Testosterone (TRT)
Testosterone Replacement Therapy
Hormone Replacement Therapy
Evidence Level: Strong Evidence
Multiple large human trials, FDA approval, established safety profile
Regulatory Status: FDA-approved for treatment of hypogonadism (low testosterone)
Testosterone replacement therapy (TRT) is the medical treatment for men with clinically low testosterone (hypogonadism). It involves supplementing testosterone through injections, gels, patches, or pellets to bring levels back to a healthy range. When properly prescribed and monitored, TRT can significantly improve energy, mood, libido, body composition, and overall quality of life. It's one of the most impactful hormone interventions available, but it's not without trade-offs.
How It Works
What testosterone does:
• Maintains muscle mass and bone density
• Regulates fat distribution and metabolism
• Drives libido and sexual function
• Affects mood, energy, and cognitive function
• Supports red blood cell production
Why levels decline:
Testosterone naturally decreases about 1% per year after age 30. But many men experience faster declines due to obesity, stress, poor sleep, or underlying medical conditions. Some men have primary hypogonadism (the testes don't produce enough) or secondary hypogonadism (the brain doesn't signal the testes properly).
How TRT works:
External testosterone replaces what your body isn't making. This raises blood testosterone levels, restoring the hormone's effects throughout your body. The trade-off: when you add external testosterone, your body's natural production shuts down. The testes receive less signaling and produce less testosterone and sperm.
Potential Benefits
- Improved energy and reduced fatigue
- Increased muscle mass and reduced body fat (with exercise)
- Enhanced libido and sexual function
- Better mood and reduced depression symptoms
- Improved cognitive function and mental clarity
- Increased bone mineral density, though a large trial found this did not reduce fractures
- Better motivation and sense of well-being
Risks & Considerations
- Suppresses natural testosterone production (usually permanent with long-term use)
- Reduces sperm production (can cause infertility, often reversible with HCG or stopping TRT)
- May increase hematocrit/red blood cells (requires monitoring; can increase clot risk)
- Possible acne and oily skin
- Potential for estrogen conversion (may need estrogen management)
- Testicular atrophy (shrinkage) due to reduced natural production
- Requires lifelong commitment for most users
- Mood changes possible during dose adjustments
- Cardiovascular risk debate (recent studies suggest it's safer than once thought)
Dosing Information
TRT protocols vary significantly between clinics and individual needs. The goal is achieving testosterone levels in the upper-normal range while minimizing side effects.
- •Typical injection dose: 100-200mg testosterone cypionate/enanthate weekly
- •Some protocols use twice-weekly injections for more stable levels
- •Gels: Daily application (AndroGel, Testim), convenient but expensive and transfer risk
- •Patches: Daily (Androderm), less common due to skin irritation
- •Pellets: Implanted every 3-6 months (Testopel), convenient but less adjustable
- •Target: Most aim for Total T of 600-900 ng/dL (varies by individual)
- •Free testosterone and SHBG matter as much as total testosterone
Practical Tips
- 1Get comprehensive baseline testing before starting (Total T, Free T, SHBG, estradiol, CBC, PSA)
- 2Test testosterone in the morning when levels are highest
- 3Self-injection is common and not as intimidating as it sounds (subcutaneous works well)
- 4Monitor hematocrit every 3-6 months (donate blood if it gets too high)
- 5Consider HCG if fertility preservation is important (maintains testicular function)
- 6Dial in your protocol over months, expect adjustments
- 7Some men need estrogen management (anastrozole) if they aromatize heavily
- 8Lifestyle still matters: TRT amplifies results from exercise and good nutrition
Key Research
Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE)
New England Journal of Medicine, 2023
TRT did not increase major adverse cardiovascular events versus placebo in middle-aged and older men with hypogonadism and pre-existing cardiovascular disease or high risk of it. This addressed the field's major long-standing safety concern.
View StudyEffects of Testosterone Treatment in Older Men (The Testosterone Trials)
New England Journal of Medicine, 2016
TRT improved sexual function and, to a lesser extent, mood and walking distance in men over 65 with low testosterone. Benefits were moderate rather than dramatic.
View StudyTestosterone Treatment and Fractures in Men with Hypogonadism
New England Journal of Medicine, 2024
Testosterone increases bone density, but this 5,204-man subtrial of TRAVERSE found MORE clinical fractures on testosterone, not fewer: 3.50% versus 2.46% on placebo over a median 3.19 years (hazard ratio 1.43, 95% CI 1.04 to 1.97). Higher bone density did not translate into fewer broken bones, which is a useful reminder that a good biomarker is not the same as a good outcome.
View StudyConsidering testosterone therapy?
Work with a provider experienced in hormone optimization.
Always consult a healthcare provider before starting any treatment.
Frequently Asked Questions
What testosterone level is considered low enough for TRT?
Most guidelines consider total testosterone below 300 ng/dL as low, though symptoms matter more than numbers. Some men have symptoms at 350-400 ng/dL, while others feel fine at 280 ng/dL. The context matters: age, symptoms, free testosterone levels, and SHBG all factor in. Most clinicians treat based on the combination of low levels AND symptoms.
Will TRT make me infertile?
TRT typically suppresses sperm production significantly and can cause infertility while on therapy. However, this is often reversible after stopping TRT, especially if treatment duration was shorter. If fertility preservation is important, discuss HCG (human chorionic gonadotropin) with your doctor, it maintains testicular function and sperm production while on TRT.
How long does it take to feel the effects of TRT?
Different effects appear on different timelines. Improved energy and mood may be noticed within 2-4 weeks. Libido improvements often come within 3-6 weeks. Body composition changes (more muscle, less fat) typically take 3-6 months of consistent therapy with proper diet and exercise. Full effects may take 6-12 months to stabilize.
Is TRT safe for the heart?
The 2023 TRAVERSE trial (the largest TRT cardiovascular safety study) found that TRT did not increase cardiovascular events in men with pre-existing heart disease risk. This was reassuring after earlier concerns. However, TRT can increase hematocrit (red blood cell concentration), which may increase clot risk if not monitored. Regular blood work is essential.
Does TRT cause prostate cancer?
Current evidence does not support the old belief that TRT causes prostate cancer. Studies show TRT doesn't increase prostate cancer risk in men without existing cancer. However, testosterone can accelerate growth of existing prostate cancer, so PSA monitoring is standard, and TRT is avoided in men with active prostate cancer.
Can I do TRT with injections I give myself at home?
Yes, self-injection at home is the most common TRT method. Testosterone cypionate or enanthate is typically injected subcutaneously (into fat) or intramuscularly once or twice weekly. Most men find it straightforward after initial instruction. It's more cost-effective than gels and provides more stable levels than less frequent injection schedules.
What is the difference between TRT and steroids?
TRT uses testosterone at doses that restore normal physiological levels (typically 100-200mg/week, targeting 600-900 ng/dL). Anabolic steroid abuse uses much higher doses, often with additional compounds, to achieve supraphysiological levels for muscle building. TRT is medical therapy; steroid abuse carries significantly higher health risks.
Will my natural testosterone production recover if I stop TRT?
It depends on duration and pre-TRT levels. After long-term TRT (years), natural production may not fully recover, many men become TRT-dependent. After shorter courses (months), recovery is more likely, though it may take weeks to months and levels may not reach pre-TRT values. HCG during TRT helps maintain testicular function and improves recovery odds.
Related Reading
Disclaimer: This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider before starting any treatment. Evidence levels and regulatory status can change, this content was last updated December 2025.