What It Is

Total testosterone measures the entire amount of testosterone circulating in your blood, including both the protein-bound fraction (attached to SHBG and albumin) and the small free fraction. It is the primary marker used to diagnose hypogonadism (low T) and to monitor dosing adequacy on TRT. Produced mainly by the Leydig cells in the testes, testosterone drives muscle growth, bone density, red blood cell production, libido, mood, and cognitive function.

Why It's Tested on TRT

Total testosterone is the cornerstone lab for every TRT follow-up. It confirms your dosing protocol is bringing levels into the therapeutic range and helps your provider titrate the dose up or down. Drawing blood at trough (the day of or the day before your next injection) gives the most accurate picture of your lowest circulating level, ensuring you stay above the symptomatic threshold throughout your dosing cycle.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Below range (<264 ng/dL): Dose is insufficient, absorption issues, or poor injection technique. Symptoms of low T (fatigue, low libido, brain fog) likely persist.
• Low-normal (264–500 ng/dL): Many men still experience symptoms in this range. A dose increase or protocol change (e.g., more frequent injections) is often warranted.
• Optimal (600–900 ng/dL): Sweet spot for most men — symptom resolution with minimal side-effect risk.
• Supraphysiologic (>1,000 ng/dL): Increased risk of polycythemia, acne, hair loss, mood changes. Dose reduction recommended.

Interventions

What It Is

Prostate-specific antigen (PSA) is a protein produced exclusively by prostate cells. A small amount normally leaks into the bloodstream, and the PSA blood test measures that concentration. Elevated PSA can indicate benign prostatic hyperplasia (BPH), prostatitis (prostate inflammation/infection), or prostate cancer, though it is not cancer-specific on its own.

Why It's Tested on TRT

Testosterone therapy can cause a modest increase in PSA, typically 0.3–0.5 ng/mL in the first 6–12 months, because testosterone stimulates prostate cell growth. Monitoring PSA ensures any clinically significant rise is caught early. A rapid increase (>1.4 ng/mL over 12 months) or crossing the 4.0 ng/mL threshold warrants further evaluation, including possible urology referral. Baseline PSA should be drawn before starting TRT, with follow-up at 3, 6, and 12 months, then annually.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• < 2.0 ng/mL: Ideal. Low risk. Continue routine monitoring.
• 2.0 – 4.0 ng/mL: Gray zone. Evaluate trend over time. Consider free PSA ratio or PSA density if rising.
• > 4.0 ng/mL: Warrants urology referral, digital rectal exam, and possible prostate MRI or biopsy. TRT may need to be paused pending evaluation.
• Velocity > 0.75 ng/mL/year: Suspicious regardless of absolute value. Urology referral recommended.

Interventions

What It Is

The comprehensive metabolic panel is a group of 14 blood tests that provide a snapshot of your body's chemical balance and metabolism. It evaluates kidney function, liver function, electrolyte and fluid balance, and blood sugar levels. The CMP is one of the most commonly ordered lab panels and serves as a broad screening tool for overall health.

Why It's Tested on TRT

Testosterone is metabolized by the liver, so monitoring liver enzymes (ALT, AST, ALP) ensures hepatic safety, especially with oral testosterone formulations. Kidney markers (BUN, creatinine, eGFR) are important because TRT can increase muscle mass, which raises creatinine independently of kidney damage. Glucose monitoring detects insulin resistance changes, as TRT often improves insulin sensitivity and fasting glucose. Electrolytes and calcium are checked to ensure overall metabolic stability.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Elevated ALT/AST: May indicate liver stress. Oral testosterone (methyltestosterone) is most hepatotoxic — injectable cypionate/enanthate rarely cause significant liver enzyme elevation. Heavy training can also raise AST. If ALT > 3x upper limit, further hepatic workup is needed.
• Elevated creatinine / low eGFR: On TRT, increased muscle mass raises creatinine production, which can lower calculated eGFR without true kidney damage. Cystatin C can be ordered to differentiate. Dehydration also raises creatinine.
• Elevated fasting glucose: TRT often improves insulin sensitivity over time, but metabolic syndrome, poor diet, or weight gain can keep glucose elevated. Values 100–125 mg/dL indicate prediabetes.
• Electrolyte imbalances: TRT can cause mild fluid retention through sodium reabsorption. Low potassium may result from diuretic use. High calcium warrants parathyroid evaluation.
• Low albumin: May suggest chronic inflammation, liver dysfunction, or malnutrition — affects testosterone binding (albumin loosely binds ~50% of total T).

