Every guy has a friend on testosterone who feels great. Here is the conversation nobody is having.

YOUR HEALTH — Issue No. 20

Hormones After 50 — Part 2: Testosterone in Men

The conversation every man should have before starting testosterone therapy. Plain Medicine covers it plainly.

I see it several times a week.

Men of all ages — complaining of fatigue. Low energy. Decreased libido. Maybe he read something online. Maybe a friend is on testosterone and feels incredible. Maybe he just wants to know if his levels are low.

"Can I get my testosterone checked?"

It is one of the most common questions I get in family practice from my male patients. And the honest answer is more complicated than most men — and many providers — make it out to be.

What testosterone actually does — and what normal looks like

Testosterone is the primary male sex hormone — produced mainly in the testes and regulated by the brain. It drives muscle mass, bone density, red blood cell production, sex drive, mood, and energy. It peaks in the late teens to early twenties and begins a gradual decline after age 30 at approximately 1 to 2 percent per year.

By age 50, most men have lost 20 to 30 percent of their peak testosterone. By age 70, the loss may be 40 percent or more. This is not a disease. It is normal male aging.

Here is the clinical nuance that matters: a reading of 350 ng/dL means something completely different for a 28-year-old than it does for a 65-year-old. The standard lab reference range — 264 to 916 ng/dL — covers all adult men aged 18 to 99. A 28-year-old at 270 ng/dL and a 72-year-old at 270 ng/dL both fall within that range. Their clinical pictures are not the same.

This is why the number alone does not tell the story. And it is why treating the number — rather than the patient — is one of the most common mistakes in testosterone management.

What I want to know before I consider testosterone therapy

When a patient comes in asking about testosterone, here is what I need to know before the conversation goes any further.

Total testosterone and free testosterone — both matter.

Total testosterone measures all the testosterone in circulation. Free testosterone measures what is actually available to the body — unbound to proteins and biologically active. A man can have a normal total testosterone and a low free testosterone. Both numbers belong in the evaluation.

Morning testing — before 10 AM.

Testosterone follows a circadian rhythm — levels are highest in the early morning and decline throughout the day. A testosterone drawn at 3 PM can look meaningfully lower than the same man's level drawn at 7 AM. If your testosterone was checked in the afternoon and came back low — it needs to be repeated in the morning before any clinical decision is made.

History matters as much as the number.

Have you been on testosterone before? Have you ever used anabolic steroids?

This matters because exogenous testosterone — testosterone from any outside source — suppresses the body's own production. The hypothalamic-pituitary-gonadal axis shuts down when it detects testosterone coming in from outside. The longer that suppression goes on, the harder it becomes to recover natural production. Men who have used anabolic steroids or prior TRT may already have compromised natural testosterone production before they ever walk into my office.

Before you treat the number — ask why it's low.

A low testosterone level is not always the disease. Sometimes it is a clue.

Obesity, poor sleep, untreated sleep apnea, certain medications, chronic illness, and significant stress can all suppress testosterone levels. In some men, treating the underlying problem improves testosterone without testosterone replacement ever entering the picture.

That is why a low number alone should not lead directly to a prescription. The more important question is why the testosterone is low.

Is the problem coming from the testes themselves — primary hypogonadism? Is the brain not sending the appropriate signals to stimulate the testes — secondary hypogonadism? Is untreated sleep apnea suppressing testosterone? Is obesity playing a role? Are medications contributing?

These are different problems. They do not necessarily have the same solution.

Sometimes the most useful thing about a low testosterone result isn't that it tells us to prescribe testosterone. It's that it tells us to ask a better question: why is this man's testosterone low?

A thorough evaluation rules out reversible causes before testosterone therapy is considered.

The conversation about feeling better

Here is one of the more honest things I tell patients about testosterone therapy: yes, you will probably feel better. If your testosterone is raised — even to supraphysiologic levels — most men report improvements in energy, mood, and libido.

But feeling better is not the same as being better.

A 55-year-old man does not need the testosterone levels of a 24-year-old. There is a reason biology gradually reduces testosterone levels as men age. Supraphysiologic levels — levels higher than what is physiologically appropriate for a man's age — come with risks that men who feel great on TRT are not always thinking about.

The perception problem in testosterone therapy is real and I see it in my practice. A man gets on TRT, feels better than he has in years, and attributes everything good to the testosterone. His provider, seeing a happy patient, continues the prescription. The CBC that should be checked every three to six months gets missed. The hematocrit climbs quietly. And then something happens.

The risks that are not in the marketing

Polycythemia — the most consistently documented risk:

Testosterone stimulates red blood cell production — erythropoiesis. This is one of the reasons men on TRT often feel more energetic. It is also one of the most dangerous consequences of unmonitored therapy.

