Last reviewed: October 2026
Tired, low drive, putting on weight around the middle, not feeling as sharp as you used to? Online ads and social media will often tell you the answer is “low T”. The reality is more complicated. Low testosterone is a real medical condition, but it is less common than marketing suggests, and many of these symptoms have other causes that are worth finding first.
What testosterone does
Testosterone plays a role in sex drive, erections, sperm production, muscle and bone strength, body hair, energy and mood. Levels tend to fall slowly with age, but for most healthy men this fall is small.
The symptoms are real, but they are not specific
Symptoms that can be linked with low testosterone include:
- low sex drive, fewer morning erections, or erection problems
- tiredness and low energy
- low mood or irritability
- loss of muscle and strength, or more body fat
- in more severe or long-standing cases, loss of body hair, smaller testes or thinning bones.
The challenge is that every one of these can also be caused by something else: poor sleep, stress, depression, alcohol, being above a healthy weight, diabetes, heart disease, some medicines, or simply getting older. Feeling tired and flat does not, on its own, mean your testosterone is low.
How low testosterone is properly diagnosed
Leading guidelines, including the US Endocrine Society (2018) and the Endocrine Society of Australia (2016), agree that diagnosis needs both:
- Symptoms and signs consistent with low testosterone, and
- Low testosterone confirmed on blood tests, taken in the morning (when levels are highest), ideally fasting, and repeated on a separate day.
Evidence: strong guideline consensus.
Why the fuss? Testosterone levels go up and down through the day and are lowered by recent illness, poor sleep, a big meal or heavy alcohol. A single afternoon test can be misleadingly low. Other blood tests, such as luteinising hormone (LH) and follicle-stimulating hormone (FSH), help work out why levels are low, which matters for the right next step.
Two quite different situations
Australian experts separate low testosterone into two broad groups.
Pathological hypogonadism. This is caused by a problem with the testes, or with the pituitary gland or brain that controls them. Examples include certain genetic conditions, injury, past chemotherapy or pituitary disorders. Here, testosterone treatment is well established, at any age. Evidence: strong.
Low testosterone linked to other health issues. Much more common. Obesity, type 2 diabetes, sleep apnoea, heavy drinking, chronic illness, and some medicines (such as opioids and steroids) can all lower testosterone without any disease of the testes or pituitary. The Endocrine Society of Australia states that clear evidence for the benefit and safety of testosterone treatment in this group is lacking. Evidence: uncertain.
The good news is that tackling the underlying cause can help. A review of studies found that losing weight was linked with a rise in testosterone, and the more weight lost, the bigger the rise. Evidence: moderate. Treating sleep apnoea, improving sleep, cutting back on alcohol and regular exercise, especially strength training, are worthwhile for overall health regardless.
Fertility: an important warning
This is something many men are not told. Taking testosterone switches off the body’s own sperm production. It can greatly reduce sperm counts, sometimes to zero. This usually recovers after stopping, but recovery can take months or longer and is not guaranteed.
The Endocrine Society recommends that testosterone treatment not be used in men who are planning to have children in the near future. If future fertility matters to you, say so before any treatment is considered. Evidence: strong.
What about the risks?
For years there were concerns about testosterone and heart attacks. A large US trial published in 2023 (TRAVERSE), in men aged 45 to 80 with confirmed low testosterone and heart risk factors, found testosterone treatment did not increase heart attacks or strokes compared with placebo over about three years. However, it did find higher rates of an irregular heart rhythm (atrial fibrillation), blood clots in the lungs and kidney injury. Evidence: strong for that group over that time; long-term effects remain less certain.
Testosterone treatment also needs ongoing monitoring, for example of red blood cell levels, which can rise and thicken the blood.
Reading the marketing with a critical eye
Be cautious of services or ads that:
- suggest most men over 40 need testosterone
- diagnose from a symptom quiz or a single blood test
- do not check why your levels are low
- skip conversations about fertility, side effects and monitoring
- use phrases such as “optimal levels” or “anti-ageing”.
The bottom line
Low testosterone is real, but it should be diagnosed carefully, with symptoms plus repeated morning blood tests, and with a search for the cause. For many men, sleep, weight, alcohol and overall health are the place to start. Treatment can help men with genuine hormone deficiency, but it is not a quick fix for tiredness or ageing, and it has real trade-offs, especially for fertility.
References
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology & Metabolism. 2018;103(5):1715–1744. https://doi.org/10.1210/jc.2018-00229
- Yeap BB, Grossmann M, McLachlan RI, et al. Endocrine Society of Australia position statement on male hypogonadism (part 1): assessment and indications for testosterone therapy. Medical Journal of Australia. 2016;205(4):173–178. https://doi.org/10.5694/mja16.00393
- Yeap BB, Grossmann M, McLachlan RI, et al. Endocrine Society of Australia position statement on male hypogonadism (part 2): treatment and therapeutic considerations. Medical Journal of Australia. 2016;205(5):228–231. https://doi.org/10.5694/mja16.00448
- Corona G, Rastrelli G, Monami M, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. European Journal of Endocrinology. 2013;168(6):829–843. https://doi.org/10.1530/EJE-12-0955
- Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular safety of testosterone-replacement therapy. New England Journal of Medicine. 2023;389(2):107–117. https://doi.org/10.1056/NEJMoa2215025
This article is general information only and is not a substitute for individual medical advice. Talk to your health practitioner about your own situation.