For men with confirmed, symptomatic hypogonadism, testosterone replacement therapy can restore energy, sexual function, mood, and lean mass in the majority of patients within months. It is also a treatment that has been marketed too aggressively, prescribed too casually, and clouded by a long-running controversy over cardiovascular safety. The 2023 publication of the TRAVERSE trial in the New England Journal of Medicine and a 2025 update to FDA labeling substantially changed that conversation. Understanding who TRT is actually for, which formulations exist, what the monitoring looks like, and what the therapy does — and does not do — matters before starting treatment that, for many men, becomes lifelong. This article is general education, not medical advice, and is not a substitute for care from a qualified clinician.
How TRT Works and Who It Is For
TRT supplies testosterone from outside the body to bring serum levels back into a healthy range for men. It is important to be clear about who the treatment is meant for. The FDA states that testosterone products are approved only for men who have low testosterone together with an associated medical condition — for example, testicular failure, or a disorder of the pituitary gland or hypothalamus. Testosterone is not FDA-approved for the low levels that can accompany normal aging without an underlying medical cause, and it is not a treatment for “low energy,” “low motivation,” or general midlife fatigue on their own.
Guideline bodies set a similarly cautious bar. The Endocrine Society recommends TRT only in men who have symptoms of hypogonadism plus two separate morning total-testosterone measurements that are unequivocally low. The American Urological Association (AUA) uses a similar framework, confirming the diagnosis with repeat morning testing before treatment rather than acting on a single result or on symptoms alone. Morning testing matters because testosterone follows a daily rhythm and is highest earlier in the day; the exact reference thresholds vary between labs and guidelines, which is one reason interpretation belongs with a clinician rather than a self-ordered test kit. For the underlying condition, see our hypogonadism guide and, for age-related symptoms specifically, our andropause guide.
For men with reversible causes — obesity, poorly controlled diabetes, sleep apnea, thyroid disease, or opioid-induced suppression — addressing the underlying cause is the first step, and testosterone can sometimes recover on its own. TRT is generally reserved for men whose deficiency persists or whose symptoms are severe enough to warrant treatment while the underlying issue is managed. Importantly, TRT suppresses sperm production and is generally avoided in men who are actively trying to conceive; fertility-preserving alternatives such as clomiphene or hCG are used instead in that situation, under specialist care.
TRT Formulations
Multiple delivery routes are FDA-approved, each with trade-offs. The right choice — and the specific amount and schedule — is made with a prescriber; the descriptions below are for orientation only and deliberately do not include copy-able doses.
Injections
Testosterone cypionate and enanthate are given by intramuscular or subcutaneous injection on a schedule set by the prescriber, commonly every one to two weeks. They are usually the least expensive option and produce reliable serum levels, but the peaks and troughs between doses can cause some men to notice swings in mood or energy; more frequent, lower-volume injections tend to smooth that curve. Testosterone undecanoate (Aveed) is a long-acting injectable given at longer intervals, but it is only available through a restricted FDA REMS program and requires in-office administration with a 30-minute observation period, because of a rare risk of serious breathing problems and allergic reactions immediately after injection.
Topical Gels and Solutions
AndroGel, Testim, Fortesta, and Axiron are applied daily to the skin. They produce steady levels and are convenient, but they carry a boxed warning about secondary exposure: testosterone can transfer through skin-to-skin contact to women and children, where it can cause harm, including inappropriate virilization in children. Careful application, covering the area, and washing hands are essential, and these products should be kept away from partners, children, and pets. Brand-name gels are considerably more expensive than generic versions, and insurance often requires trying a cheaper alternative first.
Pellets
Testopel implants are placed under the skin in the office and release testosterone over several months. They produce steady levels and avoid daily application, but placement is a minor in-office procedure and the pellets cannot be removed easily if the dose needs adjusting. Costs are typically billed per insertion and are often partially covered by insurance.
Oral and Nasal
Newer oral testosterone undecanoate capsules (Jatenzo, Tlando, Kyzatrex) are taken with food and are designed to avoid the liver toxicity linked to older oral preparations such as methyltestosterone. They tend to be expensive and coverage is variable. Natesto is a nasal gel; its short action produces a more natural daily pattern, but it must be used several times a day, which some men find inconvenient. As above, the exact amount and frequency for any of these is set by the prescriber.