Interventions

Full write-up covered in the Entry Tier above. Total testosterone remains the primary dosing marker in every tier.

Full write-up covered in the Entry Tier above. PSA monitoring is essential at every level of TRT care.

Full write-up covered in the Entry Tier above. The CMP continues to monitor liver, kidney, electrolyte, and glucose status.

What It Is

Luteinizing hormone (LH) is a gonadotropin produced by the anterior pituitary gland. In men, LH signals the Leydig cells in the testes to produce testosterone. It is released in a pulsatile pattern, regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus. LH is a key player in the hypothalamic-pituitary-gonadal (HPG) axis, the hormonal feedback loop that controls testosterone production.

Why It's Tested on TRT

When you take exogenous testosterone, your brain detects the elevated testosterone level and suppresses GnRH release, which in turn suppresses LH to near-zero. This is expected and normal on TRT. A suppressed LH confirms your body is absorbing the exogenous testosterone. If LH is NOT suppressed on TRT, it may indicate non-compliance, poor absorption, or a pituitary adenoma producing LH autonomously. LH is also critical for pre-TRT diagnosis: elevated LH with low testosterone indicates primary hypogonadism (testicular failure), while low LH with low testosterone indicates secondary hypogonadism (pituitary/hypothalamic issue).

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Suppressed / undetectable (< 0.5 mIU/mL): Expected on exogenous testosterone. Confirms the HPG axis is responding to the external testosterone source. No action needed.
• Detectable / normal range while on TRT: Unexpected. Evaluate medication compliance, injection technique, and testosterone absorption. Consider checking testosterone levels to confirm therapy is reaching the bloodstream.
• Pre-TRT elevated (> 8.6 mIU/mL): Indicates primary hypogonadism — the pituitary is working hard but the testes cannot produce adequate testosterone. Often seen with testicular damage, Klinefelter syndrome, or age-related testicular decline.
• Pre-TRT low (< 1.7 mIU/mL) with low T: Indicates secondary hypogonadism. Pituitary MRI should be considered to rule out adenoma or other lesions.

Interventions

What It Is

Follicle-stimulating hormone (FSH) is the second gonadotropin produced by the anterior pituitary gland. In men, FSH acts on the Sertoli cells in the seminiferous tubules of the testes, driving spermatogenesis (sperm production). While LH controls testosterone production, FSH controls fertility — the two work in tandem within the HPG axis.

Why It's Tested on TRT

Like LH, FSH will be suppressed to near-zero on exogenous testosterone because the pituitary shuts down gonadotropin secretion when it detects adequate circulating testosterone. This suppression is why TRT causes reduced sperm production and potential infertility. Monitoring FSH is critical for men who want to preserve fertility while on TRT, as it quantifies how profoundly spermatogenesis is being suppressed. If fertility is desired, HCG or a SERM protocol may be added.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Suppressed / undetectable (< 0.7 mIU/mL): Expected on TRT. Spermatogenesis is likely impaired. If fertility is not a concern, this is normal and requires no intervention.
• Detectable while on TRT: Similar to LH, suggests compliance or absorption issues. Could also indicate concurrent HCG use is partially maintaining pituitary activity.
• Pre-TRT elevated (> 12.4 mIU/mL): Suggests primary testicular failure. The pituitary is producing excess FSH trying to stimulate sperm production from damaged or dysfunctional testes.
• Pre-TRT low with low T: Indicates secondary (central) hypogonadism. Consider pituitary workup.

Interventions

What It Is

The complete blood count is a panel of tests that evaluates the three major types of cells in your blood: red blood cells (oxygen carriers), white blood cells (immune defenders), and platelets (clotting agents). It provides information about overall health, oxygen-carrying capacity, infection risk, and clotting function. The CBC is one of the most important safety labs on TRT.

