Last Updated on 14 May 2026

What Is Testosterone Replacement Therapy?

Written by Jessica Lewis | PharmD, MS

Medical Affairs Specialist · Medical Writer · Medical Communications

Written by Jessica Lewis | PharmD, MS

Medical Affairs Specialist · Medical Writer · Medical Communications

See Full Bio

Testosterone replacement therapy (TRT) is a medically prescribed treatment that restores testosterone levels in adults with clinically diagnosed hypogonadism, a condition in which the body does not produce enough of the hormone. It may be appropriate for individuals with confirmed low testosterone accompanied by symptoms such as fatigue, low libido, or loss of muscle mass, but diagnosis requires laboratory testing and a full medical evaluation, not symptoms alone. A qualified healthcare provider is the essential first step for anyone considering this treatment.

At a Glance

  • What it is: A medically prescribed hormone therapy for clinically diagnosed low testosterone (hypogonadism)
  • Who it is for: Individuals with confirmed hypogonadism and clinical symptoms, not for general wellness or performance enhancement
  • How it is given: Multiple delivery methods are available, including injections, gels, patches, oral capsules, and implanted pellets
  • Key risks: Fertility impact, the need for cardiovascular monitoring, elevated red blood cell count (polycythemia), dependency on external testosterone, and the requirement for ongoing blood work
  • Monitoring: Laboratory testing at regular intervals is required throughout treatment
  • Key misconception: TRT is not a supplement, a performance enhancer, or an anti-aging treatment

What Is Testosterone Replacement Therapy?

Testosterone replacement therapy (TRT) is a prescribed medical treatment that supplies exogenous testosterone to raise serum levels in people whose bodies do not produce enough on their own. Testosterone is the primary male sex hormone and plays critical roles in sexual development, the maintenance of muscle mass and bone density, red blood cell production, mood regulation, and energy levels.

TRT is not a dietary supplement, a performance-enhancing drug, or an anti-aging remedy. The U.S. Food and Drug Administration has approved testosterone products only for the treatment of diagnosed hypogonadism, not for age-related testosterone decline in otherwise healthy individuals.1

Definition: Testosterone replacement therapy (TRT) is a physician-prescribed treatment that uses exogenous testosterone, delivered via injection, gel, patch, pellet, or other method, to restore serum testosterone levels in people with clinically diagnosed hypogonadism, a condition where the body fails to produce adequate amounts of the hormone.

What Causes Low Testosterone?

Low testosterone has two broad categories. Primary hypogonadism originates from problems within the testes themselves, while secondary hypogonadism stems from dysfunction in the hypothalamus or pituitary gland, the brain structures that signal the testes to produce testosterone.

Common causes of primary hypogonadism include testicular injury, chemotherapy or radiation therapy, and genetic conditions such as Klinefelter syndrome. Secondary hypogonadism may result from pituitary disorders, tumors, obesity, chronic illness, opioid use, or certain medications. 2

Testosterone also declines naturally with age, dropping roughly 1% per year after age 30.3 This gradual decline alone does not constitute hypogonadism. The FDA has maintained that age-related testosterone reduction, sometimes marketed as “low T,” is not an approved indication for testosterone therapy.

Signs and Symptoms of Low Testosterone

The clinical presentation of low testosterone can include2:

  • Reduced libido and sexual desire
  • Erectile dysfunction
  • Persistent fatigue and reduced energy
  • Loss of muscle mass and strength
  • Increased body fat, particularly visceral fat
  • Mood changes, irritability, or depression
  • Difficulty concentrating or mental fog
  • Reduced bone mineral density

Many symptoms of low testosterone can also happen with other health conditions, such as thyroid problems, depression, sleep apnea, or metabolic disorders. Symptoms alone are not enough to diagnose low testosterone. Blood tests are needed to confirm whether testosterone levels are low and to check for other possible causes.

How Is Low Testosterone Diagnosed?

Diagnosing low testosterone requires both symptoms of testosterone deficiency and blood tests showing testosterone levels are low. One blood test alone is not enough.