What TRT Realistically Does
Based on the multicenter Testosterone Trials and the TRAVERSE trial, men with genuine hypogonadism can generally expect the following, with a good deal of individual variation:
Sexual function: Improvement in libido and, for some men, erectile function — particularly when low testosterone was a driver. Men with vascular erectile dysfunction and normal testosterone are unlikely to benefit from testosterone alone. See our erectile dysfunction guide for the fuller picture on ED treatment.
Body composition: Modest gains in lean mass and reductions in fat mass over roughly 6 to 12 months, with measurable improvement in bone mineral density. Strength gains are modest unless paired with resistance training.
Mood and energy: Improvement in mood, energy, and sense of well-being is commonly reported but variable. Testosterone is not a treatment for clinical depression, which needs its own evaluation and care.
Cognition: Effects on memory and thinking have been inconsistent in trials. TRT should not be prescribed primarily for cognitive complaints in men who do not have biochemically confirmed hypogonadism.
Side Effects and Monitoring
The side effects worth knowing about — covered in more depth in our TRT side effects and risks guide — include a rise in red-blood-cell count (erythrocytosis or polycythemia), suppression of sperm production and reduced fertility, acne and oily skin, breast tissue enlargement (gynecomastia), worsening of obstructive sleep apnea, prostate-related concerns such as PSA changes and urinary symptoms, fluid retention, and increases in blood pressure. MedlinePlus notes that testosterone can cause blood clots, so new leg pain, swelling, warmth, or redness should prompt urgent evaluation. A markedly elevated red-cell count may require the prescriber to reduce the dose or, occasionally, arrange a blood draw (phlebotomy).
Monitoring is a core part of safe therapy. In line with Endocrine Society guidance, clinicians typically re-check the testosterone level, red-cell count (hematocrit), PSA, and blood pressure after starting or changing therapy and then at regular intervals, with prostate assessment and bone-density testing considered based on age and risk. The specific tests and intervals are individualized. If you are on TRT and have not had bloodwork in a while, that is a reason to see your prescriber — not to adjust anything yourself.
Cardiovascular Safety and the 2025 Label Change
For over a decade, conflicting observational data created uncertainty about whether TRT raised cardiovascular risk. The TRAVERSE trial — a randomized, placebo-controlled study of more than 5,000 middle-aged and older men with hypogonadism and high cardiovascular risk, published in 2023 — provided the clearest answer to date. As the FDA summarizes, it found no meaningful difference in serious cardiovascular events between men treated with a testosterone gel and those given placebo (about 7.0% versus 7.3%), and the agency concluded the trial did not show a new cardiovascular safety signal. The trial did note modestly higher rates of some events, including atrial fibrillation and pulmonary embolism.
On the strength of that evidence, the FDA required a class-wide labeling change for testosterone products in 2025. Per the FDA, that update removed the earlier boxed warning about possible cardiovascular risk that had been in place since the 2010s and added a new warning that testosterone can increase blood pressure, which can raise the risk of heart attack and stroke. The cardiovascular-event scare that dominated TRT discussions in the 2010s has been substantially defused, but the therapy is not risk-free, and blood pressure is now something prescribers are directed to watch. Because drug labeling continues to evolve, verify the current labeling for your specific product with your prescriber or on the FDA website.
When to seek emergency care: Call 911 or go to the nearest emergency room if, while on TRT, you have chest pain, severe shortness of breath, sudden one-sided weakness or numbness, trouble speaking, or a swollen, painful leg — these can signal a heart attack, pulmonary embolism, stroke, or a blood clot in the leg.
Testosterone Is a Controlled Substance: Do Not Self-Source or Self-Dose
Testosterone is a Schedule III controlled substance in the United States. That has real consequences for how it should — and should not — be obtained and used. Do not buy testosterone from online “research chemical” vendors, overseas pharmacies, gyms, or bulk suppliers, and do not use leftover vials, a friend’s prescription, or bodybuilding-forum protocols. Products from unregulated sources may be counterfeit, contaminated, or wrongly dosed, and supraphysiologic “cycles” of the kind used for physique enhancement carry serious risks including dangerous rises in red-cell count, blood clots, high blood pressure, testicular shrinkage, and long-term or permanent infertility.
For the same reasons, this guide does not provide milligram amounts, injection volumes, or a schedule you could copy. The correct dose is individual, is set only by a prescribing clinician, and is adjusted using your symptoms and your bloodwork over time. If your current regimen does not feel right, contact your prescriber rather than changing it yourself — and never abruptly increase a dose to chase a result.