Why It's Tested on TRT

Testosterone powerfully stimulates erythropoiesis (red blood cell production) by increasing erythropoietin (EPO) from the kidneys and directly stimulating bone marrow. This is why TRT is the number one cause of secondary polycythemia (elevated red blood cells) in men. Elevated hematocrit increases blood viscosity, which raises the risk of blood clots, stroke, and cardiovascular events. Hemoglobin and hematocrit are the two most critical markers to monitor — if hematocrit exceeds 54%, intervention is required.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Elevated hematocrit (> 51%): TRT-induced erythrocytosis. If hematocrit exceeds 54%, the risk of thromboembolic events increases significantly. Therapeutic phlebotomy (blood donation) is first-line treatment. Dose reduction or increased injection frequency also helps.
• Elevated hemoglobin (> 17.7 g/dL): Parallels hematocrit elevation. Often the first marker to trigger intervention on TRT.
• Elevated RBC (> 5.80 x10&sup6;/μL): Consistent with polycythemia. More common with higher testosterone doses and in men living at high altitudes.
• Elevated RDW (> 15.4%): Suggests mixed red cell populations, which can occur when TRT rapidly stimulates new (larger) red blood cell production alongside older cells.
• Low WBC (< 3.4 x10³/μL): Not typically TRT-related. Warrants evaluation for infection, autoimmune conditions, or bone marrow issues.
• Low platelets (< 150 x10³/μL): Not common on TRT. If present, evaluate for liver disease, autoimmune conditions, or medication effects.

Interventions

Full write-ups for these six biomarkers are covered in the Entry Tier and Baseline Tier above. All remain part of the Optimized panel.

What It Is

Free testosterone is the small fraction of total testosterone (typically 2–3%) that circulates unbound to proteins in the blood. Unlike the majority of testosterone that is bound to sex hormone-binding globulin (SHBG) or albumin, free testosterone is immediately available to enter cells and activate androgen receptors. It is the biologically active form that directly drives muscle growth, libido, energy, mood, and cognitive function.

Why It's Tested on TRT

A man can have a normal total testosterone level but still experience symptoms of low T if his SHBG is elevated (from aging, liver conditions, thyroid disease, or certain medications), which traps testosterone in its bound form. Free testosterone reveals the true amount of bioavailable hormone reaching your tissues. On TRT, monitoring free T ensures the therapy is delivering adequate active hormone, not just raising total numbers. It is particularly important for men over 40, as SHBG rises approximately 1–2% per year with age.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Low free T (< 10 ng/dL) with normal total T: Elevated SHBG is binding most of the testosterone. Common with aging, hyperthyroidism, liver disease, or medications like anticonvulsants. Symptoms of low T persist despite "normal" labs.
• Low free T with low total T: Dose increase warranted. Both forms are insufficient.
• Optimal free T (15–25 ng/dL): Best correlation with symptom resolution and quality of life improvements on TRT.
• Very high free T (> 30 ng/dL): Risk of increased estrogen conversion (aromatization), acne, hair loss, irritability, and polycythemia. Dose reduction may be needed.

Interventions

What It Is

Thyroid-stimulating hormone is produced by the anterior pituitary gland and acts as the master regulator of thyroid function. TSH tells the thyroid gland to produce thyroid hormones (T4 and T3), which control metabolism, energy production, body temperature, heart rate, and protein synthesis. TSH operates on a negative feedback loop: when thyroid hormones are low, TSH rises; when thyroid hormones are adequate, TSH decreases.

