Testosterone Replacement Therapy (TRT): What Every Man Should Know
Written by YiQiu Hu, NMD
Arizona-licensed naturopathic physician and virtual concierge medicine provider
Published August 2026 | Medically reviewed August 2026
Testosterone replacement therapy, commonly called TRT, has become increasingly visible in discussions about men's health, aging, sexual function, energy, muscle mass, and performance.
That visibility has also created considerable confusion.
TRT is sometimes marketed as a solution for fatigue, weight gain, declining motivation, reduced athletic performance, erectile dysfunction, or simply getting older. But medically appropriate testosterone therapy is more specific than that.
Testosterone replacement therapy is intended for men who have symptoms or signs consistent with testosterone deficiency together with appropriately confirmed low testosterone levels. The Endocrine Society recommends confirming low testosterone with repeat morning testing rather than diagnosing testosterone deficiency from symptoms or a single laboratory value alone.
For men who truly have testosterone deficiency, TRT may improve certain symptoms and aspects of health. For men without a clear indication, however, increasing testosterone simply because a level appears less than "optimal" may expose them to unnecessary treatment and monitoring.
Understanding what TRT can do—and what it cannot—is essential before deciding whether treatment is appropriate.
If you are still determining whether your symptoms may be related to testosterone, start with our guide to Low Testosterone in Men: Symptoms, Diagnosis, and Treatment Options.
What Is Testosterone?
Testosterone is the primary androgen, or male sex hormone. It is produced primarily by the testicles under signaling from the hypothalamus and pituitary gland.
Testosterone plays an important role in:
Sexual desire
Erectile and reproductive function
Sperm production
Muscle mass and strength
Bone health
Red blood cell production
Body composition
Development and maintenance of male secondary sexual characteristics
Testosterone levels can decline for many reasons.
Some men have primary hypogonadism, meaning the testes themselves are unable to produce adequate testosterone.
Others have secondary hypogonadism, in which signaling from the hypothalamus or pituitary gland is impaired.
The Endocrine Society recommends distinguishing these conditions using additional evaluation, including luteinizing hormone (LH) and follicle-stimulating hormone (FSH), because identifying why testosterone is low can be just as important as identifying the low level itself.
What Is Testosterone Replacement Therapy?
Testosterone replacement therapy involves providing exogenous testosterone to restore testosterone exposure in men with clinically appropriate testosterone deficiency.
Depending on the medication and the patient's needs, testosterone can be administered through:
Intramuscular or subcutaneous injections
Topical gels
Transdermal patches
Oral testosterone products
Implantable testosterone pellets
Other FDA-approved formulations
The FDA currently recognizes multiple testosterone delivery methods, including injections, topical products, patches, oral products, and buccal formulations.
Each approach has advantages and disadvantages involving convenience, cost, absorption, dosing flexibility, fluctuations in hormone levels, side effects, and monitoring.
Our detailed guide to Types of HRT: Pills, Patches, Gels, Injections, and Pellets explains these differences in greater detail.
TRT Is Not the Same as Anabolic Steroid Abuse
Medically supervised testosterone replacement and anabolic steroid abuse should not be treated as equivalent.
The purpose of TRT is generally to restore testosterone to an appropriate physiologic range in someone who has testosterone deficiency.
Anabolic steroid abuse frequently involves supraphysiologic doses of testosterone or related anabolic compounds intended to produce muscle growth or performance enhancement.
The dose, treatment goal, monitoring, and medical risks can therefore be very different.
More testosterone is not necessarily better.
The objective of appropriate TRT is not to achieve the highest testosterone number possible. Treatment should instead use the lowest appropriate dose necessary to address clinically meaningful testosterone deficiency while minimizing potential adverse effects.
Who May Be a Candidate for TRT?
The fundamental principle is straightforward:
Symptoms alone are not enough, and a low laboratory number alone is not enough.
The Endocrine Society recommends diagnosing hypogonadism only when a man has symptoms or signs consistent with testosterone deficiency along with unequivocally and consistently low testosterone concentrations. The diagnosis should generally be confirmed with a repeat morning fasting testosterone measurement.
Symptoms that may lead to evaluation include:
Reduced sexual desire
Fewer spontaneous or morning erections
Erectile dysfunction
Reduced energy
Loss of muscle mass
Increased body fat
Reduced physical performance
Depressed mood
Difficulty concentrating
Unexplained anemia
Reduced bone density
Infertility
However, many of these symptoms are nonspecific.