Cost and Insurance
TRT costs vary widely by formulation and pharmacy, and the figures below are rough estimates that change over time — verify current pricing with your pharmacy or plan. Generic injectable testosterone is generally the least expensive option; generic gels cost more, and brand-name gels, pellets, and oral products cost more still. Most commercial plans cover injectable and generic gel formulations when biochemical hypogonadism is documented; brand-name gels and oral testosterone often require prior authorization, and Medicare Part D coverage varies by plan. Self-pay clinics frequently bundle injectable testosterone with monitoring for a monthly fee. Because prices and coverage shift, treat any quote as a starting point. For broader context, see our healthcare costs guide.
Who TRT Is Right For
The appropriate TRT candidate has biochemically confirmed hypogonadism on two morning tests, has clinical symptoms, is not actively trying to conceive, has had reversible causes addressed, and has discussed cardiovascular, blood-pressure, and prostate considerations with a clinician. Men with active prostate or breast cancer, untreated severe sleep apnea, significant lower urinary tract symptoms, a very high red-cell count, or uncontrolled heart failure generally are not candidates without further evaluation. For related conditions, see our hypogonadism and andropause guides and the medical conditions hub.
Frequently Asked Questions
How long until TRT starts working?
Sexual symptoms often begin to improve within the first several weeks. Energy and mood improvements commonly appear over the first few months. Changes in body composition take roughly 6 to 12 months, and bone-density changes take longer still. Men who do not feel better after several months of well-monitored therapy may have non-hormonal contributors to their symptoms and should be reassessed rather than simply given more testosterone.
Is TRT a lifelong commitment?
For men with primary hypogonadism (testicular failure), it usually is — stopping means returning to the deficient state. Men with functional hypogonadism whose underlying cause has been corrected (for example, substantial weight loss or treated sleep apnea) may be able to come off therapy. Any discontinuation should be gradual and supervised by the prescriber.
Will TRT make me infertile?
Usually, yes, while you are on it. Testosterone from outside the body signals the brain to stop the hormones that drive sperm production, halting it in most men over a few months. Sperm production often recovers after stopping, but recovery can take many months to a couple of years and is not guaranteed. Men who want to preserve fertility should discuss clomiphene or hCG with a specialist, or bank sperm before starting.
Can I get TRT through a telehealth clinic?
Often, yes — many US-licensed telehealth platforms offer TRT through licensed clinicians and partnered pharmacies. Quality varies considerably. Reputable platforms follow Endocrine Society or AUA guidance, require two morning testosterone measurements before prescribing, and provide ongoing lab monitoring. Be wary of any service that prescribes testosterone without lab confirmation, downplays the risks, or ships product without follow-up.
Can TRT be used just to build muscle or boost energy?
No. Testosterone is not FDA-approved for muscle building, athletic performance, or general energy, and using it that way — especially at the high doses seen in physique “cycles” — carries serious health and legal risks. If you have symptoms, the right step is evaluation for genuine hypogonadism, not self-treatment.
The Bottom Line
Testosterone replacement therapy is a valuable, well-studied treatment for men with confirmed, symptomatic hypogonadism and an associated medical cause. It is not a wellness-optimization tool for men with normal levels, and it is not a shortcut around healthy lifestyle changes when the cause is reversible. With careful diagnosis, an appropriate formulation, prescriber-directed dosing, and consistent monitoring — now including blood pressure — TRT can deliver meaningful improvements in sexual function, body composition, mood, and bone health while keeping risks manageable. A clinician familiar with current guidelines is the practical next step; a bulk vial from the internet is not.
This article is general education, not medical advice, and is not a substitute for care from a qualified clinician. Testosterone is a Schedule III controlled substance and is FDA-approved only for diagnosed low testosterone with an associated medical condition — not for normal aging or “low energy” alone. Do not self-source, bulk-buy, or self-dose testosterone, and do not use any dose you read online; all dosing must be set and adjusted by your prescriber based on your bloodwork. Drug labeling continues to change — verify current FDA labeling for your product with the FDA or your prescriber. If you have chest pain, severe shortness of breath, sudden weakness or numbness, or a swollen, painful leg while on TRT, call 911 or go to the nearest emergency room.