Free testosterone (serum/plasma, mass concentration)

Why is this test important?

Free testosterone is important because it reflects your body’s biologically active hormone levels. Unlike total testosterone, which includes both free and bound forms, free testosterone is the portion that directly influences reproductive and metabolic functions. This test can help diagnose conditions like low testosterone, polycystic ovary syndrome (PCOS), or other hormonal imbalances.

What does it measure?

This test measures the unbound (free) testosterone in your blood plasma or serum. Free testosterone is the form of testosterone that circulates freely in your bloodstream and is available to bind with receptors in your body’s tissues. It’s determined using advanced laboratory techniques that separate free testosterone from protein-bound forms.

When might you need this test?

You may need a free testosterone test if you have symptoms of hormonal imbalances, such as low libido, fatigue, or changes in mood and energy levels. It may also be ordered during fertility evaluations, before hormone therapy, or if you have conditions like hypogonadism (low testosterone) or hyperandrogenism (high testosterone). Your healthcare provider will determine if this test is necessary based on your medical history and symptoms.

What can affect results?

Several factors can influence free testosterone levels, including medications (such as steroids or birth control), certain health conditions (like obesity or thyroid disorders), and lifestyle choices like smoking or alcohol use. Stress, diet, and exercise can also play a role. If you’re taking medications or have recent changes in health, let your provider know to ensure accurate results.