Testosterone replacement therapy

Key points about testosterone replacement therapy (TRT)

  • Testosterone replacement therapy (TRT) is a prescription medicine used to treat low testosterone levels in some men with significant symptoms.
  • In some men with low testosterone, TRT can improve your mood, energy, wellbeing, libido (sex drive) and sexual function.
  • Find out how to use TRT safely and possible side effects.
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TRT is a medicine to treat the symptoms of testosterone deficiency (TD or low testosterone levels), a condition called hypogonadism. If your body doesn't make enough testosterone, you may benefit from having supplemental testosterone – also called testosterone replacement therapy. 

TRT is testosterone given as a medicine prescribed by a doctor to treat the symptoms of low testosterone levels. Examples of testosterone preparations include:

  • injections, eg, Depo-Testosterone, Sustanon 250, Reandron
  • a patch applied to the skin – Androderm
  • gel applied to the skin – Testogel. Read more about testosterone gel

TRT is not for everyone. You need to have blood tests, a full discussion with your doctor, and ongoing monitoring to see if it’s right for you. Read more about low testosterone levels.

Testosterone patches (Androderm) are being discontinued in Aotearoa New Zealand

It's likely that from August 2024, it will be difficult to source Androderm patches. Teva, the pharmaceutical company that supplies Androderm patches, is discontinuing this product. There are no replacement testosterone patches but testosterone injection and testosterone gel are available. Talk to your healthcare provider about the best alternative for you. Read more about the testosterone patches (Androderm) discontinuation(external link).

Gender affirming hormone therapy

GAHT refers to the hormone therapy (oestrogen or testosterone), used by some transgender and non-binary people to help align their body with their gender. Learn more about testosterone based GAHT.

TRT is a medicine prescribed by your doctor to treat testosterone deficiency (low levels of testosterone) to reach physiologic (natural) levels of the hormone in your blood.

Performance-enhancing steroids (sometimes commonly called anabolic steroids) are unregulated products that contain testosterone or chemicals that act like testosterone. They're sometimes used by bodybuilders and athletes. They contain these substances in higher doses and they're often combined with other chemicals that boost the overall muscle-building (anabolic) effect.

Long-term use of performance-enhancing steroids can cause harmful effects.

  • Injection: Testosterone injections are given into the muscle, usually in your buttocks, thigh, or upper arm. Injections are typically given every 2 to 4 weeks. The TRT injection can cause swings in testosterone levels in some people. This can lead to fluctuations in mood and sexual behaviour, as well as breast tenderness and other symptoms. You’ll need to have follow-up blood tests. Make sure you have these on time, to check the dose is right for you. Before injecting TRT, warm the medicine to body temperature to reduce pain at the injection site. It’s important that Reandron is injected slowly into a large muscle. 

  • Patch: Testosterone patches are applied to the skin daily, typically on the upper arm or abdomen. The patch should be applied to a different area each day to avoid skin irritation. You should avoid showering, swimming and sexual activity for 4 hours after putting on the patch. Skin irritation is common at the site of the patch.

  • Gel: You rub gels into your skin daily. They're convenient to use, but you have to be careful that no one comes into contact with the treated area for several hours after you've applied it. 

TRT is used to treat testosterone deficiency (TD or low testosterone) in some men. A low testosterone level by itself doesn't need treatment. TRT can have side effects, and the long-term risks and benefits aren't well known. 

Only men with symptoms of low testosterone and blood tests that confirm this should consider testosterone replacement. Men with testosterone levels in the bottom of the normal range, but still normal, aren't usually treated with TRT. Read more about low testosterone levels. Since testosterone levels normally fall as men get older, the risks of testosterone replacement may outweigh the benefits for older men with levels that are slowly falling over time. 

TRT may be considered for people:

  • born with testosterone deficiency due to diseases such as Klinefelter syndrome.
  • with sex organs that don't develop as usual.
  • with damaged testicles.

The benefits of testosterone treatment can include improved mood, eg, feeling less depressed, and improved libido (sexual interest). TRT can also change your body composition, eg, give you more muscle mass and less abdominal fat.

You'll need routine health exams to see that your testosterone level has changed and stays normal.

If erectile dysfunction is the only symptom of low testosterone, TRT is unlikely to be used. A PDE5 inhibitor (eg, sildenafil) is preferred, after other causes have been addressed. Read more about erectile dysfunction and PDE5 inhibitors.

TRT shouldn't be used if you have:

  • known or suspected breast or prostate cancer
  • polycythemia (high levels of red blood cells)
  • liver tumours
  • high calcium levels (hypercalcaemia)
  • severe heart or kidney disease
  • untreated obstructive sleep apnoea.

Effects on fertility:

As a result of using testosterone replacement, your natural production of testosterone may be reduced. This may also lead to a reduction in sperm production which can affect your fertility. If you're considering having children in the future you should discuss this with your doctor prior to starting treatment.


Other possible risks of testosterone treatment include:

  • a high red blood cell count, which can cause heart problems and blood clots
  • in some cases, a higher risk of heart attacks and stroke
  • acne and oily skin
  • worsening of male pattern baldness
  • an increase in prostate size
  • unmasking or worsening of a pre-existing prostate cancer (but it doesn’t cause prostate cancer)
  • skin irritation of the area of the patch
  • pulmonary oil microemoblism (spread of oil droplets into your lungs) for Reandron injection 
  • testicular (ball) shrinkage on rare occasions with injections.

The following lifestyle changes can help you maintain a healthy level of testosterone:

  • lose weight if you are overweight
  • keep active and exercise regularly (but not vigorously)
  • get enough sleep (at least 7 hours per night)
  • don't drink too much alcohol
  • reduce stress. 

Do not use unregulated products that contain testosterone or chemicals that act like testosterone.

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr Art Nahill, Consultant General Physician and Clinical Educator.

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