Low Testosterone: Symptoms, Lab Ranges, and When to Treat

Testosterone influences dozens of systems in the male body. When levels fall below your optimal range — which varies between individuals — you may experience:

Physical symptoms:

• Persistent fatigue and low energy, even after adequate sleep

• Decreased muscle mass and difficulty building or maintaining muscle

• Increased body fat, especially around the abdomen

• Reduced bone density (which increases fracture risk over time)

• Erectile dysfunction or reduced morning erections

• Decreased body and facial hair

Cognitive and emotional symptoms:

• Brain fog, poor concentration, or memory problems

• Low motivation or a general sense of flatness

• Irritability, anxiety, or depression

• Reduced competitive drive

Sexual symptoms:

• Low or absent libido

• Difficulty achieving or maintaining erections

• Reduced ejaculatory volume

Many men experience several of these simultaneously but assume it's 'just aging.' In many cases, it's a treatable hormonal deficiency.

A standard testosterone lab report lists 'total testosterone' with a reference range of roughly 300–1,000 ng/dL. But this range is misleading for two reasons:

First, it's based on all men aged 20–80 in the reference population — a 75-year-old's 'normal' is not the same as a 40-year-old's optimal.

Second, total testosterone only tells part of the story. Free testosterone (the biologically active fraction) matters more for symptoms. Sex Hormone Binding Globulin (SHBG) determines how much of your total testosterone is available to tissues. A man with a total T of 600 ng/dL but high SHBG may have functionally low testosterone.

A complete evaluation should include: Total Testosterone (morning draw), Free Testosterone, SHBG, LH and FSH (to distinguish primary vs. secondary hypogonadism), Estradiol, CBC, and a metabolic panel.

At Peak Medical Wellness, we review your full picture — not just whether you fall within a reference range, but whether your levels support your age, symptoms, and health goals.

There's no universal threshold at which every man 'should' start testosterone replacement therapy (TRT). Treatment decisions are based on the combination of symptoms and labs.

Generally, TRT is appropriate when a man has both symptomatic low T (multiple symptoms significantly affecting quality of life) and confirmed low levels on appropriately timed lab work.

Men with total testosterone consistently below 300 ng/dL are typically considered for treatment regardless of symptoms. Men in the 300–500 ng/dL range who are symptomatic are also candidates. The key is that labs and symptoms align.

TRT is typically not recommended for men planning to father children in the near term, as it suppresses sperm production. Alternative therapies like Clomiphene (clomid) or HCG can raise testosterone while preserving fertility.

Testosterone can be delivered several ways, each with trade-offs:

Injections (Testosterone Cypionate or Enanthate) — Weekly or biweekly subcutaneous or intramuscular injections. Cost-effective, flexible dosing. Testosterone levels fluctuate between injections.

Pellets — Small pellets implanted under the skin every 3–6 months. Provides stable, steady-state testosterone levels. Minor in-office procedure.

Topical gels or creams — Applied daily. Convenient but carry a risk of transfer to partners or children.

Once TRT begins, follow-up labs at 6–8 weeks assess response and allow for dose optimization. Ongoing monitoring includes hematocrit (TRT can increase red blood cell production) and estradiol (testosterone aromatizes to estrogen).

Most men notice improvements in energy and mood within 3–6 weeks, with fuller effects on body composition and libido at 3–6 months.