Hormones Checked Before Starting TRT: Pre-TRT Lab Guide

Men considering testosterone replacement therapy (TRT) need specific blood tests before the first dose. The American Urological Association (AUA) and the Endocrine Society both require two early-morning testosterone measurements on separate days, combined with pituitary hormones (LH, FSH), safety labs (hematocrit, PSA), and in some cases prolactin and estradiol (Bhasin et al., 2018; Mulhall et al., 2018). Skipping any part of that workup may lead to an incomplete picture, unnecessary treatment, or avoidable side effects.

Testosterone replacement is a treatment for men with diagnosed hypogonadism, a condition defined by consistently low serum testosterone combined with clinical symptoms such as reduced libido, fatigue, or loss of lean body mass. The hormones checked before starting TRT determine whether testosterone is the right treatment and, if so, where the problem originates. Ordering these labs before the first prescription protects both health and time.

A 2026 University of Michigan chart review of 200 men with a hypogonadism diagnosis found that only 12% received a workup consistent with Endocrine Society and AUA guidelines before their first testosterone prescription (Sinha and Papaleontiou, ENDO 2026, conference presentation). That number means the majority of men started treatment without adequate confirmation of the diagnosis or classification of its cause.

Why are two morning testosterone tests required?

A single low testosterone result is not a confirmed diagnosis. About 30% of men with a first value in the hypogonadal range have a normal concentration on repeat measurement (Bhasin et al., 2018). Both AUA and the Endocrine Society require two early-morning draws, each taken fasting, 1-3 weeks apart, ideally from the same laboratory and assay method.

The AUA uses total testosterone below 300 ng/dL as a reasonable cut-off supporting diagnosis (Moderate Recommendation; Grade B) (Mulhall et al., 2018). That threshold is not universal. The Travison 2017 harmonized reference study placed the 2.5th percentile at 264 ng/dL and the 5th percentile at 303 ng/dL in healthy nonobese men ages 19-39, with a full range of 264-916 ng/dL (Travison et al., 2017). A man with a result between 264 and 303 ng/dL may read as "low" or "normal" depending on the laboratory's method. The Endocrine Society recommends using CDC Hormone Standardization (HoSt)-certified assays for this reason (CDC, 2026).

Morning timing matters because testosterone follows a circadian pattern, peaking between 8-10 AM and declining through the afternoon. An afternoon or non-fasting draw can produce an artificially low result that doesn't reflect the morning peak.

What does luteinizing hormone (LH) tell a provider?

LH is the pituitary signal that directs the Leydig cells in the testes to produce testosterone. Once two low testosterone results are confirmed, LH is the test that separates primary hypogonadism from secondary hypogonadism.

High LH combined with low testosterone points to testicular failure (primary or hypergonadotropic hypogonadism). The testes aren't responding even though the pituitary is sending a strong signal. Treatment in this case typically involves testosterone replacement, depending on symptoms, goals, and fertility considerations.

Low or inappropriately normal LH paired with low testosterone points to a pituitary or hypothalamic problem (secondary or hypogonadotropic hypogonadism). This distinction matters because secondary causes can include reversible conditions, and treatment options differ. AUA gives LH and FSH testing in all men with low testosterone a Strong Recommendation, Grade A (Mulhall et al., 2018).

How does FSH add to the picture?

Follicle-stimulating hormone (FSH) is produced alongside LH by the anterior pituitary, but its main target is the Sertoli cells that support sperm production. Elevated FSH in a man with low testosterone indicates damaged seminiferous tubules and impaired spermatogenesis, a finding with direct fertility implications.

The Endocrine Society recommends measuring FSH with LH to classify hypogonadism (Bhasin et al., 2018). AUA adds that a reproductive evaluation is warranted when fertility is a concern (Moderate; Grade B). Exogenous testosterone suppresses both LH and FSH, which suppresses sperm production. AUA advises against prescribing testosterone to men currently trying to conceive (Strong; Grade A).

That suppression is expected on treatment, and recovery after stopping is variable. It is not guaranteed on a fixed timetable.

When is prolactin required before TRT?

AUA recommends prolactin testing when low testosterone is paired with low or low-normal LH, because elevated prolactin (hyperprolactinemia) can suppress GnRH at the hypothalamic level and drive testosterone down through a different mechanism than testicular failure (Strong; Grade A) (Mulhall et al., 2018).

If prolactin stays persistently high without an obvious cause, AUA recommends an endocrine evaluation (Strong; Grade A). That workup may include pituitary imaging to rule out a prolactinoma, a benign tumor of the pituitary gland that produces prolactin. Starting testosterone without checking prolactin in a man with secondary hypogonadism can delay diagnosis of a sellar lesion.

