What Labs Do I Need Before Starting Testosterone Therapy?

Why Each Lab Marker Matters

Total testosterone confirms whether levels are clinically low. Free testosterone reveals how much is biologically active — a man can have normal total T but low free T due to elevated SHBG. LH and FSH distinguish primary hypogonadism (testicular failure) from secondary hypogonadism (pituitary signaling issue) — this affects treatment approach. Estradiol baseline is critical because TRT can raise estrogen, causing water retention, mood changes, or gynecomastia. Hematocrit establishes a safety baseline since TRT can increase red blood cell production. PSA screens for prostate concerns before starting therapy.

What Time of Day Should Labs Be Drawn?

Testosterone follows a diurnal rhythm — levels are highest in the morning (7–10 AM) and decline throughout the day. For accurate baseline results, labs should be drawn in the morning, ideally before 10 AM, after a good night's sleep. Avoid heavy exercise, alcohol, or significant stress in the 24 hours before your draw, as these can temporarily suppress testosterone levels.

What Happens After the Labs?

Your provider reviews each marker in the context of your symptoms — not just whether values fall within the standard reference range, but whether they're in the optimal range for your age and goals. For example, a total testosterone of 320 ng/dL is technically 'within range' but may be significantly suboptimal for a 42-year-old experiencing fatigue, low libido, and muscle loss. The goal is optimization, not just normalization.

How Often Are Labs Repeated After Starting TRT?

Follow-up labs are typically drawn 6–8 weeks after starting or adjusting TRT to verify levels are in the therapeutic range and safety markers are stable. Once stable, monitoring labs are done every 3–6 months. Key markers tracked on TRT include total and free testosterone, estradiol, hematocrit, and PSA. Annual lipid panels and metabolic panels are also recommended.

Frequently Asked Questions