Testosterone Replacement Therapy: The Complete Beginner's Guide

Written by Adam Maggio | Medically reviewed by Dr. Mitchell Ross, MD, ABAARM

TRT is a medical treatment for hypogonadism (low testosterone) that involves replacing testosterone to physiological levels. It requires a diagnosis, baseline bloodwork, and ongoing monitoring. Benefits include improved energy, libido, body composition, mood, and cognitive function. Risks are manageable with proper monitoring.

What is TRT?

Testosterone Replacement Therapy (TRT) is a medical treatment that replaces testosterone in men whose bodies do not produce adequate amounts. It is prescribed for hypogonadism — a condition characterized by low testosterone levels (typically below 300 ng/dL) combined with symptoms such as fatigue, low libido, erectile dysfunction, depression, reduced muscle mass, and increased body fat.

Do You Need TRT?

TRT is appropriate when: total testosterone is consistently below 300 ng/dL on two separate morning measurements; symptoms of hypogonadism are present; secondary causes of low testosterone (obesity, sleep apnea, medications, pituitary tumors) have been ruled out or addressed. TRT is not appropriate as a performance-enhancing drug in men with normal testosterone levels, though this distinction is increasingly blurred in clinical practice.

Getting Started: The Diagnostic Process

Step 1: Symptoms assessment — document your symptoms and their impact on quality of life. Step 2: Baseline bloodwork — total testosterone, free testosterone, LH, FSH, estradiol, SHBG, complete blood count, comprehensive metabolic panel, PSA (for men over 40). Step 3: Find a knowledgeable provider — endocrinologist, urologist, or men's health specialist. Step 4: Discuss treatment options — injectable testosterone is typically the most cost-effective and controllable option.

TRT Formulations

Injectable testosterone (cypionate or enanthate): most common, cost-effective, highly controllable. Typical starting dose: 100–150 mg weekly or 50–75 mg twice weekly. Transdermal gels/creams: convenient, no injections, but variable absorption and transfer risk. Testosterone pellets: inserted subcutaneously every 3–6 months, convenient but not adjustable. Nasal gel (Natesto): three times daily application, preserves fertility better than other forms.

Monitoring on TRT

Bloodwork every 3 months for the first year, then every 6 months once stable. Key parameters: total testosterone (target: 600–900 ng/dL), free testosterone (upper quartile), estradiol (target: 20–40 pg/mL), hematocrit (must remain below 54%), PSA (annual for men over 40). Adjust dose based on bloodwork and symptoms, not numbers alone.

What to Expect

Weeks 1–4: improved energy and mood (often the first changes noticed). Weeks 4–8: improved libido and sexual function. Months 2–4: improved body composition (reduced fat, increased muscle). Months 4–12: continued body composition improvements, bone density improvements. Full benefits may take 12–24 months to manifest completely.