The Framing: TRT Is Safe For Appropriate Men With Proper Monitoring
Before the specifics, the honest framing: TRT is safe for most men when prescribed appropriately and monitored properly. The TRAVERSE trial (the largest TRT safety study) found no increased cardiovascular risk in men screened for existing cardiovascular disease and monitored closely during treatment.
However: TRT is not risk-free. Side effects range from cosmetic (acne) to manageable (testicular atrophy) to serious (polycythaemia). Understanding these is essential for informed consent.
The critical point: most side effects are manageable with good clinical oversight. You need proper monitoring, experienced doctors, and willingness to adjust protocol if side effects emerge.
This guide covers real side effects — not worst-case fear-mongering, but honest discussion of what can happen and how it's typically managed.
Acne and Skin Changes
Acne is one of the most common side effects of TRT, particularly in the early weeks of treatment.
What happens:
Testosterone increases sebaceous gland activity (oil production). Additionally, testosterone is converted to DHT (dihydrotestosterone) in the skin by the enzyme 5-alpha reductase. DHT is highly androgenic and stimulates sebum production and skin inflammation.
Acne typically appears within 2–4 weeks of starting TRT, localising to the shoulders, back, and chest — areas with high androgen receptor density.
Frequency: 30–50% of men on TRT experience noticeable acne.
Timeline: Usually improves after 6–8 weeks as the skin adapts to new testosterone levels. The initial acne is often worse than long-term acne.
Management:
- Benzoyl peroxide wash (5–10%): Morning and evening wash. This is the gold standard and often sufficient.
- Topical retinoid: If benzoyl peroxide alone isn't adequate.
- Oral antibiotics: Low-dose doxycycline for 4–8 weeks if acne is severe (addresses both sebum production and bacterial colonisation).
- 5-alpha reductase inhibitor (finasteride or dutasteride): Reduces DHT production. This is effective but comes with its own side effects and isn't routinely used for acne alone.
For most men, benzoyl peroxide wash is sufficient and acne resolves within 2–3 months despite continuing TRT.
Polycythaemia: The Main Haematological Concern
This is the most serious and common side effect of TRT. It deserves careful explanation.
What is polycythaemia?
Polycythaemia is an elevated red blood cell count (haematocrit > 54% or haemoglobin > 17 g/dL). Testosterone stimulates erythropoietin (EPO) production in the kidneys, which increases red blood cell production.
A higher red blood cell count makes blood thicker and more viscous. This increases the risk of thrombosis (blood clots), which can lead to deep vein thrombosis (DVT), pulmonary embolism (PE), or stroke.
Frequency: 10–15% of men on TRT develop elevated haematocrit requiring intervention.
Risk factors for polycythaemia:
- Baseline elevated haematocrit
- High-dose TRT (above 200 mg testosterone weekly)
- Injection frequency (less frequent injections produce higher peaks, more likely to trigger EPO)
- Existing sleep apnoea (hypoxia stimulates EPO)
- Smoking
- Dehydration
Monitoring:
Haematocrit (and haemoglobin) should be checked:
- Baseline (before starting TRT)
- 4–6 weeks after starting TRT (during the rise phase)
- Every 3–6 months once stable
- Any time you change dose
Most guidelines recommend keeping haematocrit < 54% and haemoglobin < 17 g/dL.
Management:
- Dose reduction: The most straightforward approach. Reducing testosterone dose from 200 mg/week to 150 mg/week often brings haematocrit down.
- Injection frequency: Switching from every 2 weeks to every week (or subcutaneous dosing) reduces the peak testosterone level and associated EPO stimulation.
- Phlebotomy (blood donation): Therapeutic removal of a unit of blood (500 ml) reduces haematocrit acutely. This is used as a short-term measure if haematocrit spikes above 55%.
- Aspirin: Low-dose aspirin (75–100 mg daily) slightly reduces thrombosis risk if haematocrit is modestly elevated.
For the vast majority of men with elevated haematocrit on TRT, dose reduction or injection frequency adjustment resolves the issue. Haematocrit is easy to monitor and manage — this is not a reason to avoid TRT if you otherwise need it, but it does require monitoring.
