What Is TRT? A Plain-Language Explainer

The short version

Testosterone replacement therapy (TRT) is the medical practice of supplementing or replacing the body’s own testosterone production with prescribed testosterone, in patients diagnosed with hypogonadism — a condition where the body doesn’t produce enough testosterone on its own.

It is a chronic, ongoing treatment. It’s not a performance enhancer for men with normal levels, and the diagnostic threshold matters: in a man with normal levels, adding more testosterone isn’t medicine, it’s anabolic steroid use, with the same risks but without the medical justification.

What testosterone does

Testosterone is the dominant male sex hormone. In adult men, it’s produced primarily by the testes (about 95%) and in smaller amounts by the adrenal glands. Its functions in the body are broad:

• Maintains muscle mass and strength
• Maintains bone density
• Drives sex drive and erectile function
• Regulates red blood cell production
• Influences mood, cognition, and energy
• Supports sperm production (indirectly, through downstream signaling)

Testosterone production naturally declines with age — typically around 1–2% per year starting in the late 30s. Most men age into their 80s with testosterone levels still in the “normal” range. For some men, levels drop below the normal range and produce symptoms — that’s hypogonadism, and that’s the population for whom TRT is indicated.

Two kinds of low testosterone

Doctors distinguish two patterns of low T because they have different causes and sometimes different treatments:

Primary hypogonadism — the testes themselves can’t produce enough testosterone. Causes include genetic conditions (Klinefelter syndrome), prior testicular damage (trauma, mumps orchitis, chemotherapy, radiation), undescended testicles in childhood, or age-related testicular failure. Lab signature: low testosterone with high LH and FSH. The body is signaling the testes to make more, but the testes can’t respond.

Secondary hypogonadism — the testes are functional but aren’t being told to produce. The signal failure is in the hypothalamus or pituitary. Causes include obesity, opioid use, prior anabolic steroid use, sleep apnea, certain pituitary conditions, and stress-related suppression. Lab signature: low testosterone with low or normal LH and FSH.

The distinction matters because secondary hypogonadism is sometimes reversible (treat the obesity, the sleep apnea, the medication causing it) without committing to lifelong TRT. Primary hypogonadism usually isn’t.

How TRT is diagnosed

Proper TRT diagnosis is a multi-step process. Skipping any of these steps is a sign of a poorly run clinic.

1. Symptoms. Fatigue not explained by sleep, low libido, erectile dysfunction, mood changes, brain fog, loss of muscle, weight gain (especially abdominal), reduced morning erections, gynecomastia. Symptoms alone don’t diagnose anything — they justify a workup.
2. Morning blood draw. Total testosterone measured before 10 AM. Testosterone follows a daily rhythm with peak levels in the morning. Afternoon draws miss the peak and can produce false-low readings.
3. Confirmation. A single low value doesn’t establish the diagnosis. The standard is two confirmed low morning draws on different days, both below 300 ng/dL (the conventional threshold for hypogonadism in U.S. practice; some labs and clinicians use 264 ng/dL based on more recent reference ranges).
4. Full hormone panel. Free testosterone, SHBG, LH, FSH, estradiol, prolactin, TSH, hematocrit. This panel determines primary vs secondary hypogonadism and screens for other causes of similar symptoms.
5. Rule-out workup. Untreated thyroid disease, sleep apnea, depression, anemia, opioid use, and certain medications produce overlapping symptoms. A responsible clinician rules these out before prescribing TRT.

If the workup confirms hypogonadism with corresponding symptoms, TRT is a reasonable treatment option. If labs are borderline or normal, TRT is generally not appropriate, and treating the underlying issue (sleep, weight, medication review) is the better path.

How TRT is delivered

Several delivery methods exist; the choice depends on patient preference, clinician experience, and insurance coverage.

Injectable testosterone cypionate (or enanthate). The most common route. Administered subcutaneously or intramuscularly, typically once or twice weekly. Pros: predictable serum levels, low cost, decades of clinical experience. Cons: needles; weekly routine.

Topical cream or gel. Applied daily to the skin. Pros: no needles, smooth pharmacokinetics. Cons: must be applied without skipping; transfer risk to others through skin contact; absorption varies between patients.

Pellets. Subcutaneous insertion of long-acting pellets every 3–4 months in a brief office procedure. Pros: set-and-forget; no daily or weekly routine. Cons: in-office procedure; not easily adjustable mid-cycle; rare extrusion risk.

Patches. Less commonly used; daily application, can cause skin irritation.

Oral testosterone. Historically problematic due to liver effects with older formulations. Newer formulations (Jatenzo, Tlando) are FDA-approved with better profiles, but oral testosterone is still less common than the formats above.

