Safety is, rightly, the first concern most men raise when they consider testosterone replacement therapy. You’ve probably encountered alarming headlines linking TRT to heart attacks, strokes, and prostate cancer. You may also have read enthusiastic claims that TRT is perfectly safe and has no meaningful risks. Neither extreme tells the whole story.
The evidence on TRT safety has evolved significantly over the past decade, and the picture is far more reassuring than the sensationalised headlines suggest, provided treatment is prescribed appropriately, dosed correctly, and monitored properly. But “reassuring” is not the same as “risk-free,” and any honest discussion of TRT must address both what the evidence supports and where uncertainties remain.
This article examines the safety evidence for long-term TRT, addresses the most common concerns head-on, and explains what proper monitoring looks like. If you’re trying to decide whether TRT is right for you, this is the information you need.
The Cardiovascular Question: What We Now Know
For years, the biggest safety concern around TRT was cardiovascular risk. This fear was fuelled by two widely reported studies published in 2013 and 2014 that suggested TRT might increase the risk of heart attacks and strokes. These studies generated enormous media attention and led to regulatory warnings from the FDA in the United States.
However, both studies had significant methodological limitations. They were observational (not randomised controlled trials), had design flaws that were widely criticised by the endocrinology community, and their findings were inconsistent with the broader body of evidence.
The TRAVERSE Trial: A Landmark Study
The question was definitively addressed by the TRAVERSE trial, the largest and most rigorous randomised controlled trial of TRT ever conducted. Published in the New England Journal of Medicine in 2023, the study followed over 5,200 men aged 45-80 with hypogonadism and pre-existing or high risk of cardiovascular disease for an average of 33 months.
The headline finding: TRT did not increase the risk of major adverse cardiovascular events (heart attack, stroke, or cardiovascular death) compared to placebo. The incidence was essentially the same in both groups. This was a study specifically designed to detect cardiovascular harm if it existed, in a population at elevated cardiovascular risk, and it found none.
This doesn’t mean TRT is cardiovascular-protective, and the study wasn’t designed to show that. But it does put to rest the fear that appropriately dosed TRT is a significant cardiovascular danger for most men. The TRAVERSE trial has fundamentally shifted the medical consensus on this question.
It’s worth noting that the study used testosterone gel at doses designed to achieve normal physiological levels. The findings may not apply to supraphysiological doses or anabolic steroid abuse, which carry well-documented cardiovascular risks.
Blood Pressure and Lipids
TRT can have modest effects on cardiovascular risk factors. Some studies show small improvements in insulin sensitivity and reductions in visceral fat, both of which are cardioprotective. Others show small reductions in HDL cholesterol (the “good” cholesterol), which could theoretically increase risk. The net cardiovascular effect appears to be neutral for most men at therapeutic doses, which is consistent with the TRAVERSE findings.
Regular monitoring of blood pressure, lipid profiles, and metabolic markers remains important as part of comprehensive TRT management.
Prostate Health: Separating Fact from Fear
The belief that testosterone causes prostate cancer is one of the most persistent myths in medicine, and it has prevented countless men from receiving treatment they genuinely need. Let’s examine what the evidence actually shows.
Where the Fear Came From
The concern traces back to the 1940s, when Charles Huggins demonstrated that castrating men with advanced prostate cancer slowed the disease’s progression. He later received a Nobel Prize for this work. The logical inference, that if removing testosterone slows prostate cancer, then adding testosterone must cause it, seemed reasonable at the time but has since been shown to be an oversimplification.
What the Evidence Shows
Multiple large-scale studies and meta-analyses conducted over the past two decades have found no increased risk of prostate cancer in men receiving TRT. The prostate cancer sub-study within the TRAVERSE trial found no significant difference in prostate cancer incidence between the testosterone and placebo groups.
The current understanding, articulated in the “saturation model” proposed by Abraham Morgentaler, is that prostate tissue has a finite capacity to respond to testosterone. Once androgen receptors are saturated (which occurs at relatively low testosterone levels), additional testosterone does not further stimulate prostate growth. This explains why men with high-normal testosterone don’t have higher prostate cancer rates than men with low-normal levels.
That said, TRT is still contraindicated in men with known, untreated prostate cancer. If you have active prostate cancer, testosterone could potentially fuel its growth. This is why PSA screening before and during TRT is essential, not because TRT causes cancer, but because it’s prudent to ensure no existing cancer is present before starting treatment.
Men who have been successfully treated for localised prostate cancer may, in some cases, be candidates for TRT after a suitable surveillance period and with careful monitoring. This is a specialist decision that should be made in consultation with both an endocrinologist and a urologist.
