Testosterone Replacement Therapy (TRT) is a medical treatment designed to address the symptoms associated with low testosterone, a condition known as hypogonadism. The fundamental goal of TRT is not to maximize hormone levels but to restore a patient’s testosterone concentration to a normal, physiological range. This restoration aims to alleviate symptoms such as reduced libido, fatigue, or decreased muscle mass. Determining the correct dose is a complex, highly individualized process that requires rigorous medical supervision. The required dosage depends entirely on the patient’s biological response and chosen delivery method.
Initial Assessment for Dosage Calculation
Determining a starting dose involves comprehensive baseline blood testing and an assessment of symptoms. Physicians typically measure Total Testosterone (TT) and Free Testosterone (FT) to confirm hypogonadism. Since testosterone levels fluctuate, blood samples must be drawn in the early morning, usually between 8:00 AM and 10:00 AM, when the concentration is naturally at its peak.
A Total Testosterone level below 300 nanograms per deciliter (ng/dL) is considered low in a symptomatic patient. Levels between 300 ng/dL and 400 ng/dL are equivocal and often require a second measurement. In these borderline cases, Free Testosterone measurement becomes important.
Free Testosterone is the biologically active fraction not bound to proteins, providing a clearer picture of the hormone available to the body’s tissues. Patients with borderline TT but high Sex Hormone-Binding Globulin (SHBG) may have low FT, indicating a need for treatment. The decision to start therapy is guided by specific hypogonadal symptoms, such as reduced sexual thoughts or fewer morning erections, rather than relying on non-specific complaints like fatigue alone.
TRT Delivery Methods and Administration Schedules
The amount of testosterone prescribed is linked to the chosen delivery method, as each formulation has a different absorption profile and half-life.
Injectable Testosterone
Injectable testosterone, typically Cypionate or Enanthate, is an oil-based solution administered intramuscularly or subcutaneously. A common starting dose falls between 75 and 100 milligrams per week, though the range can be up to 250 mg per week.
Less frequent dosing, such as bi-weekly injections, can cause undesirable peaks in hormone concentration followed by a significant drop, or “trough,” before the next dose. This fluctuation can cause mood swings and energy dips. Therefore, many protocols favor a smaller dose administered more frequently, such as twice weekly, to maintain a more stable, physiological concentration.
Topical Applications
Topical gels and creams are applied daily, usually to the shoulders, upper arms, or abdomen. Starting doses are often around 50 milligrams per day. Only a fraction of this applied amount is absorbed due to skin barrier properties, and absorption varies significantly between patients. Patches, applied daily, typically deliver about 4 milligrams of testosterone over 24 hours.
Implants
Long-acting subcutaneous pellets, delivering 150 to 450 milligrams of testosterone, are implanted under the skin every three to six months. This method provides a steady hormone release, minimizing the daily self-dosing requirement. However, pellets offer less flexibility for immediate dosage adjustments once implanted.
Monitoring, Adjusting, and Maintaining Therapeutic Levels
Determining the final, optimal dose is a dynamic process. Follow-up blood work is typically scheduled within four to six weeks of starting treatment or changing a dose to assess the body’s initial response and catch any early side effects.
Providers monitor several other markers beyond Total and Free Testosterone to ensure safety and efficacy:
- Hematocrit and Hemoglobin levels, as testosterone stimulates red blood cell production, and an excessive rise can increase blood viscosity.
- Estradiol, a form of estrogen that testosterone converts into, as high levels can lead to side effects like breast tenderness.
- Prostate-Specific Antigen (PSA) levels, monitored in men over 40 to screen for potential prostate changes.
Dose adjustments are based on laboratory results and the patient’s reported symptoms. If levels remain low or symptoms persist, the dose is increased in small increments. Conversely, if levels are too high, or if the patient experiences side effects like acne or irritability, the dose is decreased or the administration frequency is adjusted. The objective is to maintain hormone levels in the middle-to-upper portion of the normal adult male range while resolving hypogonadism symptoms.