What Is a Testosterone Blood Test?

Testosterone testing measures the primary male sex hormone. It regulates muscle, bone, libido, and mood.

Normal Ranges

• Adult men: 300–1,000 ng/dL
• Peak: age 18–25
• Decline: 1–2%/year after 30
• Hypogonadism: below 300 with symptoms
• Women: 15–70 ng/dL

Free vs Total

• Total = bound + free (most common)
• Free = unbound, biologically active (1–3%)
• High SHBG lowers free T

How to Test

• Morning (7–10 AM)
• Fast if possible
• Confirm with second test
• Check LH/FSH for cause

Low Testosterone Causes

• Aging, obesity
• Chronic disease
• Opioids
• Pituitary disorders