Polycythaemia: A Real Risk That’s Manageable
If there’s one safety concern with TRT that deserves genuine attention, it’s polycythaemia: an excessive increase in red blood cells. Testosterone stimulates erythropoiesis (red blood cell production), and in some men, this can push haematocrit levels above the safe range, typically above 0.54 (54%).
Elevated haematocrit increases blood viscosity, which raises the risk of thromboembolic events such as deep vein thrombosis, pulmonary embolism, and stroke. This risk is real, but it is entirely manageable with proper monitoring.
The protocol is straightforward:
- Haematocrit should be checked before starting TRT and at regular intervals (typically every 3-6 months)
- If haematocrit rises above 0.52-0.54, the TRT dose should be reduced
- Blood donation (venesection) can be used to bring levels down if needed
- In rare cases where haematocrit cannot be controlled, TRT may need to be discontinued
Men who are already at risk for polycythaemia (such as those with sleep apnoea or chronic lung disease) need especially careful monitoring. The NHS guidance on polycythaemia outlines the condition and its management.
The key point: polycythaemia on TRT is a monitoring issue, not a reason to avoid treatment. It becomes dangerous only when it goes undetected, which is why unsupervised TRT (buying testosterone without medical oversight) is genuinely risky.
Sleep Apnoea
TRT can worsen obstructive sleep apnoea (OSA) in some men, or unmask previously undiagnosed OSA. The mechanism isn’t fully understood but may relate to changes in upper airway soft tissue or central respiratory drive. Men who snore heavily, who are obese, or who have been told they stop breathing during sleep should be screened for sleep apnoea before starting TRT.
If you already have diagnosed OSA, TRT isn’t necessarily contraindicated, but your sleep apnoea should be adequately treated (typically with CPAP therapy) before and during testosterone treatment. Untreated severe OSA is a contraindication to starting TRT.
Liver Health
Oral testosterone preparations (17-alpha alkylated formulations) were historically associated with liver toxicity, including rare cases of liver tumours. However, these formulations are not used in modern TRT practice in the UK. The injectable, gel, and patch formulations used today do not pass through the liver in the same way and have not been associated with significant liver toxicity.
Liver function tests are still included in routine monitoring as a precaution, but liver damage from modern TRT formulations is not a significant concern.
Mental Health Considerations
Most men experience improved mood on TRT, but a small minority may experience mood changes including increased irritability or emotional instability, particularly during the early stages of treatment or if doses are too high. These effects are generally dose-dependent and resolve with dose adjustment.
Men with a history of psychiatric conditions should discuss this with their prescribing clinician. TRT is not contraindicated in men with depression or anxiety, and may in fact improve these conditions when they’re related to testosterone deficiency, but monitoring for mood changes is good practice.
When TRT Is NOT Safe
There are clear contraindications to TRT that any responsible clinician will screen for:
- Active or untreated prostate cancer: Testosterone could stimulate growth of existing prostate cancer cells
- Male breast cancer: Extremely rare but a clear contraindication
- Uncontrolled polycythaemia: If haematocrit is already elevated, adding testosterone would worsen it
- Severe untreated sleep apnoea: TRT can worsen this potentially life-threatening condition
- Uncontrolled heart failure: Fluid retention from TRT could exacerbate severe heart failure
- Desire for near-term fertility: TRT suppresses sperm production (not a safety issue per se, but an important clinical consideration)
- Elevated PSA without urological evaluation: An unexplained raised PSA needs investigation before TRT is started
These contraindications underscore why proper medical evaluation is essential before starting TRT. A thorough pre-treatment assessment, including blood work, medical history, and sometimes additional investigations, protects you from receiving treatment that could be harmful in your specific situation.
The Importance of Medical Supervision
The safety profile of TRT is fundamentally different depending on whether it’s medically supervised or self-administered. Much of the concern about testosterone safety comes from the world of unsupervised use, where men obtain testosterone without prescription, use excessive doses, combine it with other substances, and skip blood monitoring entirely.
Under medical supervision:
- Your baseline health is thoroughly assessed before treatment begins
- Doses are titrated to achieve physiological levels, not supraphysiological ones
- Blood tests catch emerging issues (polycythaemia, PSA changes, lipid shifts) before they become problems
- Side effects are managed proactively through dose adjustment
- Your overall health is monitored alongside your testosterone levels
Without medical supervision, none of these safeguards exist. This is where the genuine dangers lie, not with TRT itself, but with TRT without oversight.
