How to prepare for the ‘Total testosterone’ test: rules for taking it
Total testosterone is one of the most frequently ordered hormone tests in men, and at the same time one of the most ‘capricious’. The hormone level changes over the course of the day, drops after eating, sleep deprivation or illness, and the result also depends on the laboratory's method. Our editorial team has gathered the preparation rules recommended by clinical guidelines, so that the figure on the form reflects the real state rather than a random coincidence of circumstances.
Why proper preparation matters
Total testosterone is the combined amount of the hormone in blood serum: the portion bound to sex hormone-binding globulin (SHBG), the portion bound to albumin, and a small free fraction. This is precisely the indicator that is the first step in diagnosing hypogonadism, assessing sexual development, monitoring replacement therapy and examining women with suspected hyperandrogenism.
The problem is that testosterone is not a constant value. Its secretion follows a circadian rhythm and responds to glucose intake, lack of sleep, acute illness and intense physical exertion. Fluctuations over a few hours can be so noticeable that the same man may get a result ‘within the normal range’ on one day and ‘below the reference range’ on another.
The Endocrine Society clinical guideline on testosterone therapy (Bhasin et al., 2018) directly requires confirming a diagnosis of low testosterone with at least two morning fasting tests. This requirement did not appear by chance: in cohort studies a significant proportion of men with a low first result had a normal level on repeat sampling.
Misdiagnosis has real consequences. A person with ‘falsely low’ testosterone may be groundlessly prescribed hormone therapy, which suppresses their own secretion and fertility. And conversely, improper preparation can mask a genuine deficiency. That is why a few simple rules before the blood draw are worth attention.
Below we look specifically at preparation for the test. Interpretation of the result, causes of deficiency and approaches to treatment are separate topics that a doctor should assess taking symptoms into account.
Blood draw timing and the circadian rhythm
In young and adult men, testosterone levels are highest in the morning and gradually decline toward evening. A study by Brambilla and colleagues (2009), which analysed the daily fluctuations of hormones in men of different ages, showed that evening values in younger men are noticeably lower than morning ones, and with age the amplitude of the circadian rhythm decreases but does not disappear completely.
That is precisely why the reference intervals of most laboratories and the harmonised norms (Travison et al., 2017) are based on morning samples. If you have blood drawn at 4 p.m. and compare it with a morning norm, you may get a result that falsely indicates a deficiency.
A practical rule supported by the guidelines: blood is drawn in the morning, roughly between 7:00 and 10:00–11:00. For people who work night shifts, ‘morning’ shifts according to their sleep cycle, so this circumstance should be reported to the doctor — otherwise the result may be interpreted incorrectly.
If you are tracking trends, take repeat tests at approximately the same time of day. A difference of a few hours between two draws can produce a greater discrepancy than a real change in hormonal status over a month.
In women, the circadian rhythm of testosterone is less pronounced, but for comparability of results laboratories and doctors likewise recommend a morning draw, and with a regular cycle — coordinating the date with the cycle phase, usually the early follicular one.
Food, sleep, exercise and alcohol
One of the least obvious but well-documented causes of a falsely low result is food intake. In a study by Caronia and colleagues (2013), an oral glucose load reduced testosterone concentration in men by about a quarter, and in some of those examined the level dropped below the threshold used to diagnose hypogonadism. That is why the test is taken fasting: after 8–12 hours without food, only water is allowed.
Sleep is the second important factor. In a small but telling study by Leproult and Van Cauter (2011), a week of restricting sleep to five hours a night lowered daytime testosterone in healthy young men by about 10–15%. So a test after a sleepless night, a night shift or a flight across several time zones is better postponed.
Intense exercise the day before can also distort the picture. Short-term changes in testosterone after exertion depend on the type and duration of the work, while prolonged exhausting loads and an energy deficit can lower the hormone. The editorial team advises against intense training in the 24 hours before the test and against scheduling a blood draw immediately after competition.
- last meal at least 8 hours before, only water in the morning;
- a full night's sleep beforehand, without night shifts or unusual ‘sleep loss’;
- no heavy training in the 24 hours before the draw;
- no alcohol for at least a day;
- 15–20 minutes of rest before the draw, without smoking.
Acute illness — a cold with fever, a flare-up of a chronic disease, surgery or trauma — temporarily lowers testosterone. The Endocrine Society guideline advises against assessing gonadal function during an acute illness. If you have recently been ill, it is better to wait a few weeks after recovery.