Fatigue, low libido, erectile dysfunction, poor concentration, or decreased motivation can also occur with:
Poor sleep
Obstructive sleep apnea
Depression
Chronic stress
Obesity
Diabetes
Thyroid disorders
Chronic illness
Excessive alcohol use
Certain medications
Nutritional deficiencies
Relationship or psychological factors
That is why appropriate testosterone evaluation involves more than ordering a testosterone level.
How Is Low Testosterone Properly Diagnosed?
A careful evaluation usually begins with symptoms, medical history, medication review, physical findings when appropriate, and laboratory testing.
Morning Testosterone Testing
Testosterone levels fluctuate during the day and are typically highest in the morning.
The Endocrine Society recommends confirming suspected testosterone deficiency by repeating a morning fasting total testosterone level when an initial level is low.
A single abnormal result should therefore rarely be viewed in isolation.
Total Testosterone vs. Free Testosterone
Total testosterone measures testosterone circulating in several forms, including testosterone bound to proteins.
Free testosterone represents the much smaller fraction that is not protein-bound.
Certain situations can alter sex hormone-binding globulin, or SHBG, potentially making total testosterone more difficult to interpret.
Depending on the clinical situation, evaluation may therefore include:
Total testosterone
Free testosterone or calculated free testosterone
SHBG
LH
FSH
Prolactin
Complete blood count
Additional endocrine or metabolic testing
Testing should be selected according to the individual rather than ordering an identical hormone panel for every man.
Why Finding the Cause Matters
Starting testosterone before understanding why testosterone is low can sometimes mask an underlying problem.
Low testosterone may be associated with conditions involving the:
Testicles
Pituitary gland
Hypothalamus
It may also occur in association with:
Obesity
Significant sleep disruption
Chronic opioid use
Certain medications
Severe illness
Excessive caloric restriction
Other endocrine abnormalities
In some circumstances, correcting an underlying contributor may improve testosterone levels without long-term replacement therapy.
Other men have permanent testosterone deficiency for which replacement therapy may be an appropriate long-term treatment.
The objective is therefore not simply to "fix the number." It is to understand the clinical situation.
What Benefits Can TRT Provide?
When testosterone deficiency has been appropriately diagnosed, treatment may improve certain symptoms.
Potential benefits can include improvement in:
Sexual Desire
Low libido is one of the more characteristic symptoms of testosterone deficiency, and appropriately selected men may experience improvement with treatment.
Sexual Function
Some men experience improvement in certain aspects of sexual function.
TRT should not, however, be viewed as a universal treatment for erectile dysfunction. Erections depend on vascular health, neurological function, medication effects, psychological factors, metabolic health, and several other systems in addition to testosterone.
Energy and Well-Being
Some men with clinically significant testosterone deficiency report improved energy or sense of well-being after treatment.
The degree of improvement varies substantially between individuals.
Muscle and Body Composition
Testosterone contributes to muscle development and maintenance.
Replacement therapy in deficient men can increase lean body mass, although TRT should not be viewed as a substitute for resistance exercise, adequate nutrition, sleep, and metabolic health.
Bone Health
Testosterone contributes to maintenance of bone density.
However, improvement in bone density does not automatically mean that testosterone should be prescribed as a general osteoporosis treatment or that TRT has been proven to prevent fractures in every patient.
Anemia
Testosterone can stimulate red blood cell production, and treatment may improve anemia in certain men with testosterone deficiency.
That same effect is also one reason blood counts must be monitored during therapy.
What TRT Should Not Be Used For
Testosterone therapy should not automatically be prescribed because someone wants to:
Lose weight
Build muscle faster
Improve athletic performance
Increase motivation
Reverse normal aging
Raise testosterone to the upper end of a laboratory range
Treat fatigue without determining its cause
The FDA continues to distinguish medically indicated treatment of testosterone deficiency from testosterone use simply for age-related decline and retains limitation-of-use language regarding age-related hypogonadism.
Men deserve treatment when treatment is medically appropriate—but they also deserve a proper evaluation rather than being placed on lifelong hormone therapy because of a vague symptom or isolated laboratory result.
What Are the Possible Side Effects of TRT?
Testosterone replacement therapy can be well tolerated when properly prescribed and monitored, but it is not risk-free.
Potential adverse effects include:
Increased hematocrit or red blood cell concentration
Acne or oily skin
Fluid retention
Changes in blood pressure
Suppression of sperm production
Testicular shrinkage
Changes in breast tissue
Changes in mood or irritability in some individuals
Worsening of certain urinary symptoms
Problems related to excessive testosterone levels
Different formulations can also have formulation-specific risks.
