Testosterone replacement therapy is an effective treatment for men with clinically low testosterone, but like all medical treatments, it carries the potential for side effects. Being informed about what to expect helps you recognise issues early and work with your clinic to manage them effectively. The good news is that most side effects are manageable and often preventable with proper monitoring and dose adjustment.
Common Side Effects
The following side effects are relatively common, particularly in the early stages of treatment or when doses are too high. Most resolve with proper management.
Elevated Haematocrit (Polycythaemia)
TRT stimulates the production of red blood cells, which can increase haematocrit levels. While a modest increase is normal and expected, levels above 54% raise the risk of blood clots, stroke, and cardiovascular events. This is the most important safety marker to monitor during TRT.
Management:
- Regular blood tests to monitor haematocrit levels
- Dose reduction if levels rise above safe thresholds
- Therapeutic phlebotomy (blood donation or medical blood removal) if needed
- Staying well hydrated
- More frequent, smaller doses can help keep levels stable
Oestrogen-Related Side Effects
Testosterone is partially converted to oestradiol (a form of oestrogen) by the enzyme aromatase. When testosterone doses are high or body fat levels are elevated, this conversion can increase, leading to:
- Water retention: Bloating and puffiness, particularly in the face and extremities
- Gynaecomastia: Tender or enlarged breast tissue
- Mood changes: Increased emotional sensitivity or irritability
Management:
- Optimising body composition through diet and exercise reduces aromatase activity
- Dose adjustment to find the right balance
- More frequent injection schedules to avoid large testosterone peaks
- An aromatase inhibitor such as anastrozole may be prescribed in some cases, though this is used cautiously
Acne and Oily Skin
Testosterone stimulates sebaceous gland activity, which can lead to increased oil production and acne. This is more common in men who had acne-prone skin in their youth. It tends to be most noticeable in the first few months of treatment.
Management:
- Consistent skincare routine with salicylic acid or benzoyl peroxide
- Dose adjustment if acne is severe
- Ensuring doses are not excessively high
- In severe cases, dermatological referral may be appropriate
Injection Site Reactions
For men using injectable testosterone, mild soreness, redness, or swelling at the injection site is common, especially early on.
Management:
- Rotate injection sites regularly
- Use proper injection technique
- Allow the oil to reach room temperature before injecting
- Consider subcutaneous injection, which some men find less irritating
Less Common Side Effects
Sleep Apnoea
TRT may worsen pre-existing obstructive sleep apnoea or contribute to its development in susceptible individuals. Symptoms include loud snoring, gasping during sleep, and excessive daytime sleepiness. If you notice these symptoms, inform your doctor promptly.
Testicular Atrophy
When exogenous testosterone is introduced, the body reduces its own production, which can lead to the testes shrinking in size. This is a cosmetic concern for some men and can also affect fertility.
Management:
- HCG (Human Chorionic Gonadotropin) can be prescribed alongside TRT to maintain testicular size and function
- This is particularly important for men who wish to preserve fertility
Read our article on TRT and fertility for more information.
Changes in Lipid Profile
TRT can affect cholesterol levels, potentially lowering HDL (good cholesterol) and raising LDL (bad cholesterol). Regular lipid panel testing helps detect any unfavourable changes early.
Mood Fluctuations
While most men experience improved mood on TRT, some may notice increased irritability or mood swings, particularly if doses are too high or if there are significant peaks and troughs in testosterone levels. Switching to more frequent, smaller doses usually resolves this.
Side Effects That Are NOT Caused by TRT
There are several conditions commonly misattributed to TRT that the evidence does not support:
- Prostate cancer: Current evidence does not show that TRT causes prostate cancer, though monitoring PSA levels is still recommended as a precaution
- Heart attacks: Large-scale studies have not confirmed an increased risk of cardiovascular events with properly managed TRT. In fact, some evidence suggests cardiovascular benefits from restoring normal testosterone levels.
- Liver damage: This concern relates to oral methylated testosterone, which is not used in modern TRT. Injectable and transdermal testosterone do not pose a significant liver risk.
The Importance of Monitoring
The vast majority of TRT side effects are preventable or manageable with proper monitoring. This is why choosing a clinic with thorough blood test protocols is so important. A good clinic will check haematocrit, oestradiol, PSA, liver function, and lipid profiles at regular intervals and adjust your treatment accordingly.
You can compare TRT clinics to find one that prioritises safety and comprehensive monitoring.
Conclusion
TRT side effects are real but generally manageable. The key is proper dosing, regular monitoring, and working with a knowledgeable medical team. Most men on well-managed TRT experience far more benefits than drawbacks. Being informed about potential side effects empowers you to recognise issues early and address them before they become problematic.