Testicular Atrophy and Loss of Testicular Function
This is inevitable on TRT without mitigation.
What happens:
Exogenous testosterone suppresses LH and FSH via negative feedback. Without LH stimulation, the testes stop producing testosterone and sperm. The testicular tissue (Leydig and Sertoli cells) gradually atrophy from disuse.
Testicular volume decreases visibly (testes become noticeably smaller), and testicular firmness decreases.
Frequency: 100% of men on TRT experience testicular atrophy unless HCG is co-administered.
Timeline: Noticeable atrophy develops over 6–12 months without HCG.
Reversibility: If TRT is stopped and the HPT axis recovers (or HCG is restarted), testicular function typically recovers over 3–6 months. However, if you've been on TRT without HCG for years, recovery can take longer and may be incomplete.
Management: HCG Co-Administration
Human chorionic gonadotropin (HCG) acts like LH, maintaining testicular testosterone production and spermatogenesis even while you're on TRT.
Typical protocol: 500–1000 IU HCG 2–3 times per week (usually given subcutaneously).
With HCG co-administration:
- Testicular atrophy is minimal or absent
- Testicular function is largely maintained
- Fertility is preserved (spermatogenesis continues)
- Testicular sensitivity to exogenous testosterone improves (better response to future testosterone)
Cost: HCG is additional cost (£50–100/month in the UK typically).
Important: Many TRT clinics now include HCG in standard protocols because of this. If your clinic isn't offering HCG and you want to preserve testicular function and fertility, you should ask for it.
Fertility Suppression and Sperm Production
On TRT without HCG, sperm production shuts down due to suppressed FSH and LH.
What happens:
Sperm production requires FSH stimulation of Sertoli cells. On TRT, FSH is suppressed, and spermatogenesis stops. A semen analysis typically shows either very low sperm count (oligozoospermia) or complete absence of sperm (azoospermia).
Timeline: Sperm suppression develops over 4–8 weeks, and complete azoospermia by 8–12 weeks.
Reversibility: After stopping TRT, sperm production recovers over 3–6 months (full recovery can take 6–12 months). However, if you were infertile before TRT, TRT won't improve that — you'll just remain infertile during treatment.
Management:
- HCG co-administration: Maintains sperm production (though not 100% — sperm count may still drop by 50% or more, but fertility is usually maintained).
- Enclomiphene or clomiphene: If you want to maintain fertility and come off TRT, these drugs restore LH/FSH and restart testosterone production. They don't work well for actual TRT (unstable testosterone), but they're useful for restart after TRT.
- Sperm banking: If you're young and planning TRT long-term, banking sperm before starting is an option (though expensive — £500–1000).
Critical: If you want to have biological children in the future, this is a serious consideration. Discuss it with your doctor before starting TRT. HCG co-administration is the standard solution.
Fluid Retention
Some men retain fluid on TRT, particularly in the face, ankles, and hands.
What happens:
Testosterone increases sodium reabsorption in the kidneys (via androgen receptors) and stimulates arginine vasopressin (AVP) secretion. Both mechanisms increase water retention.
Additionally, if testosterone converts to oestradiol (aromatisation), elevated oestradiol also promotes sodium and water retention.
Frequency: 10–20% of men notice noticeable fluid retention.
Timeline: Usually appears within 2–4 weeks and stabilises by 8 weeks.
Management:
- Reduce sodium intake: Often helpful, particularly if oestradiol is also elevated.
- Monitor oestradiol: If elevated, reducing aromatisation via dose reduction or (rarely) aromatase inhibitors may help.
- Diuretics: Rarely needed for TRT-related fluid retention in men without heart disease or hypertension.
For most men, mild fluid retention settles or is negligible. If retention is significant, it's usually addressing underlying oestradiol elevation that's the solution.
Elevated Oestradiol
Testosterone is aromatised (converted) to oestradiol by the enzyme aromatase, particularly in adipose tissue.