Does free testosterone need its own test?

Total testosterone measures all testosterone in the blood, but a large portion is bound to sex hormone-binding globulin (SHBG) and albumin. Only unbound (free) testosterone is available to tissues. The Endocrine Society recommends measuring free testosterone when total testosterone falls near the lower limit of normal or when a condition that alters SHBG is present (Bhasin et al., 2018).

Conditions that lower SHBG, including obesity and insulin resistance, can make total testosterone appear low while free testosterone remains adequate. Conditions that raise SHBG, such as aging, hyperthyroidism, and some liver diseases, can make total testosterone look normal while free testosterone is genuinely low.

Method matters here. The Endocrine Society specifies equilibrium dialysis or a validated calculation (using SHBG and albumin) for free testosterone measurement. Analog "direct" free testosterone immunoassays lack specificity and are not recommended by the Endocrine Society. SHBG itself is not a hormone that is "treated," but without it, free testosterone cannot be accurately assessed.

Marek Diagnostics offers both individual biomarker testing and a Pre-TRT Panel that includes total testosterone by LC/MS and free testosterone by equilibrium dialysis, the methods clinical guidelines recommend.

Should estradiol be on every pre-TRT panel?

Testosterone converts to estradiol through a process called aromatization. AUA recommends estradiol before starting therapy only in men with breast symptoms or gynecomastia (Expert Opinion) (Mulhall et al., 2018). It is not a universal pre-treatment requirement in the AUA or Endocrine Society 2018 guidelines.

Many men's-health practices order a baseline sensitive estradiol (LC/MS-MS) for every client, even without breast symptoms. That is a clinical practice decision, not a guideline mandate. Checking a baseline has practical value: if gynecomastia develops on treatment, a before-and-after comparison exists. Marek Diagnostics offers a sensitive estradiol test by LC/MS-MS for this purpose.

What is the hematocrit threshold before starting TRT?

Testosterone can increase red blood cell production. If hematocrit (the percentage of blood volume occupied by red blood cells) rises too high, blood viscosity increases, and so does the risk of erythrocytosis-related complications.

AUA recommends measuring hemoglobin and hematocrit before offering testosterone therapy and informing the client about polycythemia risk (Strong; Grade A). If baseline hematocrit exceeds 50%, AUA advises considering withholding therapy until the cause is investigated (Mulhall et al., 2018). On treatment, the follow-up target is to keep hematocrit below 54%.

This is the safety lab people skip most often. Starting injectable testosterone with an already elevated hematocrit can produce erythrocytosis within the first months of therapy, leading to dose holds, therapeutic phlebotomy, or a thrombosis-risk conversation that could have been avoided with a single pre-treatment blood count.

Why is PSA checked before TRT?

Prostate-specific antigen (PSA) establishes a prostate-health baseline before starting a therapy that can raise PSA levels. AUA recommends PSA testing before commencement in men over 40 (Clinical Principle) (Mulhall et al., 2018).

Current FDA labeling generally contraindicates testosterone in men with known or suspected prostate cancer. In June 2026, HHS and FDA requested narrowing that contraindication to metastatic disease only (HHS, 2026). That request has not been finalized across all product labels. A baseline PSA does not diagnose prostate cancer by itself, but it provides a reference point for monitoring on treatment.

Guideline-required labs vs. commonly added labs

Not every marker drawn before TRT carries the same evidence grade. The table below separates what AUA and the Endocrine Society require from what many practices add for clinical context.

What changed in TRT labeling and safety data?

In February 2025, the FDA issued class-wide labeling changes for all testosterone products. The update added TRAVERSE trial results to all labels, removed the previous cardiovascular boxed warning language, retained the Limitation of Use for age-related hypogonadism, and added new blood-pressure warnings based on completed ambulatory blood-pressure monitoring (ABPM) studies (FDA, 2025).

The TRAVERSE trial enrolled 5,246 men with hypogonadism and preexisting cardiovascular disease or high cardiovascular risk. Its primary finding was that transdermal testosterone gel did not increase the rate of major adverse cardiac events (MACE) compared with placebo (7.0% vs. 7.3%; HR 0.96; 95% CI 0.78-1.17) (Lincoff et al., 2023). TRAVERSE also showed higher rates of atrial fibrillation (3.5% vs. 2.4%), pulmonary embolism (0.9% vs. 0.5%), and nonfatal arrhythmias (5.2% vs. 3.3%) in the testosterone group. The Endocrine Society July 2026 statement noted a roughly 50% relative increase in pulmonary embolism and an increased incidence of bone fractures among testosterone-treated men in TRAVERSE, and stated that long-term safety including prostate cancer remains unestablished.

