At what time of day should testosterone levels be measured?

From the Guidelines

Testosterone levels should ideally be measured in the morning, between 8 AM and 10 AM, when levels are typically at their highest. This timing is crucial because testosterone follows a circadian rhythm, with peak levels occurring in the early morning and lowest levels in the evening, as noted in a study published in the journal Gastroenterology 1. For accurate diagnosis of testosterone deficiency, most clinical guidelines recommend obtaining at least two morning samples on different days.

Importance of Timing

If you're taking testosterone replacement therapy, blood draws should be timed based on your treatment method: for injections, measure just before your next dose (at the trough level); for topical gels or patches, check levels 2-4 hours after application, as suggested by a study in the Annals of Internal Medicine 1. Fasting isn't strictly necessary for testosterone testing, but consistency in timing helps ensure reliable results for monitoring therapy. Certain factors like illness, poor sleep, alcohol consumption, and intense exercise can temporarily affect testosterone levels, so these should be avoided before testing for the most accurate assessment of your baseline levels.

Clinical Guidelines

The Endocrine Society and American Urological Association guidelines recommend measuring fasting morning concentrations of total testosterone on 2 occasions to diagnose hypogonadism, but vary in their recommendations regarding the threshold at which to categorize a total testosterone level as low, as discussed in a study published in the Annals of Internal Medicine 1. However, a more recent study published in Gastroenterology in 2017 1 emphasizes the importance of measuring morning serum free testosterone, especially in patients with obesity, as it is essential for evaluating low total testosterone clinically.

Monitoring Therapy

After treatment is initiated, patients should be monitored to determine that normal serum testosterone concentrations are being achieved. Testosterone levels should be tested 2 to 3 months after treatment initiation, and/or after any dose change, as recommended by a study in Gastroenterology 1. Once stable levels are confirmed on a given dose, monitoring every 6 to 12 months is typically sufficient. The timing of testosterone measurements will vary depending on the preparation, with levels for patients receiving testosterone injections measured midway between injections, targeting a mid-normal value (500-600 ng/dL), and levels for patients receiving transdermal preparations measured at any time, with the understanding that peak values occur 6 to 8 hours after application of the patch.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Prior to initiating testosterone enanthate injection, confirm the diagnosis of hypogonadism by ensuring that serum testosterone concentrations have been measured in the morning on at least two separate days and that these serum testosterone concentrations are below the normal range The serum testosterone concentrations should be measured in the morning on at least two separate days.

• The measurement should be done before initiating testosterone enanthate injection.
• This is to confirm the diagnosis of hypogonadism 2

From the Research

Testosterone Measurement Timing

• The optimal time for measuring testosterone levels is in the morning, as testosterone levels exhibit a circadian variation with peak levels in the morning 3.
• A study found that testosterone levels measured in blood drawn from 8 to 11 AM differed significantly from those drawn outside this window, with higher levels in the morning 3.
• The study also found that testosterone levels in blood drawn from 2 to 5 PM and 5 to 8 PM were significantly lower than those drawn from 8 to 11 AM, while levels from 11 AM to 2 PM and 8 PM to 8 AM were not significantly different 3.

Implications for Testosterone Measurement

• The findings suggest that it may be possible to expand the blood draw time window for measurement of serum testosterone, but more research is needed to determine the most appropriate blood draw window 3.
• Other studies have focused on the treatment of hypogonadism, including the use of testosterone supplementation therapy and clomiphene citrate, but do not provide direct evidence on the optimal timing for testosterone measurement 4, 5, 6, 7.

Related Research

• Studies have compared the efficacy of different treatments for hypogonadism, including testosterone supplementation therapy and clomiphene citrate, but do not address the specific question of when to measure testosterone levels 4, 5, 6, 7.
• These studies have found that both testosterone supplementation therapy and clomiphene citrate can be effective in increasing testosterone levels and improving symptoms of hypogonadism, but do not provide information on the optimal timing for testosterone measurement 4, 5, 6, 7.