What happens:
Higher testosterone levels mean more oestradiol production. Additionally, some men have higher baseline aromatase activity. Oestradiol elevation can cause:
- Breast tenderness or gynecomastia (breast tissue growth)
- Mood changes (too much oestradiol impairs mood, similar to too little testosterone)
- Fluid retention
- Reduced libido (paradoxically, too much oestradiol suppresses it)
Oestradiol levels on TRT: Typically rise to 40–80 pg/mL (aim is usually 20–40 pg/mL).
Management — and why it matters:
Here's a critical issue: aromatase inhibitor (AI) overuse is a secondary problem on TRT.
- Dose reduction first: Reducing testosterone dose reduces aromatisation.
- Injection frequency: More frequent, lower-dose injections reduce peak testosterone and aromatisation.
- Aromatase inhibitors (anastrozole, letrozole): Should be used cautiously. Over-suppression of oestradiol (below 20 pg/mL) causes joint pain, reduced libido, and mood issues — essentially creating low-oestradiol problems while solving high-oestradiol problems.
If oestradiol is moderately elevated (40–60 pg/mL), it often doesn't require treatment. If it's very high (> 70 pg/mL) or causing symptoms, dose adjustment is typically better than adding AI.
Important: Gynecomastia (actual breast tissue growth) from TRT is rare if caught early. Breast tenderness alone is common and usually resolves. If actual gynecomastia develops, it may require surgical removal — it doesn't reliably reverse with AI or dose reduction.
Mood Changes on TRT
TRT can produce mood changes, though the direction varies.
Positive mood effects (common): Improved motivation, better mood, more confidence, reduced depression.
Negative mood effects (less common): Increased irritability, aggressive thoughts, mood instability. This is often related to:
- Oestradiol being too high or too low (either extreme impairs mood)
- Testosterone dose being too high (supra-physiologic levels can cause irritability)
- Baseline psychiatric issues being exacerbated
Management:
Most mood improvement on TRT is real and beneficial. If mood becomes problematic (irritability, aggression, unstable mood), it usually responds to:
- Dose reduction
- Oestradiol optimisation
- Addressing other lifestyle factors (sleep, stress)
Men with a history of bipolar disorder or significant psychiatric issues should be monitored closely during TRT.
Sleep Apnoea and Worsening of Existing Sleep Apnoea
TRT can worsen or unmask sleep apnoea.
What happens:
Testosterone increases muscle mass in the pharynx and may increase muscle relaxation during sleep, narrowing the airway. Additionally, oestradiol elevation can increase fluid retention, which can narrow airways.
If you have undiagnosed sleep apnoea, starting TRT might reveal it (you sleep worse, you're more aware of the apnoea).
Who's at risk: Men with existing sleep apnoea, obesity, thick neck circumference, or signs of sleep-disordered breathing.
Screening: Before starting TRT, your doctor should ask about snoring, daytime somnolence, and witnessed apnoeas. Men at risk should have sleep screening (at minimum, a home sleep test).
Management:
- Sleep study: If you have risk factors or worsen on TRT, get a sleep study.
- CPAP: If sleep apnoea is confirmed, CPAP is essential before or during TRT.
- Dose adjustment: Lower testosterone doses produce less muscle hypertrophy in the pharynx.
Sleep apnoea is a serious problem that can be independently harmful and also contributes to other TRT side effects (elevated haematocrit, hypertension, cardiovascular risk). If you have it, it must be addressed.
Cardiovascular and Thrombotic Events
This is the most feared side effect, so it deserves careful, honest discussion.
The research — TRAVERSE trial (2023):
The TRAVERSE trial was a large, randomised trial of TRT vs. placebo in over 5,000 men with low testosterone and cardiovascular risk factors. Results showed:
- No increased cardiovascular events in men adequately screened for existing disease
- No increased mortality
- Slight increase in non-fatal cardiovascular events in men who already had evidence of coronary artery disease at baseline
The key finding: TRT is safe for men without existing significant cardiovascular disease. TRT in men with known coronary artery disease is riskier.
What does happen:
TRT can elevate:
- Blood pressure (modest, 2–5 mmHg typically)
- LDL cholesterol (modest elevation, 5–10%)
- Haematocrit (covered above — major concern)
- Fibrinogen (blood clotting factor — slight elevation)
Any of these could theoretically increase thrombotic risk, but clinical evidence suggests that in screened men, the actual risk is low.
