TRT Blood Work: Labs Before and During Testosterone Therapy

TRT blood work has two jobs. Before therapy, it confirms that testosterone is truly low, using fasting morning tests on two separate mornings. During therapy, it watches for side effects, mainly a rise in hematocrit (the share of blood made of red cells) and prostate changes tracked by PSA, a prostate blood marker. Guidelines call for checks at 3 to 6 months, at 12 months, then yearly, and drug labels add blood pressure checks.

Key takeaways

• Diagnosis requires symptoms plus consistently low testosterone on fasting morning samples from two separate mornings.
• The safety baseline is hemoglobin and hematocrit, PSA for men over 40, lipids and blood pressure.
• The Endocrine Society's typical schedule is testosterone and hematocrit at 3 to 6 months, at 12 months, then yearly, though your clinician sets the actual plan.
• In February 2025, the FDA required class-wide labeling changes that add blood pressure warnings to testosterone products, so blood pressure is part of routine monitoring.

Why TRT blood work starts with two morning tests

The first labs confirm a diagnosis. Guidelines call for fasting morning testosterone measured on two separate mornings, and FDA labeling calls for morning measurements on at least two separate days, because a single reading can mislead.

The Endocrine Society recommends diagnosing hypogonadism (low testosterone caused by a problem in the testes or the brain signals that control them) only in men with symptoms and signs of deficiency and unequivocally, consistently low testosterone (Endocrine Society, 2018). FDA labeling says to confirm that testosterone was measured in the morning on at least two separate days, with both results below the normal range. It also notes that safety and efficacy in "age-related hypogonadism" have not been established (testosterone cypionate labeling, 2025).

Testosterone varies across the day and from day to day, and food or glucose can suppress it. That is why the repeat test matters. About 30% of men with an initial low result have a normal level on repeat measurement (Endocrine Society, 2018).

The guideline also calls for accurate assays (the lab methods that measure hormones) for total and free testosterone. Free testosterone is the small fraction not bound to blood proteins. For the symptom side, see our guide to low testosterone symptoms and testing.

Labs before starting TRT: the baseline panel

Once a deficiency is confirmed, a safety baseline follows: hemoglobin and hematocrit, PSA for men over 40, lipids and blood pressure. Later results are compared against these numbers.

Polycythemia means an abnormally high red blood cell count. A second testosterone cypionate label also notes that serum cholesterol may increase during androgen therapy (testosterone cypionate USP label).

The baseline can also surface reasons to pause. The Endocrine Society recommends against testosterone in men planning fertility in the near term, and in men with breast or prostate cancer, a palpable prostate nodule or firm area, or elevated hematocrit. It advises the same for PSA above 4 ng/mL, or above 3 ng/mL in men at high prostate cancer risk, without further urological evaluation (Endocrine Society, 2018). Labeling adds that testosterone may worsen sleep apnea in men with risk factors and may cause azoospermia, meaning no sperm in the semen (testosterone cypionate labeling, 2025). If fertility matters to you, read how TRT affects fertility before your visit.

Hematocrit on TRT: the safety number to understand

Hematocrit is the percentage of blood volume made up of red blood cells. Testosterone can push it up, so it is the most closely watched safety lab on TRT.

FDA labeling lists polycythemia as a warning, with instructions to monitor hematocrit periodically and discontinue if necessary (testosterone cypionate labeling, 2025). In the Endocrine Society guideline's meta-analysis, testosterone was associated with a significantly higher frequency of erythrocytosis, defined there as hematocrit above 54% (relative risk 8.14, 95% confidence interval 1.87 to 35.40) (Endocrine Society, 2018). The analysis has limits. The included trials used transdermal (skin-applied) testosterone for 12 to 52 weeks, and the wide interval means the size of the effect is uncertain.

The AUA guideline gives the clearest thresholds (AUA, 2018):

• Baseline above 50%: clinicians should consider withholding testosterone until the cause is formally investigated.
• On therapy, 54% or higher: this warrants intervention, such as a dose reduction or a temporary stop.

