Testagen is a lab-made four-amino-acid peptide promoted to support male hormone output, fertility, and healthy aging. Human evidence is one small study without a placebo, in men treated for prostate inflammation; those adding Testagen showed higher testosterone and fewer prostate symptoms. No study has measured sperm or aging. No side effects have been recorded, but no one has systematically looked; product quality is the most concrete concern. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Total testosterone | 600–900 ng/dL | Main claimed target |
| Free testosterone | About 135–225 pg/mL | Active hormone fraction |
| LH | 2–8 IU/L | Shows whether pituitary drive changes |
| FSH | 1.5–8 IU/L | Marker of sperm-production drive |
| SHBG | 20–50 nmol/L | Affects free testosterone |
| Estradiol | 20–30 pg/mL | Estrogen balance in men |
| TSH | 0.5–2.5 mIU/L | Detects thyroid-axis shifts seen in birds |
| Free T4 | 1.0–1.5 ng/dL | Confirms thyroid output |
| PSA | Below 1.0 ng/mL, stable over time | Prostate safety |
| Semen analysis | Concentration ≥ 16 million/mL, progressive motility ≥ 30% | Direct fertility outcome (when fertility is the goal) |
| CBC | Hemoglobin 14–16 g/dL; normal white cells and platelets | General safety |
| CMP | ALT below 25 U/L; eGFR above 90 mL/min/1.73 m² | Liver and kidney safety |
Cadence: Baseline before a first course (morning, fasting); hormone and thyroid panel 4–6 weeks after starting, at the end of each course, then every 6–12 months while courses continue; PSA after each course in men over 45; blood count and chemistry annually; semen analysis repeated after about 74 days.