Testosterone levels naturally change throughout the day and are usually highest in the morning, so testing is typically done between 7:00 and 10:00 AM. To confirm a diagnosis, providers usually require at least two separate morning blood tests on different days.

A total testosterone level below 300 ng/dL is commonly used as part of the diagnostic criteria.4 Additional lab tests may also be ordered to look for the underlying cause and establish baseline health before treatment. These may include free testosterone, pituitary hormone testing, prostate-specific antigen (PSA), hematocrit, and liver function tests.

A full medical history and physical exam are also important. Diagnosing low testosterone is not based on lab results alone. It requires evaluating symptoms, test results, and overall health together.

Who Is TRT Appropriate For and Who Should Avoid It?

Testosterone replacement therapy may be an option for adults who have symptoms of low testosterone and blood tests confirming their levels are low. A healthcare provider should fully evaluate someone before treatment is started.

TRT is not recommended for people whose testosterone levels are normal or for those using it only for bodybuilding, athletic performance, or anti-aging purposes.

Those who should not use TRT include those with certain cancers, untreated sleep apnea, severe heart failure, very high red blood cell counts, or those trying to have children.2

If testosterone levels are only slightly low or symptoms are mild, providers may recommend lifestyle changes first, such as improving sleep, losing weight, exercising, or treating other health issues that could be contributing to symptoms.

What Happens If Low Testosterone Goes Untreated?

Low testosterone that goes untreated may affect several areas of health over time.

It has been linked to weaker bones and a higher risk of fractures, as well as loss of muscle mass and increased body fat. Low testosterone is also associated with metabolic health issues such as insulin resistance, metabolic syndrome, and a higher risk of type 2 diabetes.2 Some studies have also found links between low testosterone and changes in heart health markers.

Sexual symptoms may worsen over time, including lower sex drive and increasing erectile difficulties. Some people with low testosterone also report mood changes, low motivation, or trouble with concentration, though clinical guidelines note these symptoms overlap with conditions such as depression, sleep disorders, and thyroid dysfunction.2

Not everyone with low testosterone will experience these problems, and having these associations does not automatically mean treatment is necessary. A healthcare provider can help determine whether treatment is appropriate based on the full clinical picture.

How Does Testosterone Replacement Therapy Work?

Testosterone replacement therapy works by adding testosterone to the body to raise levels back into a normal range. Depending on the product, testosterone may be given by injection, absorbed through the skin, taken by mouth, or placed under the skin. Once absorbed, it helps restore testosterone levels throughout the body.

TRT does not correct the underlying reason testosterone is low, but rather replaces the hormone that the body is not making enough of.

An important thing to understand is that taking testosterone can reduce or shut down the body’s natural testosterone production. It can also lower sperm production, which may affect fertility. Over time, the testicles may shrink as a result.

Because of this, stopping TRT may leave some people with lower testosterone production than what they had before treatment, at least temporarily. For many people, TRT becomes a long-term treatment, so it is important to understand this before starting therapy.

Types of Testosterone Replacement Therapy

Testosterone replacement therapy comes in several forms. Each option has different pros, cons, costs, and dosing schedules.

Intramuscular (IM) Injections (Cypionate / Enanthate)

Testosterone cypionate and testosterone enanthate are injected into a large muscle, typically the gluteal or thigh muscle, every 1–2 weeks. At approximately $40–$100 per month, these are the most cost-effective options and are widely available as generics.

The main drawback is peak-and-trough fluctuations in testosterone levels, meaning energy and mood may shift between injections. IM injections may also be more likely than some other options to raise red blood cell counts2,5.

Long-Acting IM Injection (Undecanoate / AVEED®)

Testosterone undecanoate is a long-acting injection administered approximately every 10 weeks. It must be administered in a healthcare provider’s office and requires patients to stay for 30 minutes afterward due to an increased risk of pulmonary oil microembolism. Because of this risk, the long-acting IM injection has a REMS program6.

Subcutaneous Injections

Subcutaneous testosterone injections are given at home under the skin using a smaller needle, usually weekly. They tend to produce more stable testosterone levels than traditional intramuscular injections, with comparable efficacy. Cost is similar to intramuscular formulations, at about $40–$100 per month5,7.

