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Diagnosing testosterone deficiency (TD)

Starting the conversation with your patients

Testing for TD

TD is confirmed by at least two morning tests of fasting serum testosterone levels on separate occasions in symptomatic men.1

Testosterone circulates in several states with differing androgenic activity. Testosterone may be bound to either sex hormone binding globulin (SHBG) or albumin, and may also circulate freely (unbound).

Testing for TD

Many different assays measuring serum testosterone levels are available. Often, you may be required to calculate free testosterone from investigating albumin, SHBG and total testosterone levels.

Morning test

Morning (7–11am) testosterone blood test on at least 2 occasions1,2

Testosterone levels are subject to diurnal variation and are usually highest in the morning.3 Ideally blood tests will be at least 4 weeks apart and fasting levels obtained as testosterone levels are influenced by insulin (75g glucose has been shown to reduce testosterone levels by 25%).2,4

Reliable method

Use a reliable method and base clinical decisions on published action levels2

The reliability of free testosterone assays based on analog displacement assays has been questioned. Equilibrium dialysis is considered the best diagnostic approach for free testosterone, although it can be more costly than other approaches. Measurement of serum SHBG alongside a reliable measurement of total testosterone allows for calculation of free testosterone level.1

Reference ranges quoted by laboratories represent the normal population.
The action levels recommended by the BSSM refer to men with clinical symptoms of TD. Therefore clinical decisions should be based on published action levels, rather than laboratory reference ranges for low testosterone.2

Testosterone testing


Watch Professor Geoff Hackett from the University of Bedfordshire discuss the Recommended Level of Testosterone at which to Treat Testosterone Deficiency in Men.

Professor Geoff Hackett


Watch Professor Geoff Hackett from the University of Bedfordshire discuss the Tests Needed Before Putting a Man on Testosterone.

Professor Geoff Hackett


  1. Lunenfeld B, Mskhalaya G, Zitzmann M, et al. Recommendations on the diagnosis, treatment and monitoring of hypogonadism in men. Aging Male. 2015;18(1):5–15.
  2. Hackett G, Kirby M, Edwards D, et al. British Society for Sexual Medicine Guidelines on Adult Testosterone Deficiency, With Statements for UK Practice. J Sex Med. 2017;14(12):1504–1523.
  3. Brambilla DJ, Matsumoto AM, Araujo AB, et al. The effect of diurnal variation on clinical measurement of serum testosterone and other sex hormone levels in men. J Clin Endocrinol Metab. 2009;94(3):907–913.
  4. Caronia LM, Dwyer AA, Hayden D, et al. Abrupt decrease in serum testosterone levels after an oral glucose load in men: implications for screening for hypogonadism. Clin Endocrinol (Oxf). 2013;78(2):291–296.

TES/2020/009. April 2021.

Adverse event reporting

Adverse events should be reported. Reporting forms and information can be found at or search for MHRA Yellow Card in the Google Play or Apple App Store. Adverse events should also be reported to Besins Healthcare (UK) Ltd Drug Safety on 0203 862 0920 or Email: