What Is TRT? Complete Guide to Testosterone Replacement Therapy (2026)

Defining TRT and Who Qualifies

Testosterone replacement therapy is the medical administration of exogenous testosterone to men whose bodies no longer produce enough on their own. The diagnosis requires both persistently low serum testosterone (below 300 ng/dL on the AUA cutoff or below 264 ng/dL per the Endocrine Society) and at least one clinical symptom such as reduced libido, erectile dysfunction, fatigue, or loss of muscle mass [1][2].

Hypogonadism falls into two categories. Primary hypogonadism originates in the testes (elevated LH and FSH with low testosterone), while secondary hypogonadism involves a failure at the hypothalamic-pituitary level (low or inappropriately normal LH/FSH with low testosterone). Both forms can qualify a patient for TRT, but the distinction matters. Secondary hypogonadism in younger men may respond to clomiphene citrate or enclomiphene, preserving fertility while raising endogenous production [4].

The AUA guidelines specify that total testosterone must be measured on at least two occasions, drawn before 10:00 AM when diurnal secretion peaks [1]. A single low reading is not sufficient. Acute illness, opioid use, and obesity can transiently suppress levels, and these reversible causes should be addressed first.

Age alone does not qualify a man for TRT. The Baltimore Longitudinal Study of Aging found that about 20% of men over 60 and 30% over 70 had testosterone below 325 ng/dL, yet many remained asymptomatic [3]. Treatment targets symptoms, not a number.

How Testosterone Declines With Age

Serum testosterone drops approximately 1 to 2% per year after age 30, according to data from the Massachusetts Male Aging Study (MMAS), which followed 1,709 men over a decade [5]. This gradual decline differs from the abrupt hormonal shift women experience during menopause. Some clinicians use the term "andropause," but the Endocrine Society avoids it because the decline is neither universal nor inevitable.

Obesity accelerates the fall. Adipose tissue expresses aromatase, which converts testosterone to estradiol. A 2012 analysis in the Journal of Clinical Endocrinology & Metabolism showed that each 1-unit increase in BMI corresponded to a 2% decrease in testosterone concentration [6]. Weight loss of 10 to 15% can raise testosterone by 100 ng/dL or more in obese men, sometimes eliminating the need for exogenous therapy entirely.

Sleep deprivation compounds the problem. Restricting young men to 5 hours of sleep per night for one week reduced daytime testosterone by 10 to 15% in a controlled University of Chicago study [7]. So can chronic stress through sustained cortisol elevation. Clinicians evaluating low testosterone should screen for sleep disorders, metabolic syndrome, and chronic opioid use before attributing the deficit to aging.

TRT Formulations Available in 2026

Clinicians choose from several delivery systems, each with distinct pharmacokinetics, cost profiles, and patient preferences. No single formulation is universally superior. The right choice depends on insurance coverage, injection comfort, and how stable the patient needs their serum levels to be.

Intramuscular injections. Testosterone cypionate and testosterone enanthate remain the most prescribed options in the United States. Typical dosing is 100 to 200 mg every 7 to 14 days. Cypionate has a half-life of approximately 8 days. Splitting the dose into twice-weekly subcutaneous injections (50 to 80 mg each) produces more stable serum concentrations and lower estradiol conversion [8].

Transdermal gels. AndroGel (1% and 1.62%) and Testim deliver 50 to 100 mg of testosterone daily through the skin. Absorption varies by application site, with the upper arms and shoulders providing the most consistent delivery. The gel must dry completely before skin contact with others, particularly women and children, due to transfer risk [9].

Testosterone pellets. Testopel involves subcutaneous implantation of 6 to 12 crystalline pellets (each 75 mg) every 3 to 6 months. A 2019 retrospective analysis in the Journal of Urology reported 84% patient satisfaction, though extrusion rates ranged from 5 to 12% depending on insertion technique [10].

Nasal testosterone. Natesto (testosterone nasal gel, 5.5 mg per nostril) is applied three times daily. It produces a pulsatile testosterone profile that more closely mimics natural diurnal rhythm. Natesto may cause less suppression of spermatogenesis than injectable formulations, making it an option for men who wish to preserve some degree of fertility [11].

Testosterone undecanoate injection (Aveed). This long-acting formulation is given as 750 mg intramuscularly every 10 weeks after an initial loading phase. It carries an FDA-mandated REMS program because of the risk of pulmonary oil microembolism and anaphylaxis, which occurred in about 1% of patients in post-marketing surveillance [12]. Administration must occur in a certified healthcare setting with a 30-minute post-injection observation period.

