What is Testosterone?
Testosterone is a steroid hormone produced primarily in the testes in men and ovaries in women, with additional production from the adrenal glands in both sexes. It exists in the bloodstream in two main forms: total testosterone (the complete amount circulating) and free testosterone (the biologically active fraction not bound to carrier proteins). Most testosterone is bound to SHBG (sex hormone-binding globulin) and albumin , only the free fraction can enter cells and exert hormonal effects.
Testosterone baseline is essential context before any GH or hormonal peptide research. Low testosterone symptoms , fatigue, poor recovery, reduced libido, mood changes, body composition decline , overlap significantly with GH deficiency symptoms. Knowing testosterone levels before beginning a GH secretagogue protocol helps distinguish which system is driving symptoms and whether a hormonal approach, a GH approach, or both are most relevant to the research question.
What do the numbers mean?
Women: Total 15–70 ng/dL · Free 1–5 pg/mL
Women: Total 15–70 ng/dL
Lab reference ranges vary by laboratory, age, sex, and testing method. Always interpret your results with your healthcare provider , do not self-diagnose based on these ranges.
Why this marker matters before peptide research.
Testosterone directly influences the GH axis , low testosterone impairs GH pulsatility and reduces IGF-1 levels, meaning a GH secretagogue protocol in a significantly hypogonadal individual may produce blunted results. Research also shows testosterone and GH have synergistic effects on body composition , understanding both before a protocol provides more complete biological context for interpreting outcomes.
For reproductive and sexual health peptide research (PT-141, Kisspeptin-10), testosterone is the primary baseline marker alongside estradiol, LH, FSH, and SHBG. Understanding whether low libido or sexual dysfunction has a hormonal root versus a central nervous system driver informs which peptide research context is most relevant. PT-141 acts centrally on melanocortin receptors , its potential utility is different from that of testosterone optimization.
SHBG (sex hormone-binding globulin) is an important companion marker when total testosterone is ordered. High SHBG can render total testosterone functionally low , a man with total testosterone of 600 ng/dL and very high SHBG may have functionally low free testosterone with clinical symptoms of hypogonadism. Ordering both total and free testosterone, plus SHBG, provides a complete picture of hormonal bioavailability.
How to get this test.
Where to order
Standard blood draw at any major lab , LabCorp, Quest Diagnostics, or through your physician. Direct-to-consumer options are widely available through services like Ulta Lab Tests and LabCorp OnDemand without a doctor's order.
How to prepare
Draw between 7–10 AM , testosterone follows a circadian rhythm and peaks in the morning. Afternoon draws can show values 20–30% lower than morning levels. Fasting is not required but consistent morning timing is critical for reproducibility across draws.
What to ask for
"Total Testosterone and Free Testosterone" , request both simultaneously. Adding SHBG provides important context for bioavailability. Some panels bundle all three. Specify morning draw when ordering through a physician or lab.