Who's at higher risk:
- Men with existing coronary artery disease
- Men with severe hypertension (uncontrolled)
- Men with significant thrombophilia (clotting disorders)
- Men with uncontrolled diabetes
- Heavy smokers
- Men with polycythaemia (unmanaged)
Management:
- Baseline screening: Electrocardiogram, blood pressure, lipid panel, possibly stress test if multiple risk factors.
- Regular monitoring: Blood pressure, haematocrit, lipid panel every 6–12 months.
- Modifiable risk factors: Stop smoking, manage weight, control blood pressure and diabetes.
- Dose appropriateness: Use the lowest effective dose (usually 100–200 mg/week), not excessive doses.
For appropriate men properly screened and monitored, TRT appears safe. But this requires actual oversight, not just a prescription with zero follow-up.
Prostate Issues
PSA (prostate-specific antigen) elevation:
TRT typically causes a modest PSA elevation (15–30% increase). This is expected and reflects normal prostate stimulation by testosterone.
Important: A PSA rise on TRT doesn't necessarily mean prostate cancer. However, if PSA rises unusually steeply (> 1.4 ng/mL per year), that warrants investigation.
Prostate cancer risk:
Large, long-term studies (TOM trial, Testosterone in Older Men with Mobility Limitations) found no increased prostate cancer risk in men on TRT compared to controls, over 3–4 years of follow-up.
However, men with a personal history of prostate cancer or significant family history are typically not candidates for TRT due to theoretical risk.
Management:
- Baseline PSA: Before starting TRT (optional in younger men without risk factors; essential in men > 50 or with risk factors).
- Repeat PSA: At 3–6 months, then annually.
- Digital rectal exam (DRE): At baseline and periodically (though evidence for DRE benefit is mixed).
If PSA rises steeply on TRT, investigation is warranted. If PSA is stable, TRT is safe to continue in most men.
Rarer Side Effects
Liver toxicity: Alkylated oral testosterone (methyltestosterone) can cause liver damage. Modern TRT (injections, gels, patches) does not. If you're on oral testosterone, regular liver function testing is needed.
Allergic reactions: Rare, but injectable testosterone can cause injection site reactions or true allergic responses.
Headaches: Some men develop or worsen migraines on TRT. Usually improves with dose adjustment.
Managing Side Effects: The Monitoring Protocol
Good TRT requires good monitoring. Ideally, here's what should be checked:
Baseline (before starting):
- Total and free testosterone
- LH, FSH, prolactin
- Oestradiol
- Full blood count (including haematocrit)
- Lipid panel
- Liver function tests (AST, ALT, GGT)
- Prostate PSA (if > 50 or risk factors)
- Blood pressure
- Heart rhythm (ECG) if risk factors
At 4–6 weeks:
- Haematocrit (most likely to be problematic early)
- Symptoms review
At 12 weeks:
- Full blood count
- Total and free testosterone (dose adjustment if needed)
- Lipid panel
- Liver function
Ongoing (every 6–12 months):
- Haematocrit
- Testosterone (total and free)
- Oestradiol
- Lipid panel
- Blood pressure
- Prostate PSA (if indicated)
- Symptoms review
Additional:
- Sleep study if risk factors for sleep apnoea or symptoms worsen
The Honest Bottom Line
TRT is safe for most men when properly dosed and monitored. Real side effects exist, but they're largely manageable:
- Acne: Common, usually improves after 2–3 months, responsive to standard treatments.
- Polycythaemia: Most important side effect to monitor. Manageable with dose adjustment or phlebotomy.
- Testicular atrophy: Inevitable without HCG, but reversible if HCG is used or treatment is stopped.
- Fertility suppression: Important if you want biological children; managed with HCG.
- Cardiovascular risk: Minimal in screened men; significant in men with existing disease.
- Mood changes: Usually positive; negative changes usually indicate oestradiol imbalance or excessive dose.
The key: TRT requires proper oversight. A prescription with no follow-up is irresponsible. Find a clinic or doctor who actually monitors, adjusts protocol based on results, and takes side effects seriously.
With proper management, TRT is an effective, safe treatment for men with genuine low testosterone.