Benefits Documented in Clinical Trials

The Testosterone Trials (TTrials), a coordinated set of seven placebo-controlled studies enrolling 790 men aged 65 and older with testosterone below 275 ng/dL, provided the strongest evidence for TRT benefits across multiple domains [13].

Sexual function improved the most. The Sexual Function Trial showed a statistically significant increase in sexual activity and desire at 12 months (P<0.001 vs. placebo). The effect size was moderate, with treated men reporting roughly 0.6 additional sexual encounters per month [13].

Physical function saw modest gains. The Physical Function Trial found improved 6-minute walk distance, with treated men walking an additional 6.1 meters compared to placebo, though this did not reach the pre-specified clinically meaningful threshold [13].

Bone mineral density increased significantly at the lumbar spine (7.5% increase) and hip (3.2% increase) by 12 months in the Bone Trial, measured by quantitative CT [14]. Whether this translates to reduced fracture risk remains unproven.

Mood and depressive symptoms improved in men with mild depression at baseline. The Vitality Trial showed a small but statistically significant improvement in the PHQ-9 depression score [13].

Body composition changes consistently appear across TRT studies. A meta-analysis of 37 RCTs (N=2,690) published in Endocrine Reviews found that testosterone therapy increased lean body mass by an average of 3.2 kg and decreased fat mass by 1.6 kg over 12 months [15].

Dr. Shalender Bhasin, principal investigator of the TTrials and professor at Harvard Medical School, stated: "The benefits of testosterone treatment were most consistently demonstrated in sexual function, with more modest effects on physical function, vitality, and mood" [13].

Cardiovascular Safety: The TRAVERSE Trial Settles the Debate

For years, cardiovascular risk was the largest unresolved question around TRT. The TRAVERSE trial (Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men), published in the New England Journal of Medicine in 2023, enrolled 5,246 men aged 45 to 80 with hypogonadism and pre-existing or high risk of cardiovascular disease [16].

After a mean follow-up of 33 months, the primary composite outcome of major adverse cardiovascular events (death, nonfatal MI, nonfatal stroke) occurred in 7.0% of the testosterone group versus 7.3% of the placebo group (hazard ratio 0.96 to 95% CI 0.78 to 1.17). TRT did not increase cardiovascular risk [16].

This was a large, well-powered, event-driven trial. It effectively retired the cardiovascular safety signal that had emerged from two smaller, earlier studies (the TOM trial and Vigen et al. 2013 VA study), both of which had significant methodological limitations [17][18].

One finding from TRAVERSE did raise a secondary concern. The incidence of pulmonary embolism was higher in the testosterone group (0.9% vs. 0.5%), consistent with the known effect of testosterone on erythropoiesis and hematocrit elevation [16]. This reinforces the need for regular CBC monitoring.

The Endocrine Society's 2020 position, issued before TRAVERSE results, recommended against prescribing testosterone to men with recent MI or stroke within the prior 6 months [2]. The TRAVERSE data may inform future guideline revisions, though the FDA has not altered its 2015 labeling requirements for cardiovascular risk warnings.

Monitoring Protocol on TRT

Proper monitoring separates safe therapy from reckless prescribing. The AUA and Endocrine Society guidelines agree on this schedule [1][2]:

Baseline (before starting). Total testosterone (two morning draws), free testosterone, SHBG, LH, FSH, complete blood count (CBC), comprehensive metabolic panel, lipid panel, PSA, and a symptom questionnaire (ADAM or qADAM).

3 months after initiation. Total testosterone (drawn at trough for injectables), hematocrit, PSA. Assess symptom response. Adjust dose to target 450 to 600 ng/dL.

6 and 12 months. Repeat labs above plus lipid panel. Evaluate for side effects including acne, breast tenderness, mood changes, and sleep apnea symptoms.

Annually thereafter. Total testosterone, CBC, PSA, lipid panel, metabolic panel. DXA scan for men with osteoporosis risk factors at baseline.

Hematocrit is the most actionable safety lab. If it exceeds 54%, the clinician should reduce the dose, switch formulations, or recommend therapeutic phlebotomy. Testosterone increases erythropoietin production, which stimulates red blood cell formation. Polycythemia raises the risk of venous thromboembolism [1].

PSA monitoring does not require a specific threshold to trigger biopsy, but the AUA recommends referral to urology for a PSA rise greater than 1.4 ng/mL over 12 months or an absolute value exceeding 4.0 ng/mL [1]. The 2023 TRAVERSE sub-study on prostate safety found no increased incidence of prostate cancer in the testosterone group over nearly 3 years of follow-up [19].