Topical Gels and Creams

Topical testosterone gels and creams are applied daily, typically to the shoulders or upper arms. They provide relatively steady testosterone levels. Cost ranges from about $200–$600 per month, higher than injectable options.The primary safety concern is skin-to-skin transfer. Close contact with partners, children, or pets before the application site is fully dry can expose them to testosterone2,5,8.

Transdermal Patches

Testosterone patches are applied to the skin daily, usually on the back, abdomen, thigh, or upper arm. They deliver a continuous dose and cost approximately $250–$600 per month. Skin irritation at the application site is common, and patches may detach during physical activity or sweating,5,9,.

Subcutaneous Pellets (TESTOPEL®)

Testopel pellets are surgically implanted under the skin, typically in the hip area, every 3–6 months. They provide consistent testosterone release. However, once implanted, the dose cannot be adjusted. Risks include pellet extrusion and infection at the insertion site2,10.

Oral Testosterone (JATENZO®/ TLANDO®)

Oral testosterone capsules are taken twice daily with food for adequate absorption. The cost is significantly higher at about $400–$1,000+ per month.Possible side effects include gastrointestinal side effects, such as nausea. Some oral formulations may raise blood pressure, so monitoring is important5,11.

Nasal Gel (Natesto®)

Natesto is applied inside the nostrils three times daily. It avoids the risk of skin-to-skin transfer associated with topical gels. The dosing frequency can be inconvenient, and the cost is approximately $1,000 per month.Nasal irritation and rhinorrhea are possible side effects,5,12.

Buccal Tablets

Buccal testosterone tablets are placed against the upper gum twice daily, where they slowly release testosterone through the oral mucosa. They are discreet and avoid first-pass liver metabolism. Gum irritation, altered taste, and headache are among the reported side effects2,13.

Delivery Method Comparison Table

Delivery MethodFrequencyApproximate Monthly CostKey AdvantagesKey Considerations
IM Injection (Cypionate/Enanthate)Every 1–2 weeks$40–$100Most cost-effective; widely availablePeak-and-trough fluctuations; higher polycythemia risk
Long-Acting IM (AVEED)Every ~10 weeksVaries; in-office onlyLess frequent dosingREMS-required 30-min observation; in-office only
Subcutaneous InjectionUsually weekly$40–$100More stable levels; self-administeredRequires comfort with self-injection
Topical Gel/CreamDaily$200–$600Steady levels; easy applicationSkin-to-skin transfer risk; higher cost
Transdermal PatchDaily$250–$600Continuous deliverySkin irritation; may detach
Subcutaneous Pellets (TESTOPEL)Every 3–6 monthsVaries per procedureConsistent release; no daily dosingDose not adjustable once placed; minor surgical procedure
Oral Capsules (JATENZO/TLANDO)Twice daily with food$400–$1,000+No injections; oral convenienceGI effects, cardiovascular monitoring, and high cost
Nasal Gel (Natesto)Three times daily~$1,000No skin transfer riskFrequent dosing; nasal irritation; high cost
Buccal TabletTwice dailyVariesDiscreet; avoids liver first-passGum irritation, taste changes

Table references: 2,5-13

Compounded vs. FDA-Approved Testosterone

Compounded testosterone is custom-prepared by a licensed compounding pharmacy based on a healthcare provider’s prescription. These formulations may be used when a patient needs a specific dose, concentration, or delivery method that is not available in standard commercial products.

Some people choose compounded testosterone because it may be less expensive than certain brand-name options or more accessible through specific clinics and pharmacies.

Unlike commercially manufactured testosterone products, compounded medications are not FDA-approved before being dispensed. However, compounding pharmacies are regulated by state pharmacy boards, and some larger outsourcing facilities are also subject to additional federal oversight, like the FDA 503b program.14

Because compounded medications are made individually rather than mass-produced, their potency and consistency may vary more than FDA-approved products. For this reason, many clinicians prefer FDA-approved testosterone formulations when an appropriate option is available. The FDA has also issued guidance reinforcing that compounded drugs should not be used when an FDA-approved equivalent is available.15

Whether compounded testosterone is a reasonable choice depends on the individual situation, including cost, availability, and treatment goals. Patients should discuss the pros and cons with their healthcare provider.

