In short
A higher red blood cell count, lower sperm production, acne and fluid retention are the main ones. Most are found on routine blood tests and managed by adjusting the dose.
On this page
The main side effects of TRT are a higher red blood cell count, lower sperm production, acne or oily skin, and fluid retention. Most are picked up by routine blood tests and managed by adjusting the dose. Serious problems are uncommon at normal doses with proper monitoring.
Common side effects
| Side effect | What happens | What’s done about it |
|---|---|---|
| Higher red blood cell count | Testosterone stimulates red cell production, which thickens the blood | Checked by blood test. The dose is lowered or the form changed if it climbs. |
| Lower sperm production | Your own testosterone and sperm production switch off | Discussed before starting. See TRT and fertility. |
| Acne and oily skin | More common early on and in younger men | Usually settles. Skin treatments or a dose change help. |
| Smaller testicles | They’re doing less work | Expected, and reverses if treatment stops. |
| Breast tenderness or swelling | Some testosterone converts to oestrogen | Dose review. |
| Fluid retention | Ankle swelling | Matters more with heart, kidney or liver disease. |
Less common, more serious
- Sleep apnoea can get worse.
- Prostate. Treatment doesn’t appear to cause prostate cancer, but it can make an existing one grow, so PSA is checked before and during treatment.
- Heart and blood vessels. In a large trial of more than 5,000 men, heart attacks and strokes were no more common with testosterone than with placebo. Irregular heartbeat, kidney injury and blood clots in the lung were slightly more common.
Form-specific effects
- Injections. Soreness at the site, and with the long-acting injection a brief coughing fit straight after is possible, which is why it’s given slowly in a clinic.
- Gels and creams. Skin irritation, and transfer to partners or children through skin contact. Wash your hands and cover the area.
What gets monitored
Before starting, in the first few months and then at least yearly: testosterone level, full blood count and PSA, plus a check on symptoms, sleep and mood.
When to get help
Call 000 for chest pain, sudden breathlessness, or weakness on one side of the body. See a doctor promptly for a swollen, painful calf, a racing or irregular heartbeat, or trouble passing urine.
Next step: talk to a GP
Request an appointment and we’ll be in touch to arrange a time. A consultation doesn’t guarantee a prescription.
References
- Lincoff AM, et al. Cardiovascular safety of testosterone-replacement therapy (TRAVERSE). New England Journal of Medicine. 2023.
- Yeap BB, et al. Endocrine Society of Australia position statement on male hypogonadism (part 2). Medical Journal of Australia. 2016.
- Healthy Male: Testosterone replacement therapy
This guide is general information, not medical advice. It doesn’t replace a consultation with a doctor who knows your history. In an emergency, call 000.