What are normal testosterone levels?

Normal Testosterone Levels in Adult Males

The normal range for testosterone in adult men is 300-800 ng/dL, with the American Urological Association defining levels below 300 ng/dL as the threshold for low testosterone across all adult age groups. 1

Standard Reference Ranges

• Most clinical laboratories report normal testosterone as 300-800 ng/dL for adult men 1
• However, there is significant variability among laboratories, with lower limits ranging from 160-300 ng/dL and upper limits from 726-1,130 ng/dL across different facilities 2
• The 300 ng/dL cutoff is the most widely accepted diagnostic threshold, though this was developed primarily from samples of older men 3, 4

Age-Specific Considerations

Young men (20-44 years) have higher testosterone levels than the standard 300 ng/dL cutoff suggests:

• Men aged 20-24: middle tertile range 409-558 ng/dL, with low testosterone defined as <409 ng/dL 4
• Men aged 25-29: middle tertile range 413-575 ng/dL, with low testosterone defined as <413 ng/dL 4
• Men aged 30-34: middle tertile range 359-498 ng/dL, with low testosterone defined as <359 ng/dL 4
• Men aged 35-39: middle tertile range 352-478 ng/dL, with low testosterone defined as <352 ng/dL 4
• Men aged 40-44: middle tertile range 350-473 ng/dL, with low testosterone defined as <350 ng/dL 4

Older men have age-appropriate lower thresholds:

• Men in their 50s: 2.5th percentile at 216 ng/dL 5
• Men in their 60s: 2.5th percentile at 196 ng/dL 5
• Men in their 70s: 2.5th percentile at 156 ng/dL 5

Critical Measurement Requirements

Proper diagnosis requires specific testing protocols:

• Two separate morning measurements (between 8-10 AM) are mandatory before diagnosing low testosterone 1, 3
• Morning measurements are essential because testosterone levels naturally fluctuate throughout the day, with peak levels occurring in the morning 1
• Fasting morning samples provide the most accurate assessment 1
• Studies show that up to 25% of men receiving testosterone therapy do not meet proper diagnostic criteria 1

Clinical Interpretation Pitfalls

The 300 ng/dL threshold has important limitations:

• Total testosterone between 280-350 ng/dL is not sensitive enough to reliably exclude hypogonadism 6
• Total testosterone must exceed 350-400 ng/dL to reliably predict normal free testosterone 6
• In obese men with low total testosterone, free testosterone measurement is essential because obesity affects sex hormone-binding globulin levels 1
• Only when total testosterone is below 150 ng/dL can you confidently diagnose hypogonadism without additional testing 6

Target Range for Testosterone Replacement Therapy

If treatment is initiated, the goal is the middle tertile of normal:

• Target range: 450-600 ng/dL for men on testosterone replacement therapy 1
• Use minimal dosing necessary to achieve this physiologic range 1
• For men on therapy, maintain trough levels within 300-1,000 ng/dL 1