Your Available Testosterone
Only 1-3% of your total testosterone is "free"—unbound and available to enter cells. The rest is tied up by SHBG and albumin. You can have normal total testosterone but low FREE testosterone if SHBG is hogging it all. Free T is what actually drives muscle, libido, energy, and mood.
What is Free Testosterone?
Free testosterone is the unbound fraction (~1-3% of total). Calculated free T (from total T, SHBG, albumin) is more reliable than direct assays. Free T better correlates with symptoms than total T.
↑ What High Free Testosterone Means
More active testosterone available than normal. In men: supplementation or low SHBG. In women: PCOS, hirsutism, acne.
Common symptoms:
Women: acne, hirsutism, hair loss, menstrual irregularity · Men: usually from exogenous use (acne, aggression, testicular atrophy)
↓ What Low Free Testosterone Means
Not enough active testosterone reaching cells. Even with normal total T, high SHBG can leave you functionally deficient.
Common symptoms:
Low libido · Fatigue · Muscle loss · Increased body fat · Depression and irritability · Brain fog · Erectile dysfunction (men) · Decreased motivation
Why It Matters
When normal:
Better symptom correlation than total T
Reveals SHBG-related functional deficiency
Important for both sexes
Guides treatment decisions
Risks if abnormal:
Low in men: hypogonadal symptoms despite normal total T
High in women: PCOS, virilization
Direct assays often inaccurate—calculated preferred
What Can Cause Abnormal Levels?
High SHBG (low free T)
50% likelySHBG binds testosterone tightly. High SHBG from aging, liver disease, hyperthyroidism, or estrogen therapy reduces free T.
Low Total Testosterone
45% likelyIf production is low, free fraction drops proportionally.
Obesity
Lowers SHBG (raising free T percentage) but also lowers total T and increases estrogen. Net effect varies.
Insulin Resistance (women)
Insulin lowers SHBG, raising free testosterone—driving PCOS symptoms.
Aging
SHBG rises ~1-2% per year after 40, progressively binding more testosterone.
What You Can Do
Resistance training 3-4x/week (compound lifts)
Impact: Boosts testosterone and improves sensitivity \u00B7 Timeline: 4-8 weeks
Sleep 7-9 hours (testosterone produced during deep sleep)
Impact: 5 hours sleep = 10-15% lower testosterone \u00B7 Timeline: 2-4 weeks
Maintain healthy body fat (15-20% men, 20-30% women)
Impact: Excess fat increases aromatase conversion to estrogen \u00B7 Timeline: 3-6 months
If lifestyle changes aren't enough:
Zinc: 15-30mg daily
Impact: Essential for testosterone synthesis \u00B7 Timeline: 4-8 weeks
Magnesium: 300-400mg daily
Impact: Supports T production and may reduce SHBG binding \u00B7 Timeline: 4-8 weeks
Boron: 6-10mg daily
Impact: Studies show boron lowers SHBG, increasing free T \u00B7 Timeline: 1-2 weeks
Recommended retest: 6-8 weeks after intervention
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