The Reality Behind the Possible Side Effects

For men with genuine testosterone deficiency, testosterone replacement therapy (TRT) can make a real difference. At H3 Health, we regularly see men reporting improvements in energy, motivation, libido, body composition, and overall wellbeing once testosterone levels are improved.

Most men tolerate TRT very well. But some do notice side effects, particularly in the early stages, after dose increases, or if levels drift too high. Usually these are manageable, and reversible with relatively simple adjustments.

Fertility deserves a specific mention first, particularly for younger men. TRT suppresses the brain's signalling to the testes, which can reduce sperm production. This doesn't need to be a barrier to treatment — if maintaining fertility is important, medications such as HCG or clomiphene are often used alongside TRT. They work differently, but both help maintain the signalling to the testes that keeps sperm production going during treatment.

One of the most common side effects of TRT is a rise in haematocrit — the proportion of red blood cells in the blood. Testosterone stimulates red blood cell production, and in some men this causes the blood to become thicker over time. Most men feel no symptoms at all, though occasionally men notice headaches, facial flushing, or breathlessness. If haematocrit rises significantly, there may be an increased risk of blood clots, which is why we monitor it closely. If levels do creep up, it's usually straightforward to manage through adjusting the testosterone dose or frequency of injection. Giving blood or venesection can also help to lower levels if other measures don’t work.

Oestrogen is something men worry about more than they probably need to. It's natural for some testosterone to convert to oestrogen, and a slight increase is completely normal and in the right amounts healthy. If levels rise too high, the most typical symptom is breast tissue tenderness or swelling — or gynaecomastia, where a small lump can be felt behind the nipple — which is the main thing men tend to worry about. But it's usually quite straightforward to manage through changes in testosterone dose or frequency, and lifestyle measures like weight loss and cutting back on alcohol. Medications like aromatase inhibitors or 'oestrogen blockers' are rarely needed.

Oilier skin and acne can be fairly common, particularly in the first few months or after dose changes, and usually in men with a past history of acne. This is because testosterone increases sebaceous gland activity. Simple measures like ensuring testosterone levels aren't running too high, or using salicylic acid-based cleansers, usually help. More significant flare-ups may need topical or oral antibiotics from your GP.

Finally, mood changes are usually a change for the better. Most report improvements in confidence, mental clarity, concentration and overall wellbeing once deficiency is treated. However, if testosterone levels run too high — which can in turn drive oestrogen up — some men feel more irritable or emotionally reactive. This can easily be sorted with some fine-tuning of testosterone dose or frequency.

The key point

For the right man on the right treatment, benefits consistently outweigh the risks — not just better blood test results, but feeling more like themselves again. Most men tolerate TRT very well, and when issues do arise, they're picked up through routine monitoring and straightforward to adjust. At H3 Health, that's exactly how we approach it: sensible dosing, regular blood tests, and adjustments over time where needed.

Common Myths and Questions About TRT Side Effects

Does TRT increase the risk of prostate cancer?

Current evidence is genuinely reassuring here. TRT is not thought to cause prostate cancer in men without pre-existing disease. PSA is always monitored routinely — not because TRT is expected to cause cancer, but because testosterone can produce a modest PSA rise, and monitoring helps ensure nothing important is missed.

Does TRT cause hair loss?

Hair loss is probably one of the most common concerns men ask about before starting TRT. Testosterone can convert to a hormone called DHT, which in genetically susceptible men may accelerate male pattern hair loss. However, current thinking supports the 'saturation model' — where receptors in hair follicles appear to become fully saturated at relatively low testosterone levels. Put simply, if you're not losing hair at your current testosterone levels, raising them is unlikely to suddenly cause it. And if you're already losing hair, TRT may accelerate things slightly, but the underlying cause is your genetics rather than the treatment itself. For most men it's much less of an issue than they fear.

Are side effects common on TRT?

Most men tolerate TRT well. Skin changes such as oiliness or acne are probably the most reported side effect. More significant problems — such as substantially raised haematocrit or symptomatic gynaecomastia — are less common and are usually picked up through routine monitoring before they become an issue.

Want to learn more about TRT? Then get in contact with one of our specialists today.

References

• Da Ros CT et al. J Sex Med. 2025. PMID: 39908204
• Kraft J, Freiman A. CMAJ. 2011;183–E435.
• Kanakis GA et al. Andrology. 2019;7:778–793.
• Kacker R et al. J Sex Med. 2012;9:1681–1696.
• Bhasin S et al. J Clin Endocrinol Metab. 2010;95:2536–2559.
• Kohn TP et al. J Urol. 2024;211:285–293.
• Rivero MJ et al. J Urol. 2023;210:162–170.
• Madhusoodanan V et al. Int Braz J Urol. 2019;45:1008–1012.
• Da Ros CT et al. Int Braz J Urol. 2022;48:850–856.