For example, topical testosterone can potentially transfer to another person through skin contact if application precautions are not followed.
Injections may produce greater peak-and-trough fluctuations depending on the dose and dosing schedule.
Pellets provide long-lasting treatment but are more difficult to rapidly adjust or discontinue after implantation.
TRT Can Increase Hematocrit
One of the most important laboratory effects of testosterone is stimulation of red blood cell production.
A moderate increase may be expected.
An excessive increase can cause erythrocytosis, resulting in an abnormally elevated hematocrit.
This is one reason a complete blood count and hematocrit are commonly evaluated before treatment and monitored during therapy.
If hematocrit becomes excessively elevated, the physician may need to:
Reduce the testosterone dose
Change the dosing interval
Change the testosterone formulation
Temporarily discontinue treatment
Investigate other contributing factors such as sleep apnea or smoking
Determine whether additional intervention is appropriate
TRT should never become a process of repeatedly treating an abnormal blood count while ignoring an unnecessarily high testosterone dose.
Testosterone Can Affect Blood Pressure
Cardiovascular discussions around testosterone have changed substantially over the past several years.
In February 2025, the FDA announced class-wide testosterone labeling changes after reviewing the large TRAVERSE cardiovascular outcomes trial and ambulatory blood-pressure studies.
Based on TRAVERSE, the FDA removed boxed-warning language concerning an increased risk of major adverse cardiovascular events. At the same time, ambulatory blood-pressure studies showed that testosterone products can increase blood pressure, leading the FDA to require blood-pressure warnings across testosterone products.
The practical takeaway is not that testosterone is either "good for the heart" or "bad for the heart."
Instead, cardiovascular risk should be evaluated individually, and blood pressure should remain part of appropriate monitoring.
What Did the TRAVERSE Study Find About Heart Risk?
The TRAVERSE trial was specifically designed to evaluate cardiovascular safety in middle-aged and older men with hypogonadism who had established cardiovascular disease or elevated cardiovascular risk.
The trial found that testosterone therapy was noninferior to placebo for major adverse cardiovascular events, meaning the study did not demonstrate an increased rate of the primary combined cardiovascular endpoint with testosterone therapy. This evidence contributed to the FDA's 2025 decision to remove the previous boxed-warning language about increased cardiovascular risk.
That result should not be interpreted as proof that testosterone is risk-free for every man.
Medication safety still depends on:
The patient's underlying health
Blood pressure
Testosterone dose
Hematocrit
Cardiovascular history
Sleep apnea
Other medications
Treatment formulation
Appropriate follow-up
TRT Can Significantly Reduce Fertility
This is one of the most important facts for younger men to understand.
External testosterone can suppress sperm production.
The brain normally signals the testes through LH and FSH. When testosterone is supplied from outside the body, the hypothalamus and pituitary can reduce those signals.
As a result:
Intratesticular testosterone falls
Sperm production may decrease substantially
Sperm counts may become extremely low or even absent
Testicular volume may decrease
The Endocrine Society recommends against beginning testosterone therapy in men who are planning fertility in the near term.
A man who wants children now or in the future should therefore discuss reproductive goals before starting TRT.
Depending on the situation, evaluation by a reproductive urologist or another fertility specialist may be appropriate.
TRT should not be presented to a young man as though it is simply another vitamin or wellness supplement.
Does TRT Cause Prostate Cancer?
The relationship between testosterone and prostate health is more complicated than the common statement that "testosterone causes prostate cancer."
TRT is not prescribed with the assumption that increasing testosterone automatically causes prostate cancer.
However, prostate health still matters before and during treatment.
The Endocrine Society recommends against initiating testosterone therapy in certain men with known prostate cancer, suspicious prostate findings, or certain elevated PSA levels without appropriate further evaluation. It also recommends individualized discussion regarding prostate monitoring based on age and risk.
Depending on age, risk factors, history, symptoms, and shared decision-making, evaluation may include:
PSA testing
Review of urinary symptoms
Prostate examination when clinically indicated
Urology referral for concerning findings
TRT should complement appropriate preventive healthcare—not replace it.
What About Sleep Apnea?
Sleep deserves special attention in men being evaluated for low testosterone.
Poor sleep can contribute to fatigue, low motivation, metabolic dysfunction, sexual symptoms, and impaired quality of life—many of the same complaints attributed to low testosterone.
Untreated severe obstructive sleep apnea is also listed by the Endocrine Society among conditions in which testosterone therapy should not be initiated until appropriately addressed.
Men who have significant snoring, witnessed pauses in breathing, daytime sleepiness, resistant hypertension, or other features suggesting sleep apnea may need further evaluation.