Benefits of Testosterone Replacement Therapy

When prescribed for confirmed hypogonadism and properly monitored, TRT has been associated with a number of benefits:

  • Improved libido and sexual function
  • Increased energy and reduced fatigue
  • Improved mood, motivation, and overall sense of well-being
  • Gains in lean muscle mass and a reduction in body fat
  • Improved bone mineral density over time

Not everyone experiences significant improvement in every area, and most people describe moderate rather than dramatic changes. The degree of benefit depends on baseline hormone levels, symptom severity, overall health, and adherence to treatment and monitoring16.

What to Expect After Starting TRT: A Clinical Timeline

The following timeline reflects published data on when treatment effects typically begin to emerge. Individual experiences vary.

TimeframeExpected Changes
2–3 weeksInitial improvements in energy, mood, and sense of well-being may begin
3–6 weeksImprovements in sexual desire and erectile function often emerge
3–6 monthsChanges in body composition begin, including increased lean mass, reduced fat mass
6–12 monthsImprovements in bone mineral density become measurable; mood and cognitive effects stabilize
12+ monthsFull bone density benefits may take 2–3 years to reach maximum effect

These timeframes are approximate. Some effects appear earlier in some individuals. Providers use follow-up labs and symptom assessments to track progress and adjust dosing17.

Risks and Side Effects of Testosterone Replacement Therapy

TRT carries clinically significant risks that require informed consent and ongoing monitoring2:

  • Acne and oily skin
  • Fluid retention
  • Breast tenderness or enlargement (gynecomastia)
  • Worsening of obstructive sleep apnea
  • Elevated red blood cell count (polycythemia), which increases the risk of blood clots, stroke, or pulmonary embolism
  • Reduced sperm production, potentially leading to infertility
  • Testicular atrophy due to hypothalamic-pituitary-gonadal (HPG) axis suppression
  • Prostate-related concerns: TRT does not cause prostate cancer, but it may stimulate the growth of existing, undetected prostate cancer; PSA monitoring is required
  • Dependency on exogenous testosterone, because the body’s own production diminishes during treatment

Cardiovascular Risk and TRT: What the Evidence Shows

Cardiovascular safety has been one of the most debated aspects of testosterone therapy. 

Earlier observational studies raised concerns about increased heart attack and stroke risk, prompting the FDA to add a cardiovascular warning to testosterone product labels.

The TRAVERSE trial, published in the New England Journal of Medicine in 2023, provided the strongest evidence to date. This randomized, placebo-controlled trial enrolled approximately 5,200 men aged 45–80 with hypogonadism and a pre-existing or high risk for cardiovascular disease. The primary finding was that testosterone therapy did not increase the incidence of major adverse cardiovascular events compared with placebo.18

Based largely on TRAVERSE and subsequent review, the FDA removed the cardiovascular black box warning from testosterone product labels in early 2025.19 In December 2025, an FDA expert advisory panel convened to further review the totality of cardiovascular evidence related to testosterone therapy, reflecting the agency’s ongoing commitment to evaluating safety data as it evolves.20

This evidence is reassuring for men with diagnosed hypogonadism receiving appropriate therapy and monitoring. However, individual cardiovascular risk factors still matter, and ongoing monitoring of blood pressure, hematocrit, and lipid panels remains an important component of care.

TRT and Fertility: What Patients Need to Know

Testosterone replacement therapy suppresses the hormones that drive sperm production. Exogenous testosterone reduces the brain’s release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the signals that tell the testes to produce sperm. This can lead to significantly decreased sperm counts and, in some cases, azoospermia (the complete absence of sperm in the ejaculate).

Anyone who is currently trying to conceive or plans to in the future should discuss this with their provider before starting TRT. In many cases, fertility-sparing alternatives can be considered. Clomiphene citrate, used off-label, stimulates the body’s own testosterone and sperm production by acting on the pituitary.21 Human chorionic gonadotropin (hCG) therapy can also maintain testicular function and spermatogenesis during or in place of testosterone treatment.22

Fertility effects are generally reversible after discontinuing TRT, but recovery is not immediate. Sperm production may take several months to over a year to return to baseline levels, and full recovery is not guaranteed in every case.

