.47 (95% CI 0.90 to 2.03) in men with a total testosterone below 12 nmol/L and 2.95 (95% CI 1.86 to 4.03) in men below 8 nmol/L. The same authors state that the effect was smaller in men with diabetes and obesity.

A published result that points the other way

Hudson 2023 did not find that pattern. In the TestES data set (35 studies, 5,601 participants, with 17 trials supplying raw participant-level data on 3,431 men, median age 67), the benefit did not depend on age, obesity, diabetes, or how low the baseline testosterone was. Both findings are in the published record, they disagree, and a reader deciding what to expect should know that.

What did the largest individual participant data analysis find?

Hudson 2023 reported the broadest sexual function benefit of any analysis in this field. The IIEF-15 total score mean difference was 5.52 (95% CI 3.95 to 7.10), with the erectile function subscore at 2.14 (95% CI 1.40 to 2.89). Aging Males’ Symptoms scores and several SF-12 and SF-36 quality of life subscores also improved.

The same analysis carries two limitations the authors state directly. There was no significant improvement on the Beck Depression Inventory, and men who start with worse symptoms finish at a lower absolute score even though they improve by the same amount as everyone else.

What did the TRAVERSE sexual function substudy find?

Sexual activity improved and erectile function did not. Pencina’s 2024 paper in the Journal of Clinical Endocrinology and Metabolism reported a nested randomized study within TRAVERSE covering 1,161 men with low libido (587 on testosterone, 574 on placebo) drawn from the 5,204-man trial. The between-group difference in sexual activity was 0.49 acts per day (95% CI 0.19 to 0.79) at 6 months and 0.47 (95% CI 0.11 to 0.83) at 12 months, maintained at 24 months, alongside improvement in hypogonadal symptoms and sexual desire.

The authors also report that erectile function specifically did not improve versus placebo in this substudy. The wider trial is covered in the TRAVERSE explainer.

What did the Testosterone Trials find in men aged 65 and older?

They found a consistent sexual benefit and little else. Snyder’s 2016 main paper in the New England Journal of Medicine reported on 790 men aged 65 and older with a serum testosterone below 275 ng/dL and symptoms suggesting androgen deficiency, randomized to testosterone gel or placebo gel for one year, with each man taking part in one or more of three trials covering sexual function, physical function and vitality. Testosterone significantly increased sexual activity on the Psychosexual Daily Questionnaire (P less than 0.001), and significantly increased sexual desire and erectile function.

The same paper found no significant benefit for vitality on the FACIT-Fatigue scale, and the authors state that the number of participants was too few to draw conclusions about the risks of treatment.

The sexual function trial was reported separately and in more detail. Cunningham’s 2016 paper in the Journal of Clinical Endocrinology and Metabolism reported a placebo-controlled randomized trial at 12 US academic centres in 470 men aged 65 and older, in which testosterone significantly improved 10 of 12 measures of sexual activity.

The authors add an important caveat: no threshold testosterone level predicted response, and none of 27 baseline characteristics predicted who would respond.

Does testosterone help erectile function in men with type 2 diabetes?

The effect is smaller in this group. Algeffari’s 2018 meta-analysis in Diabetic Medicine pooled 6 randomized trials and 587 men with type 2 diabetes and found improved sexual desire (pooled effect size 0.314, 95% CI 0.082 to 0.546) and erectile function (0.203, 95% CI 0.007 to 0.399). Corona 2017 independently reported that the erectile benefit was smaller in men with diabetes and obesity.

Algeffari’s authors report no significant effect on constitutional symptoms or other sexual domains, and state that long-term risks in this group are unknown. The related metabolic evidence is set out in testosterone, blood sugar and metabolic health.

Where did the 12 nmol/L threshold come from?

It comes from the older meta-analytic literature. Isidori’s 2005 meta-analysis in Clinical Endocrinology covered 17 randomized placebo-controlled trials and 656 subjects, and found that in men with a baseline testosterone below 12 nmol/L, treatment moderately improved nocturnal erections, sexual thoughts and motivation, successful intercourse, erectile function scores and overall sexual satisfaction.

The same paper found no effect in eugonadal men, that is, men whose testosterone was already normal, and reported that the effect declines over time and shrinks as baseline testosterone rises. That threshold is still the one the European Association of Urology uses today.

What do guidelines say about testosterone for mild erectile dysfunction?

