Men with low total testosterone (TT) below 300 ng/dL face increased risks for all-cause mortality, cardiovascular disease, and metabolic syndrome (Wu et al., 2010, Journal of Clinical Endocrinology & Metabolism). Understanding your blood work is not just about confirming a diagnosis; it is about actively managing your health and optimizing your treatment. As an endocrinologist, I empower individuals to interpret their own data, fostering true health autonomy. The traditional diagnostic threshold for hypogonadism, often cited as total testosterone below 300 ng/dL, was established using a population that included older, sicker men in the 1970s. This benchmark may not reflect optimal health for all individuals, particularly younger, active men. Optimal TRT aims for a physiological range, not just a “normal” one.

Last Updated: October 2023

Core Hormone Markers on TRT

Monitoring your hormone panel provides crucial insights into the effectiveness and safety of your Testosterone Replacement Therapy (TRT). These markers guide dosage adjustments and identify potential side effects.

Total Testosterone (TT)

Total testosterone measures the total amount of testosterone in your blood, including both free (active) and bound testosterone. This is your primary metric for assessing TRT efficacy.

Pre-TRT Baseline: A level consistently below 300–350 ng/dL, especially with symptoms, indicates hypogonadism. Two separate morning measurements are typically required.
On TRT: The goal is to achieve levels in the upper physiological range, typically 800–1200 ng/dL, measured at trough (just before your next injection). If your levels are consistently below 700 ng/dL at trough, your dose may be too low or your injection frequency may need adjustment. Levels consistently above 1500 ng/dL may indicate an excessive dose.
Dosage Context: A common starting dose for testosterone cypionate or enanthate is 100–200mg per week. This can be split into more frequent injections (e.g., 50–100mg twice weekly) to maintain stable levels and reduce estrogenic side effects.

Free Testosterone (FT)

Free testosterone is the biologically active form of testosterone, unbound to proteins and available to target tissues. It is a critical indicator of how much testosterone your body can actually utilize.

Optimal Range on TRT: Aim for a free testosterone level between 15–25 pg/mL.
Calculation: Free testosterone is often calculated from total testosterone, Sex Hormone Binding Globulin (SHBG), and albumin. Direct measurement (equilibrium dialysis) is the gold standard but less common due to cost and availability.
Significance: Even with optimal total testosterone, low free testosterone suggests that most of your testosterone is bound, limiting its effect. This often points to high SHBG.

Sex Hormone Binding Globulin (SHBG)

SHBG is a protein produced primarily by the liver that binds to sex hormones, including testosterone, estrogen, and dihydrotestosterone (DHT). It regulates the amount of free hormone available to tissues.

Optimal Range: A healthy range is typically 15–50 nmol/L.
High SHBG: Can result in low free testosterone even with normal total testosterone. Factors like hyperthyroidism, high estrogen, or certain medications can elevate SHBG. TRT can sometimes slightly lower SHBG, but significant reductions often require addressing underlying causes.
Low SHBG: Can lead to higher free testosterone, potentially increasing symptoms of high estrogen or DHT at lower total testosterone levels. Insulin resistance, hypothyroidism, or anabolic steroid use can lower SHBG.

Estradiol (E2)

Estradiol is the primary estrogen in men, produced from testosterone via the aromatase enzyme. It plays a role in bone density, libido, and mood, but excessive levels can cause adverse effects.

Optimal Range on TRT: A common target for E2 on TRT is 20–40 pg/mL. Some men feel optimal slightly outside this range; symptom management is key.
Symptoms of High E2: Bloating, mood swings, anxiety, reduced libido, erectile dysfunction, gynecomastia. This often occurs with higher total testosterone doses or less frequent injections.
Symptoms of Low E2: Joint pain, dry skin, fatigue, low libido, anxiety, poor mood. Do not crash your E2.
Management: If E2 is elevated and symptomatic, options include:
- Increased injection frequency: Splitting your weekly testosterone dose into 2–3 smaller injections (e.g., 50mg testosterone cypionate 2x/week) can reduce peak testosterone levels and subsequent aromatization.
- Anastrozole: An aromatase inhibitor (AI) like anastrozole may be used sparingly to manage persistently high, symptomatic E2. A typical starting dose might be 0.25–0.5mg twice per week. Routine use of AIs is not recommended by major guidelines unless clinically indicated. “Routine concomitant use of an aromatase inhibitor with testosterone therapy is not recommended because of potential adverse effects on bone and lipid metabolism,” states the Endocrine Society Clinical Practice Guideline (Bhasin et al., 2018).

Luteinizing Hormone (LH) & Follicle-Stimulating Hormone (FSH)

These pituitary hormones stimulate testosterone production in the testes and sperm production.

Pre-TRT Baseline: Helps differentiate primary (testicular failure, high LH/FSH) from secondary hypogonadism (pituitary issue, low LH/FSH).
On TRT (without HCG): LH and FSH levels will typically be suppressed to <1.0 IU/L, indicating the pituitary has ceased stimulating natural testosterone production. This leads to testicular atrophy and infertility.
On TRT (with HCG): Human Chorionic Gonadotropin (HCG) mimics LH, stimulating Leydig cells in the testes to produce testosterone and maintain testicular size and function. If using HCG (e.g., 500–1000 IU per week), LH levels will remain suppressed, but the testes will be stimulated.
On Enclomiphene: Enclomiphene citrate blocks estrogen receptors in the pituitary, preventing negative feedback. This causes a rise in LH and FSH, stimulating endogenous testosterone production. LH/FSH levels will be elevated on enclomiphene (e.g., LH 5–10 IU/L, FSH 3–8 IU/L), with a goal of restoring endogenous testosterone. A common dose is 25mg daily.

Prolactin

Prolactin is a hormone primarily associated with lactation but can affect men’s health.

Optimal Range: Typically below 15–20 ng/mL.
High Prolactin: Can suppress GnRH release, leading to low testosterone and symptoms like reduced libido and erectile dysfunction. Causes include pituitary adenomas, certain medications, or chronic stress. Investigation is warranted if consistently elevated.

General Health Markers on TRT

While not direct hormone levels, these markers are crucial for monitoring overall health and TRT safety.

Complete Blood Count (CBC) – Hematocrit and Hemoglobin

TRT can increase red blood cell production, which needs careful monitoring.

Hematocrit (HCT): The percentage of red blood cells in your blood.
Hemoglobin (HGB): The protein in red blood cells that carries oxygen.
Optimal Range: Hematocrit should remain below 50%. Hemoglobin typically below 17.5 g/dL.
Risk of Polycythemia: Excessively high HCT/HGB (polycythemia) increases blood viscosity, raising the risk of blood clots, stroke, and heart attack.
Management: If HCT consistently rises above 50%, strategies include:
- Reducing TRT dose.
- Increasing injection frequency: This often smooths out peaks and troughs, reducing erythropoiesis.
- Therapeutic phlebotomy (blood donation): A common intervention to lower HCT.
- Adequate hydration.

Lipid Panel (Cholesterol)

TRT’s impact on cholesterol can vary.

Markers: Total Cholesterol, LDL (bad), HDL (good), Triglycerides.
Monitoring: While injectables generally have less negative impact on lipids than oral testosterone, regular monitoring is prudent. Some men may experience a slight decrease

Interpreting Your TRT Blood Work: A Comprehensive Guide