Why It's Tested on TRT

Thyroid function and testosterone are deeply interconnected. Hypothyroidism increases SHBG, which binds more testosterone and reduces free T — potentially undermining TRT effectiveness. Conversely, hyperthyroidism also raises SHBG and accelerates testosterone clearance. Symptoms of hypothyroidism (fatigue, weight gain, brain fog, depression) overlap significantly with low testosterone, making it essential to rule out or co-manage thyroid dysfunction. Optimizing thyroid function amplifies the benefits of TRT.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Elevated TSH (> 4.5 mIU/L): Indicates hypothyroidism (underactive thyroid). The pituitary is working harder to stimulate an underperforming thyroid. Can cause fatigue, weight gain, constipation, cold intolerance, and elevated SHBG — all of which blunt TRT benefits.
• TSH 2.5–4.5 mIU/L: Subclinical hypothyroidism. Many functional medicine providers treat in this range if symptoms are present and Free T3/T4 are suboptimal.
• Low TSH (< 0.45 mIU/L): Suggests hyperthyroidism (overactive thyroid) or excessive thyroid medication. Can cause anxiety, rapid heart rate, weight loss, tremors, and elevated SHBG.
• TSH 1.0–2.5 mIU/L: Optimal range. Best metabolic function and synergy with TRT.

Interventions

What It Is

Free T4 measures the unbound, active form of thyroxine — the primary hormone produced by the thyroid gland. T4 serves as a reservoir hormone: the thyroid produces about 80% T4 and 20% T3, and T4 is converted to the more potent T3 in peripheral tissues (liver, kidneys, muscles). Free T4 is the most stable thyroid hormone to measure and is less susceptible to daily fluctuations than T3.

Why It's Tested on TRT

Free T4 helps differentiate between different thyroid disorders when TSH is abnormal. It also reveals the thyroid gland's actual output independent of pituitary regulation. In TRT patients, adequate Free T4 is essential for maintaining metabolic rate, energy levels, and efficient testosterone utilization. Low Free T4 impairs protein synthesis and can reduce the anabolic effects of testosterone on muscle tissue.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Low Free T4 (< 0.82 ng/dL): Confirms hypothyroidism (when TSH is elevated). The thyroid is underproducing. Expect fatigue, weight gain, and blunted TRT response.
• Low-normal Free T4 (0.82–1.1 ng/dL) with elevated TSH: Early or subclinical hypothyroidism. Consider treatment if symptoms are present.
• High Free T4 (> 1.77 ng/dL): Hyperthyroidism (if TSH is suppressed) or overmedication with levothyroxine. Can cause anxiety, palpitations, and excess SHBG.
• Normal Free T4 with low Free T3: Suggests a T4-to-T3 conversion problem (common with selenium or zinc deficiency, chronic stress, or inflammation).

Interventions

What It Is

Free T3 is the unbound, biologically active form of triiodothyronine — the most potent thyroid hormone. While T4 is a relatively inactive precursor, T3 is 3–5 times more metabolically active and is the form that actually enters cells and drives metabolic processes. About 80% of circulating T3 is produced by the conversion of T4 in peripheral tissues (primarily the liver and kidneys), while the remaining 20% is produced directly by the thyroid gland.

Why It's Tested on TRT

Free T3 is the true measure of active thyroid metabolism at the cellular level. Many patients have normal TSH and Free T4 but low Free T3 due to poor peripheral conversion — a condition that causes persistent fatigue, weight gain, and brain fog despite "normal" standard thyroid labs. For TRT patients, optimal Free T3 is critical because T3 directly influences androgen receptor sensitivity, muscle protein synthesis, fat metabolism, and energy production. Low T3 can make TRT feel less effective even at adequate testosterone doses.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Low Free T3 (< 2.5 pg/mL): May indicate poor T4-to-T3 conversion, low calorie intake (especially low-carb diets), chronic stress, inflammation, or selenium/zinc deficiency. Patients often feel fatigued despite normal TSH.
• Low-normal Free T3 (2.5–3.0 pg/mL): Suboptimal. Many patients report improved energy, cognition, and body composition when Free T3 is in the 3.0–4.0 pg/mL range.
• High Free T3 (> 4.4 pg/mL): May indicate hyperthyroidism, over-supplementation with T3, or thyroiditis. Can cause anxiety, insomnia, rapid heart rate, and tremors.
• Reverse T3 dominance: When the body converts T4 into reverse T3 (inactive) instead of active T3, often from chronic stress, illness, or caloric restriction. Check reverse T3 if Free T3 is low with normal Free T4.