The European Association of Urology guideline on sexual and reproductive health, 2026 edition with a limited update in March 2026, states: “Use testosterone therapy as first-line treatment in hypogonadal patients with mild erectile dysfunction.” The same chapter makes a strong recommendation to use a total testosterone of 12 nmol/L (3.5 ng/mL) as the diagnostic threshold for late-onset hypogonadism, measured fasting between 07:00 and 10:00 and confirmed on two separate occasions.

The wording is specific. The recommendation is for hypogonadal patients, not for men with erectile dysfunction in general. The European Academy of Andrology guidelines on functional hypogonadism in males, published in 2020, go further and put lifestyle modification and weight reduction before testosterone when the hypogonadism is functional rather than organic, and require organic causes to be excluded first.

Who does this evidence apply to?

It applies to men with confirmed low testosterone, and it does not apply to men with normal testosterone levels. Health Canada’s product monograph for oral testosterone undecanoate capsules, authorized 12 December 2025, requires deficiency to be “clearly demonstrated by clinical features and confirmed by two separate validated biochemical assays (morning testosterone)” before treatment starts, and states that the product should not be used “to treat non-specific symptoms suggestive of hypogonadism if testosterone deficiency has not been demonstrated.” What testing your own case needs is a decision for your doctor or nurse practitioner.

Health Canada’s Information Update of 15 July 2014 says the same thing in plainer language: testosterone products “should not be used in men for non-specific symptoms if laboratory tests have not been done to confirm a low testosterone level and other possible causes for the symptoms have not been excluded.” How that diagnosis is made in Canada is covered in how low testosterone is diagnosed.

What the evidence does not show

Testosterone is not a treatment for erectile dysfunction in men whose testosterone is normal. Isidori 2005 found no effect in eugonadal men across 17 randomized placebo-controlled trials and 656 subjects, and reported that the benefit shrinks as baseline testosterone rises.

Not every analysis finds an erectile benefit even in men with low testosterone. Li’s 2020 meta-analysis in the International Journal of Endocrinology, covering 18 randomized trials and 1,415 patients (767 treated, 648 control) with type 2 diabetes or metabolic syndrome, found that erectile function measured by the IIEF-5 did not improve, while Aging Males’ Symptoms scores did. The TRAVERSE substudy (Pencina 2024) likewise found no erectile function improvement versus placebo.

The older breadth citation comes with a warning attached. Corona’s 2014 meta-analysis in the Journal of Sexual Medicine covered 41 randomized trials (29 comparing testosterone with placebo, 12 adding testosterone to a PDE5 inhibitor) and found significant improvement in erectile function and libido that survived a trim-and-fill correction for publication bias (95% CI 0.04 to 0.53 and 0.12 to 0.52). The authors also state that publication bias was detected, that the positive effect retained significance only in trials that were partly or wholly industry-supported, and that many of the trials mixed men with normal and low testosterone.

Two further null findings belong here. Cunningham 2016 found that no threshold testosterone level and none of 27 baseline characteristics predicted who would respond. Hudson 2023 found no significant improvement on the Beck Depression Inventory, which is discussed further in testosterone, energy and mood. Algeffari 2018 found no significant effect on constitutional symptoms or other sexual domains in men with type 2 diabetes, and states that long-term risks in that group are unknown.

Frequently asked questions

Does testosterone therapy improve erections?

In men with confirmed low testosterone, yes, on average. Corona’s 2017 meta-analysis in European Urology pooled 14 placebo-controlled trials and 2,298 men and found a mean difference of 2.31 (95% CI 1.41 to 3.22) on the IIEF erectile function domain. The improvement is real but modest, and it is an average across groups rather than a promise for any one person.

Does testosterone treat erectile dysfunction in men with normal testosterone?

No. Isidori’s 2005 meta-analysis in Clinical Endocrinology, covering 17 randomized placebo-controlled trials and 656 men, found improvement only below 12 nmol/L and no effect in men with normal levels, with the effect shrinking as baseline testosterone rose. Testosterone is authorized in Canada for confirmed deficiency, not as a treatment for erectile dysfunction on its own.

Why did the TRAVERSE substudy not show an erectile function benefit?

The TRAVERSE sexual function substudy (Pencina 2024, Journal of Clinical Endocrinology and Metabolism) enrolled 1,161 men selected for low libido rather than for erectile dysfunction. Sexual activity improved by 0.49 acts per day more than placebo at 6 months (95% CI 0.19 to 0.79), and hypogonadal symptoms and sexual desire improved, but erectile function specifically did not improve versus placebo.

