Testosterone is a steroid hormone that is produced by the testes in men, and the ovaries in women.
Having high testosterone levels has been linked with many benefits, it can improve sex drive, improve mood (but cannot treat clinical depression), increase muscle mass, and lower body fat.
Testosterone has such a positive effect on performance that it has become popular for gym-goers (especially those interested in bodybuilding) to inject themselves with testosterone illegally.
In an article for the Medical Journal of Australia , David Handelsman talks about testosterone as a therapeutic drug and the ironic situation that it suffers from both overuse and underuse.
He claims that testosterone is overused and overestimated by many young and older men who are seduced by the possible anti-aging and muscle building effects, whilst also being underused by doctors to treat low testosterone levels in men.
This article will give you a quick look at some of the reported symptoms of low testosterone levels. But please be aware that whilst displaying these symptoms could signify low testosterone levels, they could also be signifying other issues.
If you are worried, then please check with a doctor before doing anything drastic.
Even if you aren't affected by any of the following symptoms, there are many benefits to naturally increasing your testosterone levels which we will briefly look into at the end of this article. But first, here are some of the most common symptoms of low testosterone levels.
1. Low Sex Drive
Testosterone has an effect on sexual function in men, whilst high testosterone levels can increase a man's sex drive, low testosterone can have the opposite effect.
Other symptoms can include erectile dysfunction and a lack of interest in sex . Some experts believe that increasing testosterone levels in older men could increase their sex drive, as men will start to produce less testosterone naturally from middle-age onwards .
Some researchers believe that low testosterone when combined with high cortisol (which can be a symptom of overtraining) can cause fatigue .
This is not noticeable with every athlete, but there is enough evidence to support the belief that low testosterone levels can be associated with fatigue.
So if you are constantly feeling exhausted then low testosterone could be responsible.
Another possibility is that a person with low testosterone can be suffering with anemia, a study by Ferrucci et al (2006) concluded that men and women with low testosterone levels have a higher risk of having anemia (which can cause weariness or fatigue) .
There is a difference between depression and being clinically depressed.
In science depression can simply mean a lowering of mood, so that's what you should be thinking of during this point.
There has been many studies on the links between testosterone and mood, and a study by Barrett-Conner, Muhlen & Kritz-Silverstein found that testosterone treatment might improve depressed mood in men with low levels of testosterone .
4. Lower Muscle Mass
Men with lower testosterone would find it harder to build muscle than men with high testosterone. This is due to the influence of testosterone on muscle protein synthesis .
If you are finding it difficult to build muscle naturally then low testosterone levels might be the reason why.
It is for this reason that injectable testosterone has become so popular within gyms, and why steroids are the most used drug in competitive bodybuilding.
5. Increased Body Fat
As with muscle mass, high testosterone levels tend to lower body fat whilst low testosterone levels tends to increase fat storage . Again, this is another reason why gym goers and bodybuilders use steroids.
For this reason, there is a link between obesity and low testosterone levels and also Type 2 Diabetes sufferers tend to have lower testosterone . There is also a link with cardiovascualr disease risk and low testosterone.
So how can you naturally increase Testosterone?
You can eat more meat, as vegetarians consistently appear to have lower testosterone levels than meat eaters .
You could increase dietary fat, as this appears to have a positive relationship with high testosterone levels . Lift heavy weights, as this will produce more testosterone  (particularly free weight exercises). Also improving your sleep will boost testosterone .
For more testosterone boosting tips you may want to check out our natural testosterone boosting article.
There you have it, symptoms to look out for when you're concerned about your testosterone levels and a quick guide to how to improve your testosterone levels naturally.
As mentioned at the beginning of this article however getting a doctor to check you out is the best way to discover whether your testosterone levels are low or not.
And finally, whatever you do don't decide to start injecting yourself with testosterone, this is really a dangerous thing to do and if you do require it your doctor will offer it to you.
 Handelsman, D. 2006. Testosterone: use, misuse and abuse. The Medical Journal of Australia 185(8): 436-439
 Isidori, A., Giannetta, E., Gianfrilli, D., Greco, E., Vincenzo, B., Aversa, A., Isidori, A., Fabbri, A., Lenzi, A. 2005. Effects of Testosterone on sexual function in men: results of a meta-analysis. Clinical Endocrinology 63(4): 381-394
 Handelsman, D., Liu, P. 2005. Andropause: invention, prevention, rejuvenation. Trends in Endocrinology & Metabolism 16(2): 39-45
 Budgett, R. 1998. Fatigue and underperformance in athletes: the overtraining syndrome. British Journal of Sports Medicine 32: 107-110
 Ferrucci, L., Maggio, M., Bandinelli, S., Basaria, S., Lauretani, F., Ble, A., Valenti, G., Ershler, W., Guralnik, J., Longo, D. 2006. Low Testosterone levels and the risk of Anemia in older men and women. Arch Intern Med. 166(13): 1380-1388
 Barrett-Conner, E., Von Muhlen, D., Kritz-Silverstein, D. 1999. Bioavailable testosterone and depressed mood in older men: The Rancho Bernardo Story. The Journal of Clinical Endocrinology & Metabolism 84(2): 573-7
 Griggs, R., Kingston, W., Jozefowicz, R., Herr, B., Forbes, G., Halliday, D. 1989. Effect of Testosterone on muscle mass and muscle protein synthesis. Journal of Applied Physiology 66(1): 498-503
 Snyder, P., Peachey, H., Hannoush, P., Berlin, J., Loh, L., Lenrow, D., Holmes, J., Dlewati, A., Santanna, J., Rosen, C., Strom, B. 1999. Effect of Testosterone Treatment on Body Composition and Muscle Strength in Men Over 65 Years of Age. The Journal of Clinical Endocrinology & Metabolism 84(8): 2647-2653
 Wang, C., Jackson, G., Jones, H., Matsumoto, A., Nehra, A., Perelman, M., Swerdloff, R., Traish, A., Zitzmann, M., Cunningham, G. 2011. Low Testosterone associated with obesity and the metabolic syndrome contributes to sexual dysfunction and cardiovascular disease risk in men with type 2 diabetes. American Diabetes Association 34(7): 1669-1675
 Hill, P., Wynder, E. 1979. Effect of a vegetarian diet and dexamethasone on plasma prolactin, testosterone and dehydroepiandrosterone in men and women. Cancer Letters 7(5): 273-282
 Hamalainen, E., Aldercreutz, H., Puska, P., Pietinen, P. 1984. Diet and serum sex hormones in healthy men. Journal of Steroid Biochemistry 20(1): 459-464
 Shaner, A., Vingren, J., Hatfield, D., Budnar, R., Duplanty, A., Hill, D. 2014. The Acute Hormonal response to free weight and machine weight resistance exercise. Journal of Strength & Conditioning Research 28(4): 1032-40
 Goh, V. Tong, T. 2010, Sleep, sex steroid hormones, sexual activities, and ageing in Asian men. Journal of Andology 31(2): 131-7