Is 400 ng/dL low?
Usually no — 400 ng/dL is within many reference ranges. Symptoms at that level deserve a look at sleep, mood, medications, and free T, not an automatic TRT start.
EDUCATION CENTER
What Testosterone Level Is Considered Low? Understanding Testosterone Test Results
How clinicians interpret total and free testosterone.
What testosterone level is considered low?
Many guidelines discuss total testosterone below about 300 ng/dL (10.4 nmol/L) as a commonly used threshold, measured on a reliable morning assay and confirmed on repeat testing. Your lab’s reference interval may differ slightly.
A result of 305 ng/dL is not “healthy” and 295 ng/dL is not automatically “disease.” Clinicians interpret the number with symptoms, free testosterone, SHBG, and whether the sample was drawn under the right conditions.
What is the difference between total and free testosterone?
Total testosterone is bound plus unbound hormone. Most circulating testosterone is bound to SHBG or albumin. Free testosterone is the unbound fraction that tissues can more readily use.
Obesity, thyroid disease, and aging change SHBG. That is why two men with the same total T can feel very different, and why free T is often added when total T is borderline.
How should a testosterone blood test be drawn?
Draw in the morning, ideally before 10 a.m., while you are reasonably well (not mid-acute illness). Repeat a low or borderline value before making a treatment decision. Fasting is not always required; follow the order your clinician wrote.
After you start TRT, draw timing depends on the product: troughs before an injection, or a specified window after gel application.
FAQs
Can my level change day to day?
Yes. Sleep, training, illness, and time of day all move the number. That is why repeat morning testing is standard.
References
Related guides
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