Does testosterone help men with type 2 diabetes and sexual dysfunction?

Modestly. Algeffari’s 2018 meta-analysis in Diabetic Medicine pooled 6 randomized trials and 587 men with type 2 diabetes and found improved sexual desire (pooled effect size 0.314, 95% CI 0.082 to 0.546) and erectile function (0.203, 95% CI 0.007 to 0.399). The authors report no significant effect on constitutional symptoms or other sexual domains, and say long-term risks in this group are unknown.

What testosterone level is considered low?

The European Association of Urology guideline, 2026 edition with a limited update in March 2026, makes a strong recommendation to use a total testosterone of 12 nmol/L (3.5 ng/mL) as the diagnostic threshold for late-onset hypogonadism, measured fasting between 07:00 and 10:00 and confirmed on two separate occasions. Health Canada’s product monograph for oral testosterone undecanoate, authorized 12 December 2025, requires confirmation by two separate validated morning assays.

References

1. Corona G, et al. 2017. Meta-analysis of Results of Testosterone Therapy on Sexual Function Based on International Index of Erectile Function Scores. European Urology. PMID 28434676. DOI: https://doi.org/10.1016/j.eururo.2017.03.032
2. Hudson J, et al. 2023. Symptomatic benefits of testosterone treatment in patient subgroups: a systematic review, individual participant data meta-analysis, and aggregate data meta-analysis. Lancet Healthy Longevity. PMID 37804846. DOI: https://doi.org/10.1016/S2666-7568(23)00169-1
3. Pencina KM, et al. 2024. Effect of Testosterone Replacement Therapy on Sexual Function and Hypogonadal Symptoms in Men with Hypogonadism. Journal of Clinical Endocrinology and Metabolism. PMID 37589949. DOI: https://doi.org/10.1210/clinem/dgad484
4. Snyder PJ, et al. 2016. Effects of Testosterone Treatment in Older Men. New England Journal of Medicine. PMID 26886521. DOI: https://doi.org/10.1056/NEJMoa1506119
5. Cunningham GR, et al. 2016. Testosterone Treatment and Sexual Function in Older Men With Low Testosterone Levels. Journal of Clinical Endocrinology and Metabolism. PMID 27355400. DOI: https://doi.org/10.1210/jc.2016-1645
6. Corona G, et al. 2014. Testosterone supplementation and sexual function: a meta-analysis study. Journal of Sexual Medicine. PMID 24697970. DOI: https://doi.org/10.1111/jsm.12536
7. Algeffari M, et al. 2018. Testosterone therapy for sexual dysfunction in men with Type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials. Diabetic Medicine. PMID 29171080. DOI: https://doi.org/10.1111/dme.13553
8. Isidori AM, et al. 2005. Effects of testosterone on sexual function in men: results of a meta-analysis. Clinical Endocrinology. PMID 16181230. DOI: https://doi.org/10.1111/j.1365-2265.2005.02350.x
9. Li SY, et al. 2020. Metabolic Effects of Testosterone Replacement Therapy in Patients with Type 2 Diabetes Mellitus or Metabolic Syndrome: A Meta-Analysis. International Journal of Endocrinology. PMID 33061966. DOI: https://doi.org/10.1155/2020/4732021
10. Bhasin S, et al. 2018. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism. PMID 29562364. DOI: https://doi.org/10.1210/jc.2018-00229
11. European Academy of Andrology. Guidelines on investigation, treatment and monitoring of functional hypogonadism in males. Andrology 2020;8(5):970-987. DOI: https://doi.org/10.1111/andr.12770
12. European Association of Urology. Guidelines on Sexual and Reproductive Health, male hypogonadism chapter. 2026 edition, limited update March 2026. https://uroweb.org/guidelines/sexual-and-reproductive-health/chapter/male-hypogonadism
13. Health Canada. Product monograph, oral testosterone undecanoate capsules. Authorized 12 December 2025. https://pdf.hres.ca/dpd_pm/00082762.PDF
14. Health Canada. Information Update, Possible cardiovascular problems associated with testosterone products. 15 July 2014. https://recalls-rappels.canada.ca/en/alert-recall/information-update-possible-cardiovascular-problems-associated-testosterone-products

This page is educational information, not medical advice. Testosterone is a prescription medication and a controlled substance in Canada. Talk to your doctor or pharmacist about your own situation.