At what time are testosterone levels naturally the lowest?

When Testosterone Levels Are Naturally Lowest

Testosterone levels are naturally at their lowest point in the evening, typically around 7:00 PM, with levels rising during sleep and reaching their peak in the early morning between 7:00-10:00 AM. 1

Diurnal Variation of Testosterone

Testosterone follows a distinct circadian rhythm in men, characterized by:

• Morning peak: Highest levels occur between 7:00-10:00 AM, forming a "plateau" of elevated testosterone 1
• Evening nadir: Lowest levels occur around 7:00 PM 1
• Nighttime rise: Levels begin to increase during sleep 1, 2

This diurnal pattern is particularly pronounced in younger men. Research shows that men under 30 years experience the most significant daily fluctuations in testosterone levels, with the magnitude of variation decreasing with age 3.

Age-Related Considerations

The diurnal variation in testosterone levels is affected by age:

• Younger men (under 30): Experience more dramatic daily fluctuations 3
• Middle-aged men: Show moderate diurnal variation
• Older men: Display less pronounced differences between morning and afternoon levels 3, 4

This age-related change in testosterone rhythm is important to consider when evaluating for potential testosterone deficiency. While older men show less diurnal variation, they also tend to have lower overall testosterone levels, with total and free testosterone declining while sex hormone-binding globulin (SHBG) rises with age 4.

Clinical Implications

The natural diurnal variation of testosterone has important implications for clinical practice:

• Timing of measurements: The Endocrine Society and American College of Clinical Endocrinologists recommend morning hormone measurements for testosterone due to this diurnal variation 5
• Diagnostic thresholds: Age-specific reference ranges should be considered when evaluating testosterone levels, as young men (20-44 years) have different normative values than older men 6
• Sleep impact: Research shows that sleep quantity and quality significantly affect morning testosterone levels, particularly in older men 2

Common Pitfalls to Avoid

1. Incorrect sampling time: Measuring testosterone in the evening could lead to falsely low readings due to natural diurnal variation
2. Using age-inappropriate reference ranges: Young men should be evaluated using age-specific cutoffs rather than the general 300 ng/dL threshold 6
3. Ignoring sleep factors: Poor sleep can significantly lower morning testosterone levels, especially in older men 2
4. Single measurements: Due to day-to-day variability, multiple morning measurements provide more reliable assessment

Understanding the natural diurnal pattern of testosterone is essential for proper diagnosis and management of potential testosterone deficiency, ensuring that low readings are not simply a reflection of normal physiological variation.