These secondary signals are why pre-treatment hematocrit, cardiovascular risk assessment, and ongoing monitoring are recommended as part of responsible prescribing.

Getting pre-TRT labs right matters more than most men realize

The hormones checked before starting TRT are not a formality. They confirm the diagnosis, classify its cause, screen for reversible conditions, and set the safety baselines that guide every dose adjustment and follow-up visit. The ENDO 2026 chart review from the University of Michigan found that men with two or more comorbidities were less likely to receive a guideline-concordant workup (OR 0.25; 95% CI 0.08-0.8) (Sinha and Papaleontiou, ENDO 2026, conference presentation), meaning the men who need the most thorough evaluation before TRT are the ones least likely to get it.

A man considering testosterone replacement can ask his provider to show the pre-treatment lab list and compare it to what AUA and the Endocrine Society recommend. Marek Diagnostics offers a complete pre-TRT panel built to match these guidelines, with results reviewed alongside a licensed provider who can place each marker in clinical context.

Disclaimer: This blog post is intended for informational purposes only and should not be considered medical advice. Always consult a healthcare professional before making changes to your health routine.

FAQs

Do I need two testosterone tests, or is one morning lab enough? 

Guidelines require two early-morning measurements on separate days because a single low value often does not hold up on repeat. About 30% of men with a first result in the hypogonadal range have a normal concentration when retested (Bhasin et al., J Clin Endocrinol Metab. 2018;103(5):1715-1744). Starting treatment after one afternoon or non-fasting draw can mean months on a prescription that was never warranted.

Why check LH and FSH if testosterone is already confirmed low? 

LH and FSH classify the cause. High LH with low testosterone points to testicular failure (primary hypogonadism), while low or normal LH with low testosterone points to a pituitary or hypothalamic problem (secondary hypogonadism). AUA gives LH a Strong Recommendation, Grade A, for all men with confirmed low testosterone (Mulhall et al., J Urol. 2018;200(2):423-432). Skipping this step can delay the diagnosis of a reversible condition.

When is prolactin checked before starting TRT? 

AUA recommends prolactin when low testosterone is paired with low or low-normal LH (Strong; Grade A). Elevated prolactin from hyperprolactinemia or a pituitary mass can suppress the hormonal axis and requires different treatment than standard testosterone replacement.

Is free testosterone required, and which method counts? 

The Endocrine Society recommends free testosterone when total testosterone is near the lower limit of normal or when SHBG is likely altered by obesity, thyroid disease, or aging. The approved methods are equilibrium dialysis or a validated calculation using SHBG. Analog "direct" free testosterone immunoassays lack specificity and are not recommended by the Endocrine Society (Bhasin et al., J Clin Endocrinol Metab. 2018;103(5):1715-1744).

What hematocrit level should pause a first prescription? 

AUA recommends measuring hematocrit before starting TRT. If baseline hematocrit exceeds 50%, the guideline advises considering withholding therapy until the cause is investigated (Strong; Grade A). On treatment, the follow-up target is to keep hematocrit below 54% (Mulhall et al., J Urol. 2018;200(2):423-432).

Does every man need estradiol checked before TRT? 

AUA recommends estradiol before therapy only in men with breast symptoms or gynecomastia (Expert Opinion). It is not a required pre-TRT lab for all men in either AUA or Endocrine Society guidelines, though many practices order a baseline for comparison if symptoms develop on treatment.

How often do prescribed men actually receive this full workup? 

In a 200-man University of Michigan chart review presented at ENDO 2026, only 12% had two low morning testosterone results, LH and/or FSH, and no contraindications documented before the first prescription (Sinha and Papaleontiou, ENDO 2026). Asking a provider to show the pre-treatment lab list is a reasonable step before agreeing to start TRT.

References

• J Clin Endocrinol Metab. 2018;103(5):1715-1744

• J Urol. 2018;200(2):423-432

• J Clin Endocrinol Metab. 2017;102(4):1161-1173

• N Engl J Med. 2023;389(2):107-117

• FDA Class-Wide Labeling Changes. February 28, 2025

• HHS Requested Label Updates. June 18, 2026

• CDC Hormone Standardization Program (HoSt). Accessed 2025

• Endocrine Society Statement on TRT. July 16, 2026