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Low testosterone and erectile dysfunction

Written by David Shusterman, MD, board-certified urologist, adapted from his book ED Unlocked. General information, not medical advice for your situation. Who publishes this site.

Low testosterone can contribute to erectile dysfunction (ED), mostly by lowering desire, energy and the drive that starts an erection. But it is only one of several causes, and many men with ED have perfectly normal testosterone. Low testosterone should be diagnosed with symptoms plus two morning blood tests, not guessed at. Treating it helps when it is truly low. Taking testosterone when it is not low does not fix ED and can shut down your own production and your fertility.

How testosterone fits into erections

An erection depends on several systems working together: the brain's signal, the nerves, the blood vessels and the hormones. Testosterone sits in the hormonal part. It sets the drive, the desire that gets the whole chain started.

When testosterone is genuinely low, a typical picture is a cluster of symptoms arriving together: libido that is not just low but gone, fatigue by midday, brain fog, loss of muscle and weight gain around the middle. Erections often suffer along with desire.

But blood flow is the bigger driver of most ED. A man can have a testosterone level that is excellent and still have ED from narrowed arteries, a venous leak, nerve damage or anxiety. That is why a man who is sure his testosterone has crashed often turns out to have a different cause entirely. See what causes erectile dysfunction.

How to test testosterone properly

Testosterone is diagnosed on two things together, your symptoms and your labs. Neither one alone is enough. A proper workup looks like this:

• Test in the morning. Testosterone follows a daily rhythm and peaks in the morning. A blood draw between about 7 and 10 a.m. is the one that counts. An afternoon test can read falsely low.
• Test twice. A single reading can mislead on a bad day, so a low result should be confirmed on a separate occasion.
• Know the threshold. The widely used cutoff for true deficiency is around 300 nanograms per deciliter (ng/dL). Below that, with symptoms, there is something real to treat. Down around 200 or below, the level is low enough to act on almost regardless of symptoms.
• Check free testosterone too. Most testosterone is bound to a protein called SHBG and is not available to your tissues. A man can have a normal total level but a low free level, and still be deficient.
• Check LH and FSH. These are the signals the brain sends to the testicles. They show whether the problem is in the testicles or in the brain's orders.

Fix what may be lowering it

Some common causes of low testosterone can be improved directly:

• Excess belly fat suppresses testosterone and contains an enzyme, aromatase, that turns testosterone into estrogen. Losing as little as 5 to 10 percent of body weight can help restore hormone balance and improve sexual function.
• Poor sleep lowers testosterone. Sleep apnea, with loud snoring and pauses in breathing, can disrupt testosterone rhythms and erections. Treating it can make a real difference.
• Strength training supports testosterone, and regular exercise helps the blood vessels erections depend on.

When treatment helps, and what it costs

For a man with a measured, genuine deficiency, testosterone therapy is standard medicine. Within a few months, energy, mood, body composition and libido often improve.

But there is a warning every man should hear before starting. Your brain runs testosterone on a thermostat. When testosterone comes from outside, the brain senses plenty and stops sending LH and FSH, the signals that tell the testicles to make both testosterone and sperm. Your own production switches off, and fertility can collapse, sometimes to zero sperm.

That means you should plan as if treatment is for life. Stopping is possible, but recovery of your own production can take months to years, and during that time the low-testosterone symptoms come back in full. This applies even to men who started with a normal level.

If you want children: fertility-friendly options

If you need your testosterone raised but are not done having children, a urologist may consider approaches that protect fertility:

• Clomiphene or enclomiphene nudges the pituitary gland to send more LH and FSH, so your body makes more of its own testosterone. In men trying to preserve fertility, this approach raised testosterone by roughly 245 to 305 points at three months.
• hCG mimics LH and stimulates the testicles directly, helping preserve their size, function and sperm production. It can be used alone or alongside testosterone.
• Nasal testosterone (Natesto) is dosed three times a day and clears quickly, so it suppresses the brain's signals less than injections. Trial data show semen parameters maintained in most men, but long-term fertility data are limited and the AUA does not yet formally recommend it for men actively trying to conceive.

Sperm banking before starting testosterone is also reasonable.

Beware the "Low T" sales pitch

A whole industry promotes the idea that more testosterone is always better. Researchers posing as healthy patients have found providers willing to start men with normal hormone levels on testosterone they did not need, exposing them to side effects and risking their fertility.

Protect yourself with a few questions: Was my blood drawn in the morning, and was a low result confirmed? Were free testosterone, LH and FSH checked? Did anyone explain the effect on fertility and the likelihood of lifelong treatment? Be wary of a clinic that starts treatment the same day after a single afternoon test.

Testosterone is one piece of the ED picture, not the whole answer. Most men with ED also need attention to blood flow, and other treatments may still be needed. See ED treatment options and ED and heart health. A urologist can test you properly and explain the trade-offs. This article is general information, not medical advice for your situation.

Frequently asked questions

Can low testosterone cause erectile dysfunction?

It can contribute, mainly by lowering desire and drive. But many men with ED have normal testosterone, and blood flow problems are the more common cause.

What testosterone level is considered low?

The widely used threshold is around 300 ng/dL on a morning test, confirmed on a second test and paired with symptoms. Free testosterone should be checked as well.

Will testosterone therapy fix my ED?

If your testosterone is truly low, treatment can improve desire and sometimes erections, but many men still need other ED treatments. If your level is normal, testosterone will not help ED.

Does testosterone therapy affect fertility?

Yes. Testosterone from outside the body can shut down sperm production. Men who want children should ask about options such as clomiphene, enclomiphene or hCG.

Can I stop testosterone once I start?

Stopping is possible, but your own production may take months to years to recover, and symptoms return in the meantime. Plan as if treatment is for life.