Both figures come from the AUA. The Endocrine Society instead advises against starting in men whose hematocrit is above the lab's upper limit of normal without first discussing erythrocytosis risk and the need for close monitoring (Endocrine Society, 2018).

Labeling also notes that venous thromboembolism, including deep vein thrombosis (a clot in a deep vein) and pulmonary embolism (a clot in the lungs), has been reported with testosterone products (testosterone cypionate labeling, 2025). What to do with a high reading is a clinical decision made with your full history in view.

PSA testing and prostate monitoring on testosterone therapy

PSA is checked before therapy in men over 40 and monitored during treatment, with prostate cancer risk evaluated in the first year.

The AUA says an elevated baseline PSA should be repeated to rule out a spurious result. Two suspicious results warrant more formal evaluation before starting testosterone, possibly reflex testing and biopsy with or without MRI (AUA, 2018).

During therapy, FDA labeling calls for PSA monitoring and for watching men with BPH (benign prostatic hyperplasia, a noncancerous enlargement of the prostate) for worsening symptoms. It lists known or suspected prostate cancer, and breast cancer, as contraindications (testosterone cypionate labeling, 2025). The Endocrine Society's plan includes a prostate cancer risk evaluation during the first year (Endocrine Society, 2018), and a primary-care review notes that the guideline recommends shared decision-making about prostate monitoring (Int J Gen Med, 2022).

How often is blood work done on TRT?

The Endocrine Society recommends checking testosterone and hematocrit 3 to 6 months after starting, depending on the formulation, again at 12 months, and yearly after that. Your clinician sets the actual schedule.

A guideline-comparison review notes that the Endocrine Society and the AUA agree on checking hematocrit 3 to 6 months after starting and annually after that, and on reducing the dose if erythrocytosis develops. It also points out that guidelines vary in other diagnostic and treatment details (Endocrinol Metab, 2020).

Labs are one part of follow-up. The Endocrine Society's plan also covers symptoms, adverse effects and adherence, and it recommends rigorously derived reference ranges for interpreting testosterone results (Endocrine Society, 2018). Ranges differ between labs, so results are read against the reporting lab's range alongside your symptoms and history. One out-of-range value is a reason to talk with your clinician, not a diagnosis.

Questions about when to draw blood belong to your clinician. Worth asking at a visit:

1. Were my two testosterone results fasting and in the morning?
2. What was my baseline hematocrit, and how will it be tracked?
3. Do I need PSA testing at my age?
4. When is my next blood pressure check?

For the bigger picture of evaluation, see how TRT is evaluated.

Blood pressure and the 2025 FDA label change

In February 2025, the FDA required class-wide labeling changes for testosterone products. Cardiovascular boxed-warning language came out, and blood pressure warnings went in.

A boxed warning is the most prominent warning on a drug label. The FDA acted after reviewing the TRAVERSE trial and ambulatory blood pressure monitoring studies, which track blood pressure over a full day and confirmed an increase with all testosterone products. The changes add TRAVERSE results to all testosterone labels, keep the limitation-of-use language for age-related hypogonadism, and require product-specific blood pressure information (FDA, 2025). Current labeling says testosterone can raise blood pressure, which can increase cardiovascular risk over time, and that blood pressure should be measured periodically (testosterone cypionate labeling, 2025).

TRAVERSE, a randomized, placebo-controlled trial in men with symptoms of hypogonadism and existing or high cardiovascular risk, found testosterone noninferior (not meaningfully worse) to placebo for cardiovascular death, nonfatal heart attack and nonfatal stroke, though the testosterone group had higher rates of pulmonary embolism and atrial fibrillation (NEJM, 2023). Investigators stressed that the findings apply to middle-aged and older men with a proper indication, not to men without confirmed hypogonadism.

How access works through New Blue

New Blue's injectable testosterone protocol is a synchronous pathway: a live visit with a licensed clinician plus lab work.

