How ED and testosterone are connected
Erections depend mostly on blood flow, nerves, and the signals that tie them to arousal. Testosterone matters for desire and for spontaneous erections, such as morning ones, and it supports the machinery, but it is not the whole story. That is why PDE5 pills can work with normal testosterone, and why a man can have low testosterone and still have normal erections.
The European Male Ageing Study (3,369 men) found that three sexual symptoms track with falling testosterone: low desire, fewer morning erections, and erectile dysfunction. Other common causes of ED, like diabetes, high blood pressure, and artery disease, can lower testosterone or coexist with low testosterone. Which symptoms actually track with low T →
When to get tested
Guidelines differ a little in emphasis, and the difference is worth understanding:
- AUA ED guideline (2018): morning total testosterone should be measured in men with ED (a moderate recommendation).
- EAU guidelines (2026): in any ED workup, evaluate labs "including glucose and lipid profile and total testosterone" (a strong recommendation). Its hypogonadism chapter adds that testing for testosterone deficiency should focus on symptomatic men and that screening questionnaires shouldn't be used.
Put together: a first ED visit should include a testosterone test as part of the standard labs, and you should push for it harder if any of these apply:
- 1Low sex drive, not just trouble with erections. A pill treats the mechanics but not desire.
- 2Fewer or no morning erections.
- 3Diabetes, metabolic syndrome, or excess weight. In the Italian study above, low testosterone was about three times as common in men with metabolic syndrome. See blood sugar and metabolic health.
- 4PDE5 pills aren't working well. The EAU notes that men with low testosterone who don't respond to PDE5 inhibitors may respond better after testosterone treatment.
- 5Other signs of low T, like fatigue, loss of muscle, or low mood. These are weaker clues on their own; see the symptoms guide.
How testing works
- Morning blood draw, when testosterone is highest. The EAU specifies between 7 and 10 a.m.
- Repeat a low result. A single low value isn't a diagnosis. The AUA calls for two early-morning measurements before diagnosing deficiency. The EAU says to repeat if the result is under 12 nmol/L (about 350 ng/dL).
- Know the cutoff your clinician uses. The AUA uses a total testosterone below 300 ng/dL together with symptoms; the EAU uses 12 nmol/L. Results near the line call for judgment and sometimes a free testosterone measurement.
- Fasting: the guidelines differ. The EAU specifies a fasting draw; the AUA's testosterone guideline does not recommend fasting. Follow your clinician's instructions.
- If it is low, the next test is LH, to see whether the problem is the testes or the brain's signal. See primary vs. secondary low T and the full bloodwork schedule.
If your ED visit didn't include a testosterone test, you can ask for one or order your own baseline; see getting tested.
If the result is low
A confirmed low result changes the plan, but not automatically toward testosterone:
- AUA: men with ED and testosterone deficiency who are considering a PDE5 inhibitor should be told that the pill may be more effective if combined with testosterone therapy (a moderate recommendation, with low-grade evidence).
- EAU: testosterone therapy is first-line for hypogonadal men with mild ED (strong), and a combination of PDE5 inhibitor and testosterone is suggested for more severe ED (weak). It cites a meta-analysis of eight randomized trials (913 men) in which the combination beat the PDE5 inhibitor alone, while noting that the specific added benefit of testosterone is unclear.
Before starting, three things deserve a conversation: whether you want children (TRT suppresses sperm), the side effects and monitoring that come with it, and whether alternatives like enclomiphene fit your type of low T. A urologist or endocrinologist can walk through these.
What the trials show
The honest picture is that testosterone helps ED when testosterone is genuinely low, and much less when it isn't.
- Men with low testosterone and symptoms. In the Testosterone Trials (790 men aged 65 and older, testosterone under 275 ng/dL), a year of testosterone gel produced significantly more sexual activity, greater desire, and better erectile function than placebo. In the sexual-function substudy (470 men with low libido), testosterone improved 10 of 12 measures of sexual activity, though increases in hormone levels tracked better with activity and desire than with erectile function specifically.
- Men without hypogonadism. A 2024 Cochrane review of 43 randomized trials (11,419 men with sexual dysfunction, excluding men with hypogonadism) concluded that short-term testosterone probably has little or no effect on erectile function versus placebo. The average improvement on the erectile function score was 2.4 points, below the 4-point difference the reviewers considered meaningful.
The takeaway: testosterone isn't an ED drug. It treats a hormone deficiency, and ED improves to the extent that the deficiency was part of the problem. Anyone selling testosterone for ED without testing first is skipping the step that decides whether it will help.
If the result is normal
That is the more common outcome, and it is useful information: it points you toward the other causes and the treatments built for them.
- Check your heart and metabolic health. ED can be an early warning sign of heart disease or diabetes. Read why, and see heart & metabolic health and blood pressure.
- Review medications, sleep, and mood. Some antidepressants and blood pressure drugs affect erections, and sleep apnea (sleep and testosterone) and depression (how they overlap with low T) are common contributors.
- Use the treatments designed for ED. PDE5 inhibitors work in most men; see the four medications compared, safety and interactions, and getting a prescription.
- If testosterone is borderline, a repeat test and a free testosterone measurement are reasonable before drawing conclusions.
Before your appointment
- Tell your clinician about desire and morning erections, not just performance.
- Ask for a morning total testosterone and, if it is low, a repeat and an LH.
- Bring your medication list, blood pressure readings, and any recent labs.
- If you are considering telehealth, ask whether they check testosterone and blood pressure before prescribing. Our TRT provider directory and review criteria show which ones do their homework.
Sources
- Burnett AL, Nehra A, Breau RH, et al. Erectile dysfunction: AUA guideline. J Urol. 2018;200:633; statements 4 and 12. American Urological Association
- Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423-432. American Urological Association
- European Association of Urology. Guidelines on sexual and reproductive health (2026): management of erectile dysfunction and male hypogonadism chapters. EAU
- Wu FC, Tajar A, Beynon JM, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. N Engl J Med. 2010;363(2):123-135. PubMed
- Corona G, Mannucci E, Schulman C, et al. Psychobiologic correlates of the metabolic syndrome and associated sexual dysfunction. Eur Urol. 2006;50(3):595-604. PubMed
- Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of testosterone treatment in older men. N Engl J Med. 2016;374(7):611-624. PubMed
- Cunningham GR, Stephens-Shields AJ, Rosen RC, et al. Testosterone treatment and sexual function in older men with low testosterone levels. J Clin Endocrinol Metab. 2016;101(8):3096-3104. PubMed
- Lee H, Hwang EC, Oh CK, et al. Testosterone replacement in men with sexual dysfunction. Cochrane Database Syst Rev. 2024;1:CD013071. PubMed