Sometimes the most important intervention is not another hormone prescription.
Who Should Be Particularly Cautious About TRT?
Testosterone therapy may be inappropriate or require additional evaluation in men with conditions such as:
Known or suspected prostate cancer
Male breast cancer
Elevated hematocrit
Untreated severe obstructive sleep apnea
Significant lower urinary tract symptoms
Uncontrolled heart failure
Recent heart attack or stroke
Certain clotting disorders
Abnormal prostate findings
Fertility goals in the near future
The Endocrine Society specifically identifies several of these situations as reasons to avoid initiating testosterone until the clinical issue has been appropriately evaluated or addressed.
Individual circumstances vary, which is why TRT should be prescribed as medical therapy rather than as a standardized "optimization" protocol.
How Is TRT Monitored?
Starting testosterone is the beginning of treatment—not the end of the evaluation.
Follow-up should determine:
Whether symptoms are actually improving.
Whether testosterone exposure is appropriate.
Whether side effects are developing.
Whether continued treatment still makes sense.
Depending on the patient and formulation, monitoring may include:
Total testosterone
Free testosterone when clinically useful
Complete blood count
Hemoglobin and hematocrit
Blood pressure
PSA when appropriate
Prostate or urinary symptoms
Sexual function
Fertility considerations
Acne or skin changes
Fluid retention
Mood and sleep
Treatment adherence
Cardiovascular and metabolic health
The Endocrine Society recommends reassessing patients after testosterone is started for treatment response, adverse effects, and compliance with therapy.
At Ask Dr. Hu's Hormone Replacement Therapy program, treatment may include individualized laboratory evaluation and ongoing monitoring based on the patient's medical history, symptoms, treatment response, risk factors, and goals.
How Quickly Does TRT Work?
There is no single timeline.
Some symptoms may begin changing within several weeks, while changes in body composition, blood counts, bone health, or other physiologic effects can take considerably longer.
Importantly, treatment should not be judged solely by whether the laboratory testosterone number increased.
The more meaningful questions are:
Are the symptoms that led to treatment improving?
Has quality of life meaningfully changed?
Are side effects occurring?
Are laboratory markers remaining safe?
Is the dose appropriate?
Does the original diagnosis still make sense?
If testosterone levels normalize but the symptoms that led to treatment remain unchanged, the physician should reconsider whether testosterone deficiency was truly responsible for those symptoms.
Is Testosterone Injection Better Than Gel?
Neither is universally better.
Testosterone Injections
Potential advantages include:
Reliable absorption
Relatively low cost with many formulations
Flexible dosing
No risk of medication transfer to another person
Less frequent administration than daily gels
Potential disadvantages include:
Needles
Injection-site reactions
Peak-and-trough hormone fluctuations depending on dosing
Need for proper administration technique
Testosterone Gels
Potential advantages include:
No injection
Daily administration
Relatively steady testosterone exposure
Easy discontinuation or adjustment
Potential disadvantages include:
Daily application
Variable skin absorption
Skin irritation
Potential transfer to partners or children through contact with treated skin
Often higher cost depending on the medication and insurance
Testosterone Pellets
Pellets provide longer-lasting testosterone delivery and avoid frequent medication administration.
However, they require an implantation procedure and cannot be adjusted as quickly after placement.
The best formulation is the one that balances safety, effectiveness, cost, convenience, monitoring, and the patient's preferences.
You can compare these options in more detail in Types of HRT: Pills, Patches, Gels, Injections, and Pellets.
Do You Have to Stay on TRT Forever?
Not necessarily—but this question should be discussed before treatment begins.
If a man has permanent primary or secondary hypogonadism, long-term replacement may be appropriate.
If low testosterone developed in association with a potentially reversible factor such as obesity, medication use, severe illness, or another treatable condition, the situation may be different.
External testosterone also suppresses the body's own testosterone production during treatment, so stopping therapy may result in a period of low testosterone while the hypothalamic-pituitary-testicular axis recovers.
Recovery varies considerably.
This is another reason TRT should not be started casually. A patient should understand the potential long-term implications before beginning therapy.
Can Lifestyle Changes Raise Testosterone?
Sometimes.
Lifestyle treatment will not correct every form of hypogonadism, particularly when testosterone deficiency results from permanent testicular or pituitary disease.
However, overall metabolic health can substantially influence testosterone levels and testosterone-related symptoms.
