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Men's health

Testosterone Replacement Therapy: Benefits, Side Effects, and What to Weigh Before Starting

Testosterone replacement therapy can improve energy, mood, sex drive, and bone density in men with clinically confirmed low testosterone. It also suppresses fertility while in use and carries cardiovascular and prostate considerations, so candidates need baseline labs and ongoing monitoring with a clinician who knows their full health picture.

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Who is generally considered a candidate for TRT?

Clinical guidelines do not recommend TRT for everyone with a low-looking lab number. The AUA Testosterone Deficiency Guideline recommends it for men who have both consistently low testosterone on at least two morning blood draws and symptoms plausibly caused by that deficiency — reduced sex drive, erectile difficulty, unexplained fatigue, loss of muscle or bone, or depressed mood 1.

Before starting TRT, a clinician should identify and, where possible, treat reversible causes of low testosterone — obesity, untreated sleep apnea, certain medications, or chronic illness — because addressing these can raise testosterone on their own without hormonal intervention 1.

What are the common side effects of TRT?

Most side effects are dose-related and manageable with monitoring.

Polycythemia (increase in red blood cell production) is one of the most clinically important: thickened blood raises the risk of clots and cardiovascular events [1, 2]. Hematocrit is checked regularly throughout treatment.

Acne and oily skin are common, particularly in the early months.

Fluid retention can cause mild swelling, especially in the lower legs.

Testicular atrophy occurs because the body's own hormone signaling is suppressed by exogenous testosterone — the testicles receive less stimulation and shrink in size. This is expected and does not reverse while TRT continues 1.

Gynecomastia (breast tissue sensitivity or mild growth) can develop as some testosterone converts to estrogen in the body.

How does TRT affect fertility?

This is among the most critical and frequently underestimated effects. Testosterone replacement suppresses the pituitary signals that drive sperm production. For most men on TRT, sperm counts fall dramatically — sometimes to zero 3. Recovery after stopping TRT can take many months to over a year, and in some cases may be incomplete.

If fathering biological children is a goal now or in the future, this conversation must happen before starting TRT. Alternative approaches — such as clomiphene citrate or gonadotropin-based therapy — can raise testosterone while preserving fertility 3. Make sure your clinician knows your reproductive plans before any prescription is written.

What are the cardiovascular and prostate considerations?

The relationship between TRT and cardiovascular risk has been studied extensively. Current evidence is nuanced: untreated severe testosterone deficiency is itself associated with cardiovascular risk, and a meta-analysis of randomized trials found no statistically significant increase in major cardiovascular events with TRT — but the polycythemia effect and individual cardiovascular risk profile remain important considerations 2. Men with a history of blood clots, recent cardiac events, or significant cardiovascular risk factors require careful evaluation before starting.

The prostate is another consideration. TRT can increase PSA (prostate-specific antigen) and may stimulate benign prostate growth. It is generally avoided — or used only with very close monitoring — in men with known or suspected prostate cancer 1. Regular PSA checks are standard practice for most men on TRT.

What are the delivery options and their trade-offs?

TRT comes in several forms, each with different practical considerations.

Injections (intramuscular or subcutaneous) are low-cost and effective but produce hormone peaks and troughs that some men find uncomfortable.

Topical gels and creams maintain steadier levels but carry a transfer risk — the hormone can be absorbed by a partner or child through skin-to-skin contact. This is a real safety concern when young children are in the home 1.

Patches and subcutaneous pellets offer other pharmacokinetic profiles and may suit particular lifestyles.

No form is universally best. The choice depends on lifestyle, household composition, monitoring compliance, cost, and personal preference — and should be made with a clinician who knows your situation.

What does ongoing monitoring look like?

TRT is not a one-time decision. Standard practice involves periodic blood tests — typically checking testosterone levels, hematocrit, and PSA — along with regular assessments of symptom response 1. If hematocrit rises too high, a dose reduction or temporary pause may be needed. The goal is the lowest effective dose that controls symptoms, not maximizing the number.

Common questions

Can I stop TRT if I change my mind?

Yes, but stopping has its own effects. The body's own testosterone production, suppressed during TRT, may take weeks to months to recover. Some men experience a period of low testosterone symptoms after stopping. Your clinician can guide a safe taper if stopping is the goal.

Will TRT help if I just feel tired and my testosterone is borderline?

Not necessarily. Clinical guidelines recommend TRT for men with both confirmed low levels and symptoms attributable to that deficiency — not for borderline levels alone, and not as a first step before ruling out other fatigue causes. A thorough evaluation first leads to better outcomes.

Does TRT cause prostate cancer?

Current evidence does not establish that TRT causes prostate cancer. However, it can stimulate growth of existing prostate cancer and increases PSA. Men with known or suspected prostate cancer generally should not use TRT, and PSA monitoring is standard for those who do.

What is the transfer risk with testosterone gel?

If a partner or child touches your skin where the gel has been applied before it dries and is washed off, they can absorb testosterone and develop hormonal effects. Young children are particularly vulnerable. Covering the application site and washing hands thoroughly after applying significantly reduces this risk.

I want biological children in the future. Can I still consider TRT?

Possibly — but the fertility discussion must come first. TRT significantly suppresses sperm production. If future biological children are a priority, a clinician may recommend alternatives that raise testosterone while preserving fertility, such as clomiphene or human chorionic gonadotropin.

Talk to a clinician

Nina Osei, NP — Nurse Practitioner

checkups, refills & skin. Gale can match you with a licensed clinician for a visit.

Find care →

Warning signs while on TRT

  • —Sudden shortness of breath, chest pain, or leg swelling — go to the emergency department (possible clot or cardiac event)
  • —Severe or rapidly worsening headache while on TRT
  • —Signs of gel transfer in a child or female partner: unexpected hair growth, acne, or behavioral changes — stop skin contact and contact a clinician promptly
  • —Difficulty urinating or sudden change in urinary flow — discuss with a clinician promptly

If you develop sudden chest pain, shortness of breath, or leg swelling while on testosterone therapy, call 911 or go to the nearest emergency department.

This article is general health education and does not constitute medical advice or a prescription recommendation. Testosterone replacement therapy is a medical treatment with meaningful risks; decisions about starting, adjusting, or stopping it must be made with a qualified clinician who knows your full medical history.

References

  1. 1.Mulhall JP, Trost LW, Brannigan RE, et al. (2018). Evaluation and Management of Testosterone Deficiency: AUA Guideline. Journal of Urology. doi:10.1016/j.juro.2018.03.115 ✓Indications for TRT, common side effects including polycythemia and testicular atrophy, prostate monitoring, delivery form considerations, and the fertility suppression effect
  2. 2.Jaiswal V, Sawhney A, Nebuwa C, et al. (2024). Association between Testosterone Replacement Therapy and Cardiovascular Outcomes: A Meta-analysis of 30 Randomized Controlled Trials. Progress in Cardiovascular Diseases. doi:10.1016/j.pcad.2024.04.001 ✓Nuanced evidence on TRT and cardiovascular outcomes, supporting the statement that current evidence does not show a statistically significant increase in major cardiovascular events while acknowledging ongoing uncertainty
  3. 3.Schlegel PN, Sigman M, Collura B, et al. (2021). Diagnosis and Treatment of Infertility in Men: AUA/ASRM Guideline Part I. Journal of Urology. doi:10.1097/JU.0000000000001521 ✓TRT's suppressive effect on sperm production, the potential for incomplete recovery after stopping, and alternative fertility-preserving approaches such as clomiphene and gonadotropin therapy

3 sources, numbered by first appearance. General health information, not medical advice — synthetic demonstration content.