What are the most common side effects of TRT?

Possible effects include changes in haematocrit, fluid retention, acne or oily skin, mood changes, fertility suppression, breast tenderness, and effects on prostate markers. Most are detectable on monitoring and many are dose-related.

Will TRT affect my fertility?

Exogenous testosterone usually suppresses the body's own production of testosterone and sperm. Men who want to preserve fertility should discuss alternatives or fertility-preserving strategies before starting TRT.

What is monitored after starting TRT?

Clinicians typically monitor symptoms, testosterone level at the right time relative to dose, haematocrit, PSA where indicated, lipids, and overall wellbeing. The exact schedule depends on the formulation, baseline values, and individual risk factors.

TRT Side Effects

What clinicians monitor on TRT, and why.

Last updated: 1 May 2026

TRT can produce both expected and unwanted effects. Most are detectable on monitoring, many are dose-related, and a small number are reasons to stop or change treatment. This page explains what clinicians watch and why.

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Safety monitoring on testosterone therapy

Haematocrit and bloods

TRT can raise haematocrit. Doctors check full blood count regularly, particularly in the first months of treatment, and adjust the plan if values rise outside acceptable ranges.

Prostate markers

PSA may rise on TRT in the first months. Doctors review baseline and follow-up PSA in age-appropriate men, alongside prostate symptoms, before and during treatment.

Fertility, mood, skin

Common dose-related effects include fertility suppression, acne or oily skin, fluid retention, and mood changes. These are part of routine review and can usually be managed with dose or formulation adjustments.

Why monitoring is part of safe TRT

TRT is a long-term clinical decision, not a one-off prescription. Monitoring is how doctors confirm the right dose, catch unintended effects early, and decide whether treatment should continue, change, or stop. The monitoring schedule depends on the formulation, baseline values, and individual risk factors, but the principle is consistent: treatment that is started should be reviewed.

Effects that are most often monitored

Haematocrit can rise on TRT, particularly with injectable formulations. Doctors watch for this with regular full blood counts and may reduce dose, change formulation, or pause treatment if values exceed safe thresholds.

Prostate-specific antigen (PSA) can rise modestly in the first months of TRT and then plateau. Significant rises or new urinary symptoms are reasons for further review. Baseline PSA and prostate symptom review is standard in age-appropriate men before treatment starts.

Fertility is usually suppressed by exogenous testosterone. Men who want to preserve fertility should discuss this before starting TRT, as alternative or fertility-preserving strategies may be appropriate.

Other effects that can occur include acne, oily skin, fluid retention, mood changes, breast tenderness, sleep changes, and in some men a rise in oestradiol. Most are dose-related and usually respond to dose or formulation adjustments under clinical review.

Cardiovascular risk and TRT

Cardiovascular risk on TRT remains an active area of research. Recent large randomised evidence has been reassuring in appropriately diagnosed men, but TRT is generally avoided after a recent cardiovascular event and used cautiously in men with significant cardiovascular risk factors. A doctor weighs the individual picture: existing risk, alternatives, and what monitoring will look like.

When to stop or pause TRT

Treatment may need to be paused or stopped if haematocrit rises outside safe thresholds, if PSA rises in a way that warrants urological review, if a new contraindication develops, if fertility goals change, or if symptoms do not respond. These decisions are clinical and individual.

What this page is and is not

This page is general information for men in Ireland researching TRT. It does not replace an individual medical consultation, diagnosis, or treatment plan, and it does not promote any specific medication. Care decisions are made by a qualified clinician on a case-by-case basis.

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