Medications, supplements and biotin
Many drugs directly affect testosterone levels. These include opioids, glucocorticoids, some anticonvulsants, agents that affect 5-alpha-reductase or aromatase, as well as any androgens, anabolic steroids and hormonal agents. The list of medications you take must be given to the doctor — you must not discontinue prescribed therapy on your own before the test.
Biotin (vitamin B7) is a separate story. It is often included in high doses in ‘hair, skin and nail’ complexes. Many immunoassays use a ‘streptavidin–biotin’ system, and an excess of biotin in the blood can distort the result both upward and downward. In 2017 the FDA officially warned about the risk of such false results.
| Factor | Possible effect on the result | What to do |
|---|---|---|
| Biotin in high doses | False elevation or reduction depending on the test system | Inform the doctor; usually advised to skip intake for at least 1–3 days, the exact interval to be confirmed with the laboratory |
| Opioids, glucocorticoids | Reduced testosterone | Do not discontinue on your own, note it on the referral |
| Androgens, AS, hormone therapy | The result reflects exogenous hormone, not the body's own secretion | Be sure to inform the doctor |
| Acute illness | Temporary reduction | Postpone the test for a few weeks after recovery |
For people receiving testosterone replacement therapy, the timing of the blood draw relative to the last dose of the drug is determined by the doctor, because interpretation depends directly on it. Comparing results taken on different days of the interval between doses is incorrect.
Ordinary dietary supplements such as vitamin D, zinc or magnesium usually do not distort the test itself, but if you have started taking them recently, it is worth noting this. That way the doctor can correctly compare changes over time.
Laboratory methods and repeat testing
Total testosterone is measured by two main groups of methods: automated immunoassays and liquid chromatography with tandem mass spectrometry (LC-MS/MS). The Endocrine Society position statement (Rosner et al., 2007) drew attention to the fact that immunoassays are less accurate in the range of low concentrations — in women, children and men with pronounced deficiency.
For men with normal and moderately reduced values, modern certified immunoassays that have undergone standardisation under the CDC programme usually provide acceptable accuracy. However, the results of different laboratories may differ, so for monitoring over time it is better to choose one laboratory and not change it without need.
Pay attention to the units of measurement. In Ukraine nmol/L is most often used, in the USA — ng/dL. To convert, a value in ng/dL is divided by 28,84 to obtain nmol/L. Comparing ‘bare’ figures without units is a common mistake when reading foreign articles and forums.
If the first result is low or borderline low, it must be repeated: this approach is enshrined in the guidelines. It is advisable to repeat the draw under similar conditions — in the morning, fasting, after normal sleep — and together with total testosterone, LH, FSH, SHBG and prolactin are often measured to understand the level of the disorder.
The harmonised reference interval for men aged 19–39 without obesity, proposed by Travison and colleagues (2017), is approximately 264–916 ng/dL (about 9,2–31,8 nmol/L) by standardised methods. However, you should ultimately rely on the interval of your laboratory indicated on the form.
Editorial conclusions
Total testosterone is a simple test with complex biology. The result depends on the hour of the draw, food intake, sleep, illness, medications and even vitamin complexes containing biotin.
The basic rules are simple: morning, fasting, after your usual sleep, without training or alcohol the day before, and with the doctor informed of all medications and supplements. A low result must be confirmed by repeat testing, rather than drawing conclusions from a single form.
Interpretation of the test always combines the figures with symptoms and other indicators, so the decision on any treatment is made by a doctor — an endocrinologist or andrologist.
The editorial team also recommends reading our materials on preparing for the free testosterone, SHBG and luteinizing hormone tests — together they give a much fuller picture than a single indicator.
References
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
- Rosner W, Auchus RJ, Azziz R, et al. Position statement: utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. J Clin Endocrinol Metab. 2007;92(2):405–413.
- Brambilla DJ, Matsumoto AM, Araujo AB, McKinlay JB. 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.
- 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.
- Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA. 2011;305(21):2173–2174.
- Travison TG, Vesper HW, Orwoll E, et al. Harmonized reference ranges for circulating testosterone levels in men of four cohort studies in the United States and Europe. J Clin Endocrinol Metab. 2017;102(4):1161–1173.
- U.S. Food and Drug Administration. The FDA warns that biotin may interfere with lab tests: FDA safety communication. 2017.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
