What are normal total testosterone levels in adult males?

Normal Total Testosterone Levels in Adult Males

Normal total testosterone in adult males is generally defined as 300-800 ng/dL (10.4-27.7 nmol/L), though this range should be adjusted downward for younger men, with age-specific lower limits ranging from 409 ng/dL for men in their 20s to 350 ng/dL for men in their 40s. 1, 2

Standard Reference Range

• The widely accepted normal range is 300-800 ng/dL (10.4-27.7 nmol/L) across most laboratories 1
• The American College of Physicians used 10.4 nmol/L (300 ng/dL) as the threshold for low testosterone in their clinical trials evaluating testosterone treatment 3
• This 300 ng/dL cutoff has been the traditional diagnostic threshold, though emerging evidence suggests it may be too low for younger men 2

Age-Specific Normal Ranges

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

• Men aged 20-24 years: Lower limit 409 ng/dL (middle tertile: 409-558 ng/dL) 2
• Men aged 25-29 years: Lower limit 413 ng/dL (middle tertile: 413-575 ng/dL) 2
• Men aged 30-34 years: Lower limit 359 ng/dL (middle tertile: 359-498 ng/dL) 2
• Men aged 35-39 years: Lower limit 352 ng/dL (middle tertile: 352-478 ng/dL) 2
• Men aged 40-44 years: Lower limit 350 ng/dL (middle tertile: 350-473 ng/dL) 2

For older men, the 2.5th percentile cutoffs decline with age:

• Men in their 40s: 251 ng/dL (8.7 nmol/L) 4
• Men in their 50s: 216 ng/dL (7.5 nmol/L) 4
• Men in their 60s: 196 ng/dL (6.8 nmol/L) 4
• Men in their 70s: 156 ng/dL (5.4 nmol/L) 4

Critical Measurement Requirements

Proper diagnosis requires two separate morning measurements:

• Testosterone levels must be measured in the morning when levels are naturally highest 1
• Two total testosterone measurements on separate occasions are required before diagnosing low testosterone 1
• Both measurements should be conducted in early morning fashion 1
• Samples collected within 4 hours of awakening are preferred 4

Factors Affecting Normal Ranges

Health status significantly impacts what constitutes "normal":

• Chronic disease, high BMI (>29 kg/m²), and certain medications significantly decrease testosterone levels 4
• Smoking tends to increase total testosterone concentrations 4
• Apparently healthy men have significantly higher median testosterone concentrations than unhealthy men at all age points 4
• Men with obesity may have low total testosterone due to low sex hormone-binding globulin but normal free testosterone levels 1

Clinical Pitfalls to Avoid

The 300 ng/dL cutoff is problematic for younger men:

• Using 300 ng/dL as a universal cutoff fails to account for the fact that young men naturally have higher testosterone levels 2
• A 25-year-old man with testosterone of 350 ng/dL would be considered "normal" by traditional standards but falls well below the age-appropriate lower limit of 413 ng/dL 2
• Up to 25% of men receiving testosterone therapy do not meet proper diagnostic criteria for testosterone deficiency 1
• Nearly half of men on testosterone therapy never have their levels rechecked after starting treatment 1

Published normal ranges may be artificially elevated:

• Some studies suggest that published normal ranges are too high because they include unhealthy men in their reference populations 5
• When strict health criteria are applied (excluding chronic disease, obesity, smoking, excessive alcohol), the lower limit of normal may be 3-4 nmol/L (86-115 ng/dL) lower than published ranges 5