Start with the basics
What is TRT?
Testosterone replacement therapy is prescription treatment for men whose bodies do not produce enough testosterone. Testosterone contributes to:
- Sexual function
- Muscle maintenance
- Bone health
- Red blood cell production
TRT is intended for appropriately diagnosed testosterone deficiency, also called male hypogonadism. Treatment decisions require symptoms, laboratory findings, and a medical evaluation. [1, 2]
Symptoms and possible causes
Signs that deserve a conversation
Possible signs of low testosterone include:
- Reduced sexual desire or fewer spontaneous erections
- Decreased muscle mass
- Persistent fatigue or reduced endurance
- Irritability, depressed mood, or difficulty concentrating
- Low bone density or unexplained anemia
- Fertility problems
These symptoms overlap with many other conditions. A symptom checklist can start a conversation, but it cannot diagnose low testosterone. [1, 3]
Why testosterone may be low
Low testosterone can result from:
- Testicular injury or disease
- Pituitary disorders
- Certain medications
- Obesity
- Sleep disorders
- Other medical conditions
- Previous anabolic steroid use
Some causes may be reversible. Improving sleep, addressing obesity, or changing a contributing medication under medical supervision may be appropriate before considering TRT. [1, 8]
Diagnosis
How is low testosterone diagnosed?
The American Urological Association considers total testosterone below 300 ng/dL a reasonable threshold supporting a diagnosis. A number alone does not determine who needs treatment. Symptoms, repeat testing, and a medical evaluation also matter. [3]
A typical evaluation includes:
- Symptom and health historyThis may include medications, sleep, fertility goals, and previous hormone use.
- Two testosterone measurementsTesting is generally performed on separate mornings. The Endocrine Society recommends fasting morning testing.
- Additional hormone testing when indicatedFree testosterone may help clarify borderline results or situations in which sex hormone-binding globulin (SHBG) affects interpretation.
- Testing to identify the causeLH and FSH can help distinguish a testicular problem from a problem involving hormonal signals from the brain. [2]
An isolated low result during an illness should not automatically lead to a prescription. [2]
Potential benefits and limitations
What can TRT improve?
For men with confirmed testosterone deficiency, treatment may improve:
- Sexual desire
- Some aspects of sexual function
- Lean body mass
- Bone density
- Certain cases of anemia [1, 3]
Benefits vary, and different symptoms respond differently.
In NIH-supported trials involving men age 65 and older with low testosterone, treatment improved sexual function and produced modest mood benefits. It did not significantly improve the primary fatigue outcome. These findings should not be treated as a promise for every patient. [4]
What TRT may not fix
TRT should not be presented as a guaranteed solution for:
- Brain fog
- Depression
- Weight loss
- Low energy
- Relationship difficulties
Evidence for improved cognition, energy, and overall quality of life remains inconclusive. [3]
Treatment options
Common prescription approaches
Availability and suitability depend on the product, your health, and the prescribing clinician.
| Option | What to consider |
|---|---|
| Testosterone injections | The schedule and injection technique depend on the formulation. Some products may be suitable for prescribed home use. |
| Topical gels | Applied regularly. Precautions are needed to prevent transfer to partners or children. |
| Pellets | Inserted beneath the skin through a procedure. Treatment changes require planning with the clinician. |
| Oral testosterone | Certain prescription formulations are available. Use and monitoring follow the specific product instructions. |
There is no single best option for everyone. Discuss:
Monitoring and safety
What does ongoing monitoring involve?
Follow-up helps determine whether treatment is working and whether it remains appropriate. Monitoring commonly includes:
- Symptoms and treatment response
- Side effects and adherence
- Testosterone levels, with blood draws timed to the formulation
- Hemoglobin and hematocrit
- Blood pressure
- Prostate assessment and PSA testing when appropriate for age, risk, and shared decision-making
The AUA recommends measuring testosterone every 6–12 months during ongoing treatment. Earlier assessment may be needed after starting or changing therapy. [2, 3, 5]
Possible side effects
Potential effects include:
- Acne
- Injection-site irritation
- Fluid retention
- Breast tenderness
- Increased blood pressure
- Reduced sperm production
- Elevated hematocrit [2, 5]
When extra caution is needed
Clinicians generally avoid initiating TRT in men who:
- Are planning fertility soon
- Have active prostate or breast cancer
- Have elevated hematocrit
- Have untreated severe obstructive sleep apnea
- Have uncontrolled heart failure
- Recently experienced a heart attack or stroke
- Have thrombophilia
Some findings require further specialist evaluation. [2]
What about heart health?
In February 2025, the FDA announced the removal of boxed-warning language about increased adverse cardiovascular outcomes after reviewing the TRAVERSE trial. The FDA also required warnings about increased blood pressure and retained limitations concerning age-related hypogonadism.
This update does not establish that TRT is risk-free or appropriate for everyone. [7]
TRT FAQs
Is TRT the same as a testosterone booster?
No. TRT uses prescription testosterone. Over-the-counter products marketed as “boosters” are not equivalent to replacement therapy. [8]
Can TRT affect fertility?
Will TRT fix erectile dysfunction?
It may help when testosterone deficiency contributes to erectile dysfunction. However, erection problems can have other causes and may require separate evaluation and treatment. [8]
How quickly will I notice a change?
Do I need the highest testosterone number possible?
No. The clinical goal is symptom improvement with testosterone in a physiologic range and appropriate safety monitoring.
A higher number is not automatically a better result. [2]
Is treatment lifelong?
Can I stop once I feel better?
Do not change or stop treatment without discussing it with the prescriber.
Feeling better does not establish that the underlying condition has resolved. [5]
NEXT STEPS
Better answers start with a proper evaluation.
You do not have to guess whether hormones are part of the problem.
Start by:
- Reviewing your symptoms and health history
- Confirming what your laboratory results show
- Discussing fertility goals and treatment preferences
- Creating a monitoring plan with a licensed clinician
Not sure yet? Take the 2-minute symptom check. Or see men's care and pricing and how the process works. For your partner: women's HRT & perimenopause. On the blog: why men get told to toughen up.
This page provides general education and does not diagnose a condition or replace individualized medical advice. Prescription treatment requires evaluation by a licensed clinician.
Sources and further reading
- Endocrine Society: Hypogonadism in Men — Patient overview of symptoms, causes, treatment, and fertility considerations.
- Endocrine Society: Testosterone Therapy Clinical Practice Guideline — Diagnosis, free testosterone, contraindications, treatment goals, and monitoring.
- American Urological Association: Testosterone Deficiency Guideline — Diagnostic thresholds, counseling, and follow-up. Published guideline PDF.
- National Institute on Aging: NIH-Supported Testosterone Trials — Findings on sexual function, mood, and fatigue in older men.
- MedlinePlus: Testosterone Injection — Use, precautions, side effects, and blood-pressure monitoring.
- MedlinePlus: Oral Testosterone — Product-specific use and safety information.
- FDA: February 2025 Testosterone Labeling Changes — Updated cardiovascular and blood-pressure labeling.
- MedlinePlus: Could You Have Low Testosterone? — Patient guide to causes, diagnosis, and treatment.