What Proper Monitoring Looks Like
If you’re on TRT or considering it, here’s what a comprehensive monitoring protocol should include:
Before starting TRT:
- Two morning blood tests confirming low testosterone
- Full blood count (including haematocrit)
- PSA
- Liver function tests
- Lipid profile
- HbA1c or fasting glucose
- LH, FSH (to determine whether hypogonadism is primary or secondary)
- Oestradiol, SHBG, prolactin
- Thyroid function
- Assessment for sleep apnoea symptoms
- Digital rectal examination (in men over 40, depending on clinical judgement)
During treatment (every 3-6 months initially, then 6-12 months once stable):
- Total and free testosterone (to confirm therapeutic levels)
- Full blood count with haematocrit
- PSA
- Oestradiol
- Liver function
- Symptom review and dose adjustment as needed
Any provider who prescribes TRT without this level of monitoring is not providing safe care. At Evernu, comprehensive blood monitoring is a core part of our testosterone treatment protocol, because safety is not optional.
The Bottom Line on TRT Safety
The evidence paints a clear picture:
- Cardiovascular risk: Not increased at physiological doses, as demonstrated by the TRAVERSE trial
- Prostate cancer: No increased risk in men without existing cancer
- Polycythaemia: A real risk that is manageable with monitoring
- Liver toxicity: Not a concern with modern formulations
- Overall: TRT has a favourable safety profile when prescribed appropriately and monitored properly
The risks of TRT are not zero, but they are well-characterised and manageable. For men with genuine testosterone deficiency, the risks of not treating, including metabolic syndrome, osteoporosis, depression, and diminished quality of life, are often greater than the risks of treatment.
Frequently Asked Questions
Does TRT increase the risk of heart attack or stroke?
The largest randomised controlled trial on this question, the TRAVERSE trial published in the New England Journal of Medicine, found no increased risk of major cardiovascular events in men on TRT compared to placebo. This study specifically enrolled men at high cardiovascular risk, making it a robust test of the hypothesis. Earlier observational studies that suggested cardiovascular risk have been widely criticised for methodological limitations. At physiological replacement doses with proper monitoring, TRT does not appear to increase cardiovascular risk.
Can TRT cause prostate cancer?
Current evidence does not support a link between TRT and increased prostate cancer risk in men without existing cancer. Multiple large studies and the TRAVERSE trial have found no increased incidence. However, TRT is contraindicated in men with known, untreated prostate cancer. PSA testing before and during TRT is standard practice to ensure early detection of any prostate issues, not because TRT causes cancer, but as a general health screening measure for men in the relevant age group.
What are the most common side effects of long-term TRT?
The most frequently reported side effects include increased haematocrit (which requires monitoring), acne or oily skin, fluid retention, and testicular atrophy. Some men experience oestrogen-related effects if testosterone converts to oestradiol at higher rates, including water retention or mood changes. Most side effects are dose-dependent and resolve with adjustments. Serious adverse effects are uncommon with properly supervised treatment at physiological doses.
How often do I need blood tests on TRT?
Blood tests are typically recommended at 6-12 weeks after starting or adjusting your dose, then every 3-6 months during the first year, and every 6-12 months once your levels are stable. Key markers include testosterone levels, full blood count (especially haematocrit), PSA, oestradiol, and liver function. More frequent testing may be needed if any values are outside the target range. Skipping blood tests on TRT is not advisable, as it removes the safety net that makes the treatment manageable.
Is it safe to take TRT if I have high blood pressure?
High blood pressure alone is not a contraindication to TRT, and some studies suggest TRT may modestly improve metabolic parameters that contribute to hypertension. However, TRT can cause fluid retention in some men, which could temporarily raise blood pressure. If you have hypertension, it should be adequately controlled before starting TRT, and blood pressure should be monitored as part of your ongoing care. Your prescribing clinician should assess your overall cardiovascular risk profile before making a recommendation.
Making a Safe Choice
If you’re considering TRT in the UK, whether in England, Scotland, Wales, or Northern Ireland, the most important safety measure isn’t a specific medication or dose. It’s choosing a provider who takes safety seriously: one who conducts thorough pre-treatment assessments, insists on regular monitoring, and adjusts your treatment based on evidence rather than guesswork.
Evernu is a RQIA-regulated healthcare provider offering medically supervised testosterone replacement therapy with comprehensive monitoring protocols. We believe that safe TRT is well-monitored TRT, and we build that principle into every aspect of our service.
If you’ve been hesitating because of safety concerns, we hope this article has given you a clearer, evidence-based perspective. The conversation about TRT safety has moved on from the headlines of a decade ago. The question isn’t whether TRT is safe. It’s whether it’s right for you, and that’s a question best answered with your doctor.
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any new treatment.
Reviewed by the Evernu medical team. Last updated: March 2026.
