Free vs. Total Testosterone: Which One Matters More?
Testosterone is one of the most important hormones for muscle growth, metabolism, energy levels, and sexual function. But when you get a testosterone test, you may notice two different types of measurements: free testosterone and total testosterone.
Many people wonder, which one matters more for health and performance? This article breaks down the key differences between free and total testosterone, how they affect your body, and which test you should focus on.
Understanding the Two Types of Testosterone
Testosterone exists in two primary forms in the bloodstream:
1. Total Testosterone (TT)
✅ Includes all testosterone in the body
✅ Most commonly measured in blood tests
✅ Bound to proteins like SHBG (sex hormone-binding globulin) and albumin
Total testosterone represents the overall amount of testosterone circulating in your system. However, much of it is inactive because it’s bound to proteins that prevent it from interacting with cells.
2. Free Testosterone (FT)
✅ Unbound and available for use
✅ The "active" testosterone that influences muscles, libido, and energy
✅ Makes up about 1-2% of total testosterone
Free testosterone is what actually enters cells and triggers biological effects. Even if your total testosterone is normal, low free testosterone can cause symptoms of testosterone deficiency.
Normal Levels: How Free & Total Testosterone Are Measured
Testosterone levels are typically measured in nanograms per deciliter (ng/dL) for total testosterone and picograms per milliliter (pg/mL) for free testosterone.
Normal Ranges for Total & Free Testosterone
| Age Group | Total Testosterone (ng/dL) | Free Testosterone (pg/mL) |
|---|---|---|
| 20-30 years | 300-1,000 | 9-26 |
| 30-40 years | 270-950 | 8-22 |
| 40-50 years | 250-900 | 7-20 |
| 50+ years | 200-750 | 5-18 |
🔹 Free testosterone is typically 1-2% of total testosterone.
If your total testosterone is in the normal range but your free testosterone is low, you may still experience symptoms of low T.
Which Is More Important: Free or Total Testosterone?
Total Testosterone Is the Standard Test
- Doctors typically check total testosterone first because it gives an overall picture of hormone production.
- However, total testosterone doesn’t tell the whole story—most of it is bound and inactive.
Free Testosterone Is the Best Indicator of Symptoms
- Free testosterone is what actually works in the body.
- If you have low free testosterone, you may experience symptoms like:
🚨 Fatigue
🚨 Low libido
🚨 Muscle loss
🚨 Depression
Why SHBG (Sex Hormone-Binding Globulin) Matters
SHBG is a protein that binds to testosterone, making it unavailable for use. High SHBG can lower free testosterone, even if total testosterone looks normal.
🔹 If you have symptoms of low testosterone but normal total testosterone, check SHBG and free testosterone.
When Should You Get a Free Testosterone Test?
A free testosterone test is recommended if:
✔️ You have symptoms of low testosterone, but total testosterone is normal.
✔️ You have high SHBG levels, which may lower free testosterone.
✔️ You are considering testosterone therapy (TRT) and want to ensure your active levels are low.
📌 Best Time to Test: Morning (7-10 AM) for the most accurate results.
What Causes Low Free Testosterone?
Several factors can reduce free testosterone levels:
1. High SHBG Levels
🔹 SHBG binds to testosterone, making it inactive.
🔹 Common in aging, liver disease, and high estrogen levels.
2. Obesity & Insulin Resistance
🔹 Excess body fat increases estrogen, reducing free testosterone availability.
3. Chronic Stress & High Cortisol
🔹 High cortisol (stress hormone) suppresses testosterone production [¹].
4. Nutrient Deficiencies
🔹 Low zinc, vitamin D, or magnesium can impact free testosterone levels [²].
How to Increase Free Testosterone Naturally
If your free testosterone is low, these lifestyle changes can help:
🔥 Lift Weights & Strength Train – Increases free testosterone production.
🥑 Eat Healthy Fats & Protein – Supports testosterone synthesis.
😴 Get More Sleep – 7-9 hours per night boosts testosterone naturally.
🚫 Reduce Stress – Lower cortisol through meditation, exercise, and relaxation.
☀️ Get More Vitamin D – Sun exposure and supplements help maintain testosterone levels.
For severe cases, testosterone replacement therapy (TRT) may be an option, but only under medical supervision.
Final Thoughts: Which Test Should You Focus On?
| Factor | Total Testosterone | Free Testosterone |
|---|---|---|
| What It Measures | All testosterone in blood | Active, usable testosterone |
| Better for Diagnosing Low T? | ❌ Sometimes misleading | ✅ More accurate for symptoms |
| Affected by SHBG? | ✅ Yes | ❌ No |
| Most Doctors Test? | ✅ Yes | ⚠️ Sometimes |
🔹 Free testosterone is the most important for how you feel and function. If you have symptoms of low T, ask for both free and total testosterone tests.
Footnotes & Citations
- Tsigos, C., et al. “The Role of Cortisol in Testosterone Suppression.” Annals of the New York Academy of Sciences, 2016. Available here
- Holick, M.F., et al. “Vitamin D & Testosterone: A Connection?” The Journal of Clinical Endocrinology & Metabolism, 2012. Available here
- The Endocrine Society. “Testosterone Deficiency and Hormone Testing Guidelines.” Journal of Clinical Endocrinology & Metabolism, 2019. Available here