Important factors may include:
Achieving a healthier body composition
Resistance training
Regular physical activity
Adequate sleep
Evaluation and treatment of sleep apnea
Adequate calorie and protein intake
Limiting excessive alcohol intake
Managing diabetes and metabolic disease
Reviewing medications that may affect hormones
A good testosterone evaluation should therefore consider the entire patient rather than treating the laboratory result in isolation.
TRT Should Be Personalized, Not "Optimized" to a Number
One of the biggest problems in modern hormone medicine is the idea that every man should have testosterone at a predetermined "optimal" level.
Human physiology does not work that way.
A testosterone level that is appropriate for one patient may not represent the same clinical situation in another.
Age, symptoms, SHBG, medications, body composition, sleep, fertility goals, pituitary function, laboratory timing, underlying disease, and numerous other factors influence interpretation.
Appropriate TRT asks:
Does this man have clinically meaningful testosterone deficiency, and will treatment likely provide more benefit than risk?
It does not simply ask:
How high can we make the testosterone number?
Questions to Ask Before Starting TRT
Before beginning treatment, a man should understand the answers to several questions:
Have I had appropriately timed testosterone testing?
Was the low result confirmed?
Do my symptoms actually fit testosterone deficiency?
Do we know why my testosterone is low?
Could another condition explain my symptoms?
Do I want children in the future?
What treatment options are available?
What are the potential side effects?
How will my hematocrit be monitored?
Should my prostate health be evaluated?
How will my blood pressure be monitored?
What testosterone level are we trying to achieve?
How will we decide whether treatment is actually working?
What happens if I eventually want to discontinue TRT?
A thoughtful physician should be able to discuss these issues before treatment begins.
The Bottom Line
Testosterone replacement therapy can be an important treatment for appropriately diagnosed testosterone deficiency.
It is not, however, a universal remedy for aging, fatigue, weight gain, low motivation, erectile dysfunction, or declining athletic performance.
Appropriate TRT begins with a clear diagnosis.
That means looking at:
Symptoms
Repeat testosterone measurements
The underlying cause of testosterone deficiency
Fertility goals
Cardiovascular health
Hematocrit
Prostate considerations
Sleep and metabolic health
Medications and medical history
Once treatment begins, monitoring remains essential.
For the right patient, carefully managed testosterone therapy may improve meaningful symptoms and quality of life. For the wrong patient—or at an unnecessarily high dose—it can create problems without addressing the actual cause of the symptoms.
If you would like a broader overview of hormone treatment, visit our Hormone Replacement Therapy Resource Center or read Hormone Replacement Therapy (HRT): A Complete Guide for Patients.
Patients in Arizona who would like an individualized hormone evaluation can also learn more about Hormone Replacement Therapy at Ask Dr. Hu.
Evidence-Based Medical References and E-E-A-T
This article was developed using current clinical guidance and evidence from established medical organizations and peer-reviewed research.
Key references include:
The Endocrine Society Clinical Practice Guideline on Testosterone Therapy in Men With Hypogonadism, which emphasizes diagnosis based on compatible symptoms plus consistently low testosterone levels, confirmation with repeat morning testing, evaluation for the underlying cause, fertility considerations, contraindications, and ongoing monitoring.
The U.S. Food and Drug Administration's current testosterone information regarding approved testosterone therapy and appropriate use.
The FDA's 2025 class-wide testosterone labeling update, reflecting findings from the TRAVERSE cardiovascular outcomes trial and ambulatory blood-pressure studies.
The peer-reviewed TRAVERSE trial, published in the New England Journal of Medicine, evaluating cardiovascular safety of testosterone replacement therapy in men with hypogonadism and cardiovascular disease or elevated cardiovascular risk.
The American Urological Association Testosterone Deficiency Guideline, which provides additional clinical guidance regarding diagnosis, treatment, fertility, and monitoring of testosterone deficiency.
Medical recommendations and medication labeling can change as new evidence becomes available. Testosterone therapy should therefore be individualized and periodically reassessed rather than managed according to a fixed protocol.
About the Author
YiQiu Hu, NMD
Dr. YiQiu Hu is an Arizona-licensed naturopathic physician and founder of Ask Dr. Hu. His clinical work focuses on concierge medicine, preventive healthcare, health optimization, laboratory evaluation, medical weight management, hormone care, integrative pain management, and individualized treatment planning.
At Ask Dr. Hu, Dr. Hu provides personalized medical care for patients throughout Arizona with an emphasis on thorough evaluation, clear explanations, evidence-informed treatment options, and ongoing physician-patient relationships.
This article is intended for general educational purposes and does not replace individualized medical evaluation, diagnosis, or treatment.