When hematocrit rises above normal thresholds, blood viscosity increases significantly. Thicker blood moves more slowly through vessels and is more prone to clotting. Men who develop polycythemia on TRT have a significantly higher risk of heart attack, stroke, deep vein thrombosis, and pulmonary embolism.

I have seen this in my own patients. A man on testosterone replacement therapy whose hematocrit climbs quietly because nobody is checking the labs regularly. This is not a theoretical risk. It is a clinical reality.

If you are receiving testosterone from any provider — clinic, telehealth, or otherwise — and nobody is ordering regular blood work, that is a problem. You need a CBC checked regularly.

Atrial fibrillation:

The TRAVERSE trial — the landmark 2023 study of 5,246 men on testosterone replacement — found no increased risk of major adverse cardiovascular events overall. That was reassuring news for a therapy that had carried a cardiovascular warning for years.

But the TRAVERSE trial also found something that was not expected: 91 cases of atrial fibrillation in the testosterone group versus 63 in the placebo group. That difference was statistically significant. A 2025 meta-analysis of 41 trials found a more than 50% increase in arrhythmia risk in men aged 40 and older on testosterone compared to placebo.

This does not mean testosterone causes Afib in every man. It means men with existing risk factors for Afib — and men who develop palpitations or irregular heartbeat on TRT — deserve a clinical conversation about whether testosterone is contributing.

I have seen Afib develop in patients on TRT. The connection is not always made.

Fertility:

I will not prescribe testosterone to a man who still plans to have children. Exogenous testosterone suppresses the body's own production of both testosterone and sperm — often significantly. This is not a minor side effect. Secondary infertility from testosterone therapy is a real clinical problem, and it is not always reversible.

Men who want biological children in the future and who are considering testosterone therapy need to understand this clearly before starting. The conversation about fertility is not optional — it belongs at the beginning of the TRT discussion, not after the fact.

If fertility is a current or future priority — testosterone replacement therapy may not be the right intervention. There are other approaches to addressing low testosterone in this setting that preserve fertility — including medications such as clomiphene and enclomiphene that stimulate the body's own testosterone production rather than replacing it from outside. Ask your provider about these options.

Permanent suppression:

The longer a man is on exogenous testosterone, the more the body's natural production atrophies. The hypothalamic-pituitary-gonadal axis can take months to recover after stopping TRT — if it recovers fully at all. Some men who stop testosterone after years of therapy find that their natural levels never return to where they were before they started.

Getting on testosterone is a decision with long-term consequences. That is not a reason to refuse it when it is clinically appropriate. It is a reason to think carefully before starting.

The Low T industry — a plain word

The direct-to-consumer testosterone market — Low T clinics, online prescribers, subscription testosterone services — has made testosterone more accessible than at any point in history.

Accessible is not the same as appropriate.

A provider who prescribes testosterone without measuring morning total and free testosterone, without evaluating for reversible causes of symptoms, without taking a history of prior steroid or booster use, and without committing to regular CBC monitoring is not providing adequate care. Full stop.

If you are receiving testosterone therapy and your provider is not doing regular blood work — find another provider.

When testosterone therapy is appropriate

This issue is not an argument against testosterone therapy. It is an argument for testosterone therapy done correctly.

True hypogonadism — documented low testosterone on morning testing, with symptoms that meaningfully affect quality of life, after reversible causes have been ruled out — is a legitimate clinical indication for treatment. When the indication is right and the monitoring is in place, testosterone therapy can meaningfully improve a man's quality of life.

The goal is physiologic replacement — restoring testosterone to an age-appropriate level, not to the levels of a 22-year-old. The conversation with your provider should include what target level you are aiming for, how often your blood will be monitored, and what the plan is if your hematocrit rises or symptoms emerge.

Something worth saying plainly:

Every man who asks me about testosterone wants to feel better. That is a completely legitimate goal.

The question is not whether testosterone therapy works. It does — for the right patient, with the right indication, at the right dose, with the right monitoring.

The question is whether the man sitting across from me is that patient. And that takes more than a number on a lab report.

One last thought.

If your symptoms are mild — fatigue, some decrease in libido, not feeling quite like yourself — and you know your sleep isn't great, your weight has crept up, or you haven't been as active as you used to be, start there first. Those changes are harder than a prescription. But they are reversible. Testosterone therapy, as we discussed, is difficult to stop — and for some men, natural levels never fully recover after long-term use.

A prescription is easy to write. It is much harder to undo.

The Member deep-dive this week covers the five decisions that actually change the treatment conversation — formulations, SHBG and free testosterone, the prostate question answered fully, fertility-preserving alternatives including clomiphene and enclomiphene, and what the cardiovascular evidence actually shows.

Next week: Microplastics — what the 2024 New England Journal of Medicine study actually showed, and what you can do about it.

Plain Medicine is published for educational purposes only and does not constitute medical advice or establish a patient-provider relationship. Always consult your healthcare provider before making medical decisions.

— Kyle