What TRT does (and doesn’t) do for symptoms

Patients on properly managed TRT typically report improvement in:

• Energy and stamina
• Mood and motivation (this can take 1–3 months to fully manifest)
• Libido and erectile function
• Strength and lean body mass (especially with concurrent training)
• Sleep quality (when not complicated by sleep apnea)

What TRT does not reliably do:

• Cure depression in patients with normal-to-low testosterone. If depression is the problem, treat the depression.
• Cure erectile dysfunction in patients with normal testosterone. ED has many causes (vascular, neurological, psychological); low T is one of several.
• Produce dramatic body composition changes without training and nutrition.
• Reverse age-related decline in patients whose testosterone is genuinely in the normal range. “Optimizing” normal levels into the upper range is a wellness-clinic pitch, not an evidence-based medical treatment.

What it costs

Wide range, depending on path:

• Insurance-covered through PCP or endocrinologist: $0–$50/month for generic injectable cypionate, plus periodic lab costs. Requires documented hypogonadism diagnosis and may require prior authorization.
• Cash-pay generic injectable through pharmacy discount programs: $50–$120/month for the medication, plus lab and visit costs separately.
• Telehealth all-in: $89–$250/month for medication, supplies, video consults, and routine labs combined into a flat fee.
• In-person men’s-health clinic: $150–$400/month for similar services with in-clinic care.

What the side effects are

TRT is generally well-tolerated when properly monitored. Possible effects requiring monitoring:

• Erythrocytosis (high hematocrit). Increased red blood cell production can thicken blood. Monitored every 3–6 months; managed by dose adjustment, dosing schedule changes, or therapeutic phlebotomy.
• Estrogen elevation. Some testosterone aromatizes to estradiol. Mild elevation is normal and beneficial; significant elevation can cause symptoms (gynecomastia, water retention, mood changes). Managed by dose adjustment or, in some cases, an aromatase inhibitor.
• Suppressed sperm production. Exogenous testosterone shuts down the body’s signal to produce sperm. Usually reversible after stopping but recovery can take months and isn’t guaranteed.
• Acne and skin oiliness. Common, usually mild, often improves over time.
• Sleep apnea worsening in patients with pre-existing apnea.
• Prostate concerns. Long-debated. Modern evidence does not show TRT causes prostate cancer, but TRT can fuel growth of an existing undiagnosed cancer. PSA monitoring is standard, especially for men over 40.

A short list of contraindications: active or recently treated prostate cancer or breast cancer, untreated severe sleep apnea, hematocrit consistently >50–54%, severe untreated heart failure, active fertility goals.

Coming off TRT

Important and often glossed over: TRT is generally a long-term commitment. Exogenous testosterone suppresses your body’s own production. After months or years on TRT, the hypothalamic-pituitary-gonadal axis is suppressed, and stopping abruptly typically produces a period of very low testosterone (worse than the starting point) until the body’s own production recovers — which can take 3–12 months and isn’t guaranteed.

Patients who want to come off TRT generally need a supervised taper, often combined with hCG and/or clomiphene to restart endogenous production. This is real medical care, not something to do alone.

Alternatives worth considering first

For men with borderline labs, secondary hypogonadism, or fertility concerns, several approaches sometimes resolve symptoms without committing to TRT:

• Sleep optimization. Sleep apnea treatment specifically can dramatically raise testosterone in some men.
• Weight loss. Body fat aromatizes testosterone to estradiol; reducing fat mass often raises T.
• Strength training. Modest direct effect on testosterone, larger effect on the symptoms TRT is supposed to fix.
• Medication review. Opioids, certain antidepressants, statins, and others can suppress testosterone. Sometimes a substitution helps.
• Enclomiphene-based protocols (e.g. Maximus Tribe) for secondary hypogonadism with fertility goals.
• hCG therapy as a fertility-preserving alternative or adjunct.

A good TRT clinician will explore these before reaching for the prescription pad.

How to actually start

If you suspect you may have low testosterone:

1. Get a morning total testosterone draw, ideally before 10 AM, on two separate days.
2. If both come back low, get a full hormone panel.
3. Talk to a clinician — primary care, endocrinology, urology, or a telehealth platform — and review the workup.
4. Discuss alternatives, contraindications, and your goals (including fertility).
5. If TRT is appropriate, choose a delivery format and a service.

For the comparative overview of telehealth options, see Best Online TRT Clinics. For local-care-vs-telehealth thinking by city, see the Fort Worth, Dallas, Austin, Houston, or San Antonio reference pages.