Testosterone is the main male sex hormone, and levels naturally decline gradually with age. True low testosterone (hypogonadism) combines symptoms with confirmed low blood levels. Common symptoms include low libido, fewer morning erections, erectile problems, tiredness, depressed mood, irritability, reduced muscle mass and strength, increased belly fat, and sometimes hot flushes or reduced body hair.
The tricky part is that these symptoms overlap heavily with stress, poor sleep, depression, thyroid problems, obesity, and other conditions, so symptoms alone are not enough to diagnose it. Testosterone is normally measured in a morning blood sample, often repeated, since levels vary through the day and drop temporarily during illness.
See a doctor if you have several of these symptoms. Avoid self-diagnosing from online quizzes or buying testosterone or boosters online, as inappropriate treatment carries risks including infertility. A clinician can test properly and look for treatable underlying causes.