Interventions

What It Is

The lipid panel measures the major fats and fat-like substances in your blood that are key indicators of cardiovascular health. It includes total cholesterol, LDL ("bad" cholesterol), HDL ("good" cholesterol), triglycerides, and calculated VLDL. Cholesterol is essential for hormone production — in fact, all steroid hormones, including testosterone, are synthesized from cholesterol — but imbalanced lipids increase the risk of atherosclerosis, heart attack, and stroke.

Why It's Tested on TRT

Testosterone therapy has a complex relationship with lipid metabolism. TRT generally improves the overall lipid profile by reducing total cholesterol and triglycerides, and may modestly improve insulin sensitivity. However, supraphysiologic doses can lower HDL cholesterol. Additionally, testosterone is synthesized from cholesterol, so monitoring ensures adequate substrate availability. Lipid panels are recommended at baseline, 6 months, and annually on TRT to track cardiovascular risk trends.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Elevated LDL (> 130 mg/dL): Increased cardiovascular risk. Not typically worsened by TRT at physiologic doses, but lifestyle, genetics (familial hypercholesterolemia), and diet are primary drivers. Consider advanced lipid testing (LDL particle number, Lp(a)).
• Low HDL (< 40 mg/dL): Supraphysiologic TRT doses or oral androgens can suppress HDL. This is one reason to keep testosterone within the therapeutic range. Low HDL impairs reverse cholesterol transport and increases cardiovascular risk.
• Elevated triglycerides (> 150 mg/dL): Strongly associated with insulin resistance, metabolic syndrome, and poor diet (excess carbohydrates and alcohol). TRT often helps lower triglycerides over time, but dietary intervention is the primary treatment.
• Very low total cholesterol (< 150 mg/dL): While rare, excessively low cholesterol can impair steroid hormone synthesis and has been associated with mood disorders. Adequate cholesterol is needed as a precursor for testosterone production.

Interventions

Full write-ups for these ten biomarkers are covered in the Entry, Baseline, and Optimized tiers above. All remain part of the Ultimate panel.

What It Is

Insulin-like growth factor 1 (IGF-1) is a peptide hormone produced primarily by the liver in response to growth hormone (GH) stimulation. It mediates many of the anabolic effects attributed to growth hormone, including muscle growth, bone density, tissue repair, collagen synthesis, and cellular regeneration. IGF-1 levels serve as a stable, reliable proxy for growth hormone status because GH itself is released in pulsatile bursts and is difficult to measure accurately with a single blood draw.

Why It's Tested on TRT

Testosterone and growth hormone have a synergistic relationship. TRT can modestly increase IGF-1 levels by stimulating GH release and enhancing hepatic IGF-1 production. Monitoring IGF-1 provides insight into the overall anabolic environment of the body — when both testosterone and IGF-1 are optimized, patients experience the greatest improvements in muscle mass, recovery, body composition, and anti-aging markers. Low IGF-1 despite adequate TRT may indicate GH deficiency, poor sleep, caloric restriction, or liver dysfunction. Excessively high IGF-1 warrants investigation for acromegaly or pituitary adenoma.

Reference Ranges (Males)

What Abnormal Results Mean on TRT

• Low IGF-1 (below age-adjusted range): May indicate growth hormone deficiency (GHD), inadequate sleep (most GH is released during deep sleep), caloric restriction, liver disease, or chronic illness. Symptoms include difficulty building muscle, poor recovery, thin skin, increased body fat (especially abdominal), and accelerated aging.
• Low-normal IGF-1: Suboptimal anabolic environment. Optimizing sleep, nutrition, and exercise can often raise levels. Consider GH stimulation testing if clinically indicated.
• Optimal IGF-1 (upper third of age-adjusted range): Associated with best body composition, recovery, cognitive function, and longevity markers. The "sweet spot" for anti-aging and performance.
• Very high IGF-1 (> 300 ng/mL): If not on GH therapy, warrants evaluation for pituitary adenoma (acromegaly). Chronically elevated IGF-1 is associated with increased cancer risk in some studies.

Interventions