Monitoring While on TRT

Ongoing laboratory monitoring is an essential part of TRT. The standard schedule involves follow-up testing at approximately 3 months after starting therapy, again at 6 months, and then every 6–12 months thereafter.

Key labs include:

  • Serum testosterone (to confirm levels are within the target range)
  • Hematocrit (to detect polycythemia)
  • PSA (prostate cancer screening marker)
  • Liver function tests
  • Lipid panel

Dose adjustments are based on the combination of lab results and symptom response, not on lab values alone. If hematocrit exceeds an acceptable threshold (typically 54%), the provider may reduce the testosterone dose, switch delivery method, or recommend therapeutic phlebotomy (blood donation) to lower red blood cell concentration2,23,24.

Can TRT Be Stopped Once Started?

TRT can be stopped, but stopping it can often cause low testosterone symptoms to return, often within weeks.

Recovery of the HPG axis is variable. Some individuals regain their pre-treatment testosterone production over weeks to months.25 Others never fully return to their prior baseline, particularly after long-duration therapy. This is sometimes referred to as the “testosterone trap,” or the concern that once started, a person may become functionally dependent on continued treatment.

This framing deserves honest discussion rather than alarm. The reality is that most people who start TRT do so because their endogenous production was already inadequate. Discontinuation decisions should always involve a healthcare provider, who can supervise a tapering strategy and monitor recovery.

How Much Does TRT Cost?

The annual cost of TRT typically ranges from $1,200–$3,600, depending on the delivery method and insurance coverage.5

Generic intramuscular injections of testosterone cypionate or enanthate are the least expensive option at approximately $40–$100 per month. Topical gels and patches generally cost $200–$600 per month.5 Oral formulations and nasal gels are the most expensive, ranging from $400 to over $1,000 per month.5

Insurance coverage varies. For FDA-approved testosterone products prescribed for diagnosed hypogonadism, many insurance plans provide partial or full coverage. TRT prescribed for age-related testosterone decline without a formal hypogonadism diagnosis is typically not covered.

Compounded testosterone is often cheaper than FDA-approved brand-name formulations, which contributes to its popularity despite the differences in regulatory oversight discussed earlier.

Telehealth TRT services have varying pricing structures. Some bundle consultation, lab work, medication, and shipping into a single monthly fee; others charge separately for each component. Patients should confirm exactly what is included before committing.

Where to Get TRT: Providers, Clinics, and Telehealth

Several types of healthcare providers prescribe TRT. Endocrinologists specialize in hormonal disorders and are well-equipped to manage complex cases, including secondary hypogonadism and pituitary conditions. Urologists often manage TRT in the context of sexual health and fertility concerns. Primary care clinicians may prescribe TRT for straightforward cases and handle routine monitoring.

Specialized men’s health clinics vary widely in the rigor of their diagnostic and monitoring practices. Some follow evidence-based protocols; others operate with a lower clinical threshold.

Telehealth platforms have significantly expanded access to TRT. Legitimate telehealth TRT care requires blood work, a complete medical history, and review by a licensed physician before any prescription is written. This is the same standard as in-person care.

Qualified care looks like this: at least two confirmatory blood tests on separate mornings, a thorough medical history, a discussion of alternatives and risks, a clear monitoring plan, and no guarantees of outcomes.

Red flags include symptom-only prescribing without lab confirmation, no requirement for repeat blood work, anti-aging or wellness framing, guaranteed results, and no discussion of fertility risks or monitoring requirements.

Frequently Asked Questions

TRT raises your testosterone levels, which can improve energy, libido, mood, muscle mass, and bone density over time. It also suppresses your body’s natural testosterone and sperm production via feedback on the HPG axis. Some effects emerge within weeks; others take months to become noticeable.

For men with diagnosed hypogonadism, current evidence suggests TRT is reasonably safe with proper monitoring. The TRAVERSE trial found no increased major cardiovascular events, and the FDA removed its cardiovascular black box warning in 2025.18,19 Long-term safety depends on regular blood work and ongoing medical supervision.