TRT and Fertility: A Non-Negotiable Conversation

Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal (HPG) axis, reducing intratesticular testosterone to levels insufficient for spermatogenesis. Within 3 to 6 months, most men on TRT develop oligospermia or azoospermia [20]. This effect is usually reversible upon discontinuation, but recovery can take 6 to 18 months, and full recovery is not guaranteed.

The AUA explicitly states: "Testosterone therapy should not be used as a male contraceptive and should not be started in men planning fertility in the near term" [1].

For hypogonadal men who want to preserve fertility, alternatives include:

Clomiphene citrate (25 to 50 mg daily or every other day), an off-label selective estrogen receptor modulator that stimulates LH release and raises endogenous testosterone by 150 to 200 ng/dL on average [4]. Enclomiphene, its trans-isomer, received FDA attention but is not yet approved as of mid-2026.

Human chorionic gonadotropin (hCG), 1,500 to 3 to 000 IU subcutaneously two to three times per week, can be used alongside low-dose TRT to maintain intratesticular testosterone and preserve spermatogenesis [21]. However, hCG availability has been affected by regulatory changes since the FDA's 2020 enforcement of compounding restrictions under the Biologics Price Competition and Innovation Act.

Side Effects and Risk Management

The most common adverse effects of TRT, based on pooled clinical trial data, include [2][15]:

Erythrocytosis (hematocrit above 54%): occurs in 3 to 18% of patients depending on formulation and dose. Injectable testosterone produces higher peak levels and carries a greater risk than gels.

Acne and oily skin: reported by approximately 15 to 25% of patients, typically mild and manageable with topical treatments.

Testicular atrophy: occurs due to HPG axis suppression. Testicular volume may decrease by 20 to 25% within the first year.

Gynecomastia or breast tenderness: results from aromatization of testosterone to estradiol. Affects approximately 10 to 15% of men, more commonly with higher doses. An aromatase inhibitor (anastrozole 0.5 mg twice weekly) is sometimes used off-label, though the Endocrine Society recommends against routine estradiol suppression [2].

Sleep apnea: testosterone may worsen existing obstructive sleep apnea. Screen with the STOP-BANG questionnaire at baseline and follow-up.

Mood and behavioral effects are far less dramatic than popular culture suggests. The TTrials showed no increase in aggressive behavior. A minority of men report irritability or mood swings during dose adjustments.

The 2018 AUA guideline from Dr. John Mulhall and colleagues summarized the risk profile: "When properly monitored, testosterone therapy is a safe treatment for symptomatic hypogonadism, with erythrocytosis as the most common clinically significant adverse event" [1].

Cost, Insurance, and Access in 2026

Generic testosterone cypionate remains one of the most affordable hormone therapies available. A 10 mL vial of 200 mg/mL (enough for 10 to 20 weeks of treatment depending on dose) costs $30 to $80 without insurance at most pharmacies. Brand-name gels run $200 to $500 per month without coverage. Testopel pellet insertion costs $500 to $1,000 per procedure including the office visit [22].

Most commercial insurance plans cover generic injectable testosterone with a confirmed diagnosis of hypogonadism (ICD-10 E29.1) and two documented low testosterone levels. Prior authorization is commonly required for brand-name formulations.

Telehealth TRT clinics have expanded rapidly since 2020. Patients should verify that any telemedicine provider requires confirmatory lab work, uses FDA-approved medications (not research-grade peptides or gray-market products), and provides ongoing monitoring per AUA/Endocrine Society guidelines. A provider who prescribes testosterone after a single questionnaire without lab confirmation is not following evidence-based practice.

When to Stop or Adjust TRT

Not every man who starts TRT remains on it indefinitely. Reasons to discontinue or pause therapy include a desire for fertility, development of polycythemia that does not respond to dose reduction, diagnosis of hormone-sensitive cancer, or inadequate symptomatic improvement after 6 to 12 months of optimized dosing [1].

Discontinuation should be gradual when possible, with lab monitoring at 4 to 6 weeks post-cessation. Men who have been on TRT for years may experience prolonged HPG axis recovery. Some never fully recover endogenous production, particularly men over 50 who had low baseline LH prior to treatment [2].

Post-TRT recovery protocols using clomiphene or hCG are commonly employed in clinical practice, though they lack large RCT support. A 2020 retrospective cohort study of 66 men discontinuing TRT found that 90% recovered testosterone above 300 ng/dL within 12 months, but recovery was slower in men who had been on therapy for more than 3 years [23].

Patients who achieve symptom resolution and lifestyle optimization (body composition improvement, sleep restoration, stress management) during TRT may be candidates for a supervised trial off therapy, with labs rechecked at 1, 3, and 6 months to assess whether endogenous production has recovered sufficiently to maintain well-being.