1. Intake and live visit. You share your history and symptoms and meet with a licensed clinician by live visit.
2. Lab work. Labs are part of every New Blue hormone pathway.
3. Clinical review. A licensed clinician reviews your history, symptoms and results and decides whether testosterone therapy is appropriate. Not everyone qualifies. Eligibility depends on your intake and clinical review, and that's how it should work.
4. Fulfillment, if prescribed. A licensed partner pharmacy ships the medication directly to you.
5. Follow-up. Your clinician sets follow-up labs and visits.

The cream and oral testosterone protocols follow the same live-visit-plus-labs model. Availability varies by state, so check state availability. Consultation timing varies by clinician availability. For current pricing, see the injectable testosterone protocol page. If treatment isn't appropriate, refunds follow our refund policy. Care is for adults 21 and older and is not for emergencies.

New Blue is a technology and administrative services platform. Medical services are provided by independent licensed clinicians; medications are dispensed only if prescribed.

Frequently Asked Questions

What blood tests are needed before starting TRT?

Low testosterone is first confirmed with fasting morning total testosterone measured on two separate mornings. The safety baseline then usually includes hemoglobin and hematocrit, PSA for men over 40, a lipid panel and a blood pressure check. These steps reflect Endocrine Society and AUA guidance and FDA testosterone labeling.

How often are labs checked on TRT?

The Endocrine Society recommends checking testosterone and hematocrit at 3 to 6 months, at 12 months, then yearly. FDA labeling adds periodic hematocrit, blood pressure and PSA monitoring. A licensed clinician sets the actual schedule based on your results and history.

What is hematocrit and why does it matter on TRT?

Hematocrit is the share of blood volume made up of red blood cells, and testosterone can raise it. The AUA uses a baseline above 50% and a level of 54% or higher on therapy as decision points. FDA labeling lists polycythemia as a warning and calls for periodic monitoring.

Is PSA testing part of TRT monitoring?

Yes. PSA is measured before starting in men over 40 and monitored during treatment, with prostate cancer risk evaluated in the first year. Testosterone is contraindicated in men with known or suspected prostate cancer.

Do lab reference ranges differ?

Yes. Reference ranges vary between labs, so results are read against the range the reporting lab provides. The Endocrine Society recommends accurate assays and rigorously derived reference ranges for interpreting testosterone results. A licensed clinician interprets your numbers alongside your symptoms and history.

Is lab work part of New Blue hormone care?

Yes. Lab work is part of every New Blue hormone pathway, including the injectable testosterone protocol, alongside a live visit with a licensed clinician. The clinician decides whether therapy is appropriate and which follow-up labs are needed.

Sources

1. Evaluation and Management of Testosterone Deficiency: AUA Guideline. Journal of Urology, 2018. https://doi.org/10.1016/j.juro.2018.03.115
2. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology and Metabolism, 2018. https://pubmed.ncbi.nlm.nih.gov/29562364/
3. AZMIRO (testosterone cypionate) injection: prescribing information. U.S. National Library of Medicine, DailyMed (FDA-approved labeling), 2025. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=235b5625-570d-3fba-e063-6394a90aa2d1
4. Testosterone Cypionate Injection, USP: drug label. U.S. National Library of Medicine, DailyMed, n.d. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=6bb7d3cc-2b5a-4a48-858e-5421c68b6989
5. FDA issues class-wide labeling changes for testosterone products. U.S. Food and Drug Administration, 2025. https://www.fda.gov/drugs/drug-alerts-and-statements/fda-issues-class-wide-labeling-changes-testosterone-products
6. Cardiovascular Safety of Testosterone-Replacement Therapy. The New England Journal of Medicine, 2023. https://pubmed.ncbi.nlm.nih.gov/37326322/
7. Current National and International Guidelines for the Management of Male Hypogonadism: Helping Clinicians to Navigate Variation in Diagnostic Criteria and Treatment Recommendations. Endocrinology and Metabolism (Seoul, Korea), 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC7520594/
8. An Individualized Approach to Managing Testosterone Therapy in the Primary Care Setting. International Journal of General Medicine, 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9552794/

Medical disclaimer: This article is for educational purposes only and is not medical advice. Decisions about testing, diagnosis and treatment are made by a licensed clinician based on your individual history and results. New Blue Health is a technology and administrative services platform, not a medical provider.