Low testosterone can be diagnosed by an assessment of symptoms and a blood test to measure testosterone levels. The symptom most associated with low testosterone is reduced sex drive (low libido), however your doctor will ask about a range of symptoms.

How to diagnose hypogonadism in men?

The symptoms of hypogonadism may vary from individual to individual. In late-onset hypogonadism many symptoms resemble those of aging and as a consequence this condition is often undiagnosed. Various diagnostic procedures are available to confirm hypogonadism in a patient who presents with symptoms or signs of testosterone deficiency. These include:

Laboratory tests

Determination of testosterone values

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Repeat measurement of morning total testosterone (when levels of serum testosterone can be expected to be higher because of the diurnal rhythm of testosterone) using a reliable assay is recommended by international professional societies in the field as the most widely accepted parameter to establish the presence of hypogonadism in combination with consistent symptoms and signs. In some men, determination of free or bioavailable testosterone may be appropriate.1,2

Measurement of testosterone levels in the diagnosis of hypogonadism

Calculate the bioactive
testosterone circulating in plasma

Values for normal testosterone ranges vary among laboratories depending on the commercial assay employed, and local values should be consulted when a diagnosis of hypogonadism is considered. There is no generally accepted lower limit of normal.

Testosterone Concentration:
12-35 nmol/L
Free Testosterone:
250 pmol/L (72 pg/mL)

A morning testosterone concentration in the blood of 12-35 nmol/L or free testosterone levels above 250 pmol/L (72 pg/mL) can be considered normal.There is general agreement that no testosterone treatment is required.

Testosterone Concentration:
< 12-35 nmol/L
Free Testosterone:
180 pmol/L (52 pg/mL)

The European Association of Urology (EAU), International Society for the Study of the Aging Male (ISSAM), International Society of Andrology (ISA), European Academy of Andrology (EAA) and American Society of Andrology (ASA) suggest that serum total testosterone levels below 8 nmol/L (231 ng/dL) or free testosterone below 180 pmol/L (52 pg/mL) require testosterone replacement therapy.

In addition, concentrations of the pituitary hormones can be measured. They provide information as to whether the testosterone deficiency is due to disorders of testicular function or of the hypothalamic-pituitary system.


Since symptoms of testosterone deficiency become manifest between 8 and 12 nmol/L (231–346 ng/dL), trials (3– >6 months) of treatment can be considered in men with a clinical picture of testosterone deficiency and borderline testosterone levels when alternative causes of these symptoms have been excluded.1,2


Please consult guidelines relevant to your country of practice as country-specific differences in the diagnosis and treatment of hypogonadism exist.

Supplementary tests

Supplementary tests, like a bone density test for suspected osteoporosis or tests to exclude other diseases that may explain the symptomatology, may be necessary. The physician’s experience and, in some cases, the observation of clear clinical benefits after the initiation of testosterone therapy may provide confirmation of a diagnosis of hypogonadism.

Treatment options

Treatment of low testosterone is quite straightforward. Once the decision has been made to increase testosterone levels, low testosterone can be replaced by using one of a number of treatment options. All of these treatment options require a doctor’s prescription. An ideal preparation of testosterone will bring testosterone levels back into the normal range to reverse the symptoms of low testosterone. It will also be safe and offer a convenient dosing schedule and means of administration.

Several months of treatment may be required before changes are apparent. The general recommendations are to raise the blood testosterone level only into the middle of the normal physiological range. As testosterone therapy is long term, it is important that it is convenient, safe and effective.

Testosterone effects tool

Visualisation of the time course for onset of the many beneficial testosterone effects.


The benefits of testosterone replacement

The benefits of testosterone replacement on sexual function, fat and lean body mass and bone density in men with low testosterone are clear. The potential benefits of testosterone replacement in reducing the risk of cardiovascular disease, metabolic syndrome and diabetes are still being investigated.


  • Prevents anaemia


  • Controls sexual function (sex drive, erectile function, orgasm)
  • Reduces lower urinary tract symptoms (LUTS)
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  • Improves mood, energy, wellbeing and quality of life
  • Prevents depression

Physical symptoms

  • Increases muscle mass
  • Increases strength
  • Decreases overall body fat mass
  • Decreases belly (visceral) fat mass
  • Increases bone mineral density

Health and well-being – quality of life

Improvements in signs and symptoms of low testosterone, such as libido, sexual, physical and mental functioning and mood, can be expected over time and will show you that the treatment is working.

Body composition

Testosterone replacement in men with low testosterone increases lean body mass and strength and decreases fat mass.


Testosterone therapy may also have metabolic benefits in men with diabetes and/or metabolic syndrome. Men with diabetes have been shown to have substantially lower testosterone levels than men in the general population, yet low testosterone in many remains undiagnosed and untreated. It is not yet fully known whether diabetes is a cause or a consequence of low testosterone.


Low testosterone can lead to thinning of the bones (osteoporosis) and men with hip fractures tend to have low testosterone. Testosterone replacement increases bone density.

If low testosterone occurs during adulthood, you can make some lifestyle and dietary changes to help prevent osteoporosis. Regular exercise and adequate amounts of calcium and vitamin D help to maintain bone strength and are important to reduce the risk of osteoporosis.

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  • Bhasin S, Cunningham GR, Hayes FJ, et al. Testosterone therapy in adult men with androgen deficiency syndromes: an endocrine society clinical practice guideline. J Clin Endocrinol Metab 2006; 91(6): 1995-2010. Return to content
  • Wang, C., E. Nieschlag, R. Swerdloff, et al. Investigation, treatment and monitoring of late-onset hypogonadism in males: ISA, ISSAM, EAU, EAA and ASA recommendations. Eur J Endocrinol 2008, 159(5): 507-514. Return to content