Testosterone Blood Test: Normal Ranges and What Low T Means

Total vs Free Testosterone: Which Matters More

Testosterone circulates in two forms. Total testosterone measures all testosterone in blood — both the 60% bound tightly to sex hormone-binding globulin (SHBG), the 38% loosely bound to albumin, and the 2–3% that is free. Only free testosterone is biologically active and can enter cells. A person with normal total testosterone but very high SHBG may have inadequate free testosterone — and all the symptoms of low T.

Reference Ranges

Group	Total Testosterone	Free Testosterone
Men (lab normal)	264–916 ng/dL	9–30 pg/mL
Men (research-backed optimal)	500–900 ng/dL	15–25 pg/mL
Men (borderline low)	264–400 ng/dL	Below 9 pg/mL
Men (clinically low)	Below 264 ng/dL	Below 5 pg/mL
Women (premenopausal)	15–70 ng/dL	0.3–1.9 pg/mL

Always test testosterone in the morning (before 10 AM) — levels fall 20–40% by afternoon. The diagnosis of hypogonadism requires both low morning testosterone on at least two separate tests AND symptoms consistent with deficiency.

Causes of Low Testosterone in Men

Primary hypogonadism (testicular failure) produces low testosterone with elevated LH and FSH — the pituitary signals strongly but the testes cannot respond. Causes include Klinefelter syndrome, testicular injury, chemotherapy, and mumps orchitis.

Secondary hypogonadism (pituitary or hypothalamic failure) produces low testosterone with low or inappropriately normal LH and FSH. Common causes include obesity (aromatase in fat converts testosterone to estradiol), untreated obstructive sleep apnoea, chronic high stress and elevated cortisol, opioid use, anabolic steroid misuse, and pituitary adenoma.

Age-related decline is real but gradual — approximately 1% per year after age 30. Lifestyle factors dramatically accelerate this: visceral obesity, poor sleep, sedentary behaviour, heavy alcohol, and chronic illness all substantially lower testosterone.

Symptoms of Low Testosterone

Reduced libido and sexual function, decreased morning erections, low energy and motivation, difficulty building or maintaining muscle despite exercise, increased abdominal fat, low mood and irritability, reduced bone density, poor concentration, and low-grade anaemia are the characteristic symptoms. These overlap with many other conditions — which is why two confirmed low readings plus symptoms are needed for diagnosis.

What to Test Alongside Testosterone

A complete assessment includes: total and free testosterone, LH, FSH (to distinguish primary from secondary hypogonadism), SHBG, prolactin (elevated prolactin from a pituitary tumour suppresses testosterone), and a full metabolic panel. Estradiol is useful in men with gynecomastia or when aromatase excess is suspected.

Testosterone in Women

Testosterone in women is produced by the ovaries and adrenal glands. Low testosterone in women can contribute to reduced libido, fatigue, and difficulty maintaining muscle. Elevated testosterone — particularly alongside an elevated LH:FSH ratio, irregular cycles, and clinical signs — is a key diagnostic criterion for PCOS. Women's testosterone should always be interpreted alongside DHEAS, androstenedione, and SHBG.