Yes, tamoxifen can increase testosterone levels in men, but it is by no means a safe or approved over‑the‑counter "testosterone booster."
Tamoxifen is a prescription drug indicated primarily for breast cancer. When used in men, it is off‑label – prescribed only in specific medical situations (e.g., male infertility, certain types of male breast cancer, or prevention/treatment of gynecomastia caused by anabolic steroid use) and strictly under a doctor's supervision.
How it works and clinical evidence
Tamoxifen is a selective estrogen receptor modulator (SERM). In men, it does not directly supply testosterone; instead, it acts on the endocrine feedback loop.
●Mechanism: In males, androgens (like testosterone) can be converted to estrogen. When the brain senses high estrogen levels, it reduces the release of gonadotropins (LH and FSH), which in turn lowers the testicular production of testosterone. Tamoxifen blocks estrogen receptors in the brain (especially the hypothalamus/pituitary), interrupting this negative feedback. The brain then increases LH secretion, which stimulates Leydig cells in the testes to produce more testosterone.
●Clinical data:
○One study in healthy men found that taking tamoxifen (20 mg/day) for two weeks increased average testosterone levels by 52%.
○Another study comparing SERMs reported that tamoxifen raised testosterone by an average of 40% (compared to 25% with raloxifene).
○In men with idiopathic oligospermia (a cause of infertility), three months of tamoxifen therapy also showed significant testosterone elevation.
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