Who it actually helps
Low testosterone and erectile dysfunction overlap, but they are not the same condition and they do not respond to the same treatment. Testosterone drives sexual desire far more strongly than it drives the mechanics of an erection. That distinction explains most of the confusion in this area.
| Presentation | What usually helps |
|---|---|
| Good desire, poor erection | PDE5 inhibitor and investigation of vascular causes. Testosterone is unlikely to be the answer. |
| Low desire, low energy, poor morning erections, confirmed low testosterone | Testosterone therapy is a reasonable first step, often alongside a PDE5 inhibitor. |
| Poor response to PDE5 inhibitors plus confirmed low testosterone | Correcting testosterone can improve the response to the tablet — a well-described interaction. |
| Any symptoms with normal testosterone | Testosterone therapy is not indicated. Look elsewhere for the cause. |
Getting the diagnosis right
Testosterone follows a daily rhythm, peaking in the morning, and a single reading can be misleading. Guidelines therefore require confirmation.
- Two morning total testosterone measurements on separate days, ideally before 10am and fasting. A commonly used threshold for deficiency is around 300 ng/dL, though laboratories and guidelines differ.
- Symptoms that match — low libido, fatigue, loss of morning erections, low mood, reduced muscle mass. Numbers without symptoms do not warrant treatment.
- Follow-up tests to find the cause — LH and FSH to distinguish a testicular problem from a pituitary one, plus prolactin where indicated.
- Baseline safety bloods — haematocrit and, in men over 40 or with risk factors, PSA.
- A fertility conversation before anything is prescribed.
The available formulations
| Form | Frequency | Considerations |
|---|---|---|
| Intramuscular or subcutaneous injection | Weekly to fortnightly | Inexpensive and effective. Levels can peak and trough; more frequent smaller doses smooth this out. |
| Topical gel | Daily | Steady levels, but the drug can transfer to a partner or child through skin contact. Cover the site. |
| Skin patch | Daily | Steady levels; skin irritation is common. |
| Subcutaneous pellets | Every 3–6 months | Convenient. Requires a minor procedure and cannot be adjusted or withdrawn quickly. |
| Nasal gel | Multiple times daily | Avoids skin transfer; the dosing schedule suits few people. |
| Oral testosterone undecanoate | Twice daily with food | Newer formulations avoid the liver toxicity of older oral androgens. Blood pressure monitoring is required. |
Risks and monitoring
- Fertility suppression
- Exogenous testosterone shuts down the body's own signal to the testicles, and sperm production falls — sometimes to zero. This is the single most important consequence to understand before starting. It is usually reversible, but not always, and recovery can take many months.
- Raised haematocrit
- Testosterone stimulates red cell production. Too thick a blood count raises clotting risk, so haematocrit is checked at baseline, at 3–6 months, then annually.
- Prostate effects
- Testosterone does not appear to cause prostate cancer, but it can accelerate an existing one. PSA monitoring is standard in men over 40 or with risk factors, and untreated prostate cancer is a contraindication.
- Cardiovascular safety
- This was debated for years. The large randomised TRAVERSE trial, published in 2023, did not find an increase in major adverse cardiac events among men with hypogonadism and elevated cardiovascular risk. Some formulations still carry blood-pressure warnings, and monitoring remains appropriate.
- Sleep apnoea
- Testosterone can worsen existing obstructive sleep apnoea. If you snore heavily or wake unrefreshed, get assessed first — see sleep apnoea and ED.
FAQ
Frequently asked questions
Will testosterone fix my ED?
Only if low testosterone is contributing to it. In men with normal levels it does not improve erections, and it carries real risks. Confirm the diagnosis before treating it.
How long before I notice anything?
Libido and mood often respond within three to six weeks. Erectile function, if it responds at all, can take up to six months.
Can I take testosterone and Viagra together?
Yes, and in hypogonadal men the combination often works better than either alone. Both should be prescribed and monitored by the same clinician.
Is it lifelong?
Usually, if the cause is permanent. Stopping returns you to your untreated baseline — and after suppression, sometimes temporarily below it.
Do over-the-counter testosterone boosters work?
There is no good evidence that supplement 'boosters' raise testosterone meaningfully or improve erections. See our review of ED supplements.
Sources
What this is based on
We link to primary sources — clinical guidelines, regulator publications and peer-reviewed research — wherever possible. Links open on third-party sites we do not control.
- [01]American Urological Association. Testosterone Deficiency: AUA Guideline (2018).
- [02]Endocrine Society. Testosterone Therapy in Men With Hypogonadism — clinical practice guideline (2018).
- [03]U.S. Food and Drug Administration. Drugs@FDA — approved drug products and prescribing information.
- [04]National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for Erectile Dysfunction.