Yes. TRT suppresses the hormones (FSH and LH) that drive sperm production, which can significantly reduce your sperm count or eliminate it entirely. If you are planning to conceive, discuss fertility-sparing alternatives such as clomiphene citrate or hCG therapy with your provider before starting treatment.21,22

TRT uses testosterone prescribed at physiological doses to restore normal hormone levels in people with diagnosed hypogonadism. Anabolic steroid use involves supraphysiologic doses, often many times the normal range, typically taken without medical supervision for muscle building or performance enhancement.

Some effects, like improved energy and mood, may begin within 2–3 weeks. Sexual function improvements often emerge around 3–6 weeks, and body composition changes develop over several months.17 Your provider will track your progress through follow-up labs and symptom assessments.

Conclusion

Testosterone replacement therapy is a prescribed medical treatment for adults with clinically diagnosed hypogonadism, confirmed by laboratory testing and the presence of symptoms. When properly prescribed and monitored, it can improve energy, sexual function, mood, body composition, and bone density. Risks include fertility suppression, polycythemia, dependency on exogenous testosterone, and the need for lifelong monitoring.

TRT is not a supplement, a performance enhancer, or an anti-aging treatment. The decision to start is highly individualized and depends on confirmed diagnosis, a thorough discussion of benefits and risks, and a clear plan for ongoing monitoring. A qualified medical evaluation is the appropriate next step for anyone considering this treatment.

References

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  2. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. doi:10.1210/jc.2018-00229 
  3. Harman SM, Metter EJ, Tobin JD, Pearson J, Blackman MR; Baltimore Longitudinal Study of Aging. Longitudinal effects of aging on serum total and free testosterone levels in healthy men. Baltimore Longitudinal Study of Aging. J Clin Endocrinol Metab. 2001;86(2):724-731. 
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  7. McFarland J, Craig W, Clarke NJ, Spratt DI. Serum Testosterone Concentrations Remain Stable Between Injections in Patients Receiving Subcutaneous Testosterone. J Endocr Soc. 2017;1(8):1095-1103. 
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  10. TESTOPEL (testosterone pellets) [prescribing information]. Malvern, PA: Endo USA, Inc; 2025. 
  11. TLANDO (testosterone undecanoate) capsules, for oral use [prescribing information]. Ewing, NJ: Verity Pharmaceuticals, Inc; 2025. 
  12. Natesto (testosterone) nasal gel [prescribing information]. Toronto, ON: Acerus Pharmaceuticals Corporation; 2025. 
  13. Striant (testosterone buccal system) [prescribing information]. Livingston, NJ: Columbia Laboratories, Inc; 2011. 
  14. U.S. Food and Drug Administration. Compounding and the FDA: Questions and Answers. Updated June 2023. Accessed April 28, 2026. https://www.fda.gov/drugs/human-drug-compounding/compounding-inspections-and-oversight-frequently-asked-questions 
  15. U.S. Food and Drug Administration. Compounding and the FDA: Questions and answers. Updated July 15, 2024. Accessed April 28, 2026. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers 
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  17. Saad F, Aversa A, Isidori AM, Zafalon L, Zitzmann M, Gooren L. Onset of effects of testosterone treatment and time span until maximum effects are achieved. Eur J Endocrinol. 2011;165(5):675-685.  
  18. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107-117. 
  19. Center for Drug Evaluation and Research. FDA issues class-wide labeling changes for testosterone products. U.S. Food and Drug Administration. Published February 28, 2025. Accessed April 28, 2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fda-issues-class-wide-labeling-changes-testosterone-products
  20. Center for Drug Evaluation and Research. FDA issues class-wide labeling changes for testosterone products. U.S. Food and Drug Administration.  Published December 10, 2025. Accessed April 28, 2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fda-issues-class-wide-labeling-changes-testosterone-products
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  25. Handelsman DJ, Desai R, Conway AJ, et al. Recovery of male reproductive endocrine function after ceasing prolonged testosterone undecanoate injections. Eur J Endocrinol. 2022;186(3):307-318. Published 2022 Jan 28.