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Immunoassay interferences, including those from exogenous substances like biotin, can lead to misinterpretation of laboratory results and clinical decision-making challenges. A 28-year-old unmarried female presented to dermatologist with 4-year history of acne, hirsutism, and hair loss. Hormonal assays using chemiluminescence immunoassays (CLIA) and enzyme-linked immunosorbent assays (ELISA) revealed alarmingly high testosterone levels, suggesting neoplastic androgen excess and severe insulin resistance. This prompted referral to endocrinology for further evaluation. Patient's menarche occurred at age 11, with regular menstrual cycles. Family history indicated diabetes and hirsutism, but not infertility. Physical examination revealed body mass index (BMI) of 21.8 kg/m2 and Ferriman-Gallwey score of 11. Despite severe biochemical hyperandrogenism, her clinical presentation was mild. Differential diagnoses included polycystic ovary syndrome (PCOS) and late-onset congenital adrenal hyperplasia (CAH). Repeat hormonal testing, performed at multiple laboratories using liquid chromatography-mass spectrometry (LCMS), CLIA, and ELISA, showed normal testosterone, free testosterone, and insulin levels, suggesting that the initial results were falsely elevated. Review of her dermatology prescriptions revealed that she had taken a single 10 mg tablet of biotin 33 hours before first blood draw, leading to diagnosis of biotin interference in immunoassays. After the two-week biotin washout period, her subsequent endocrinology work-up had indicated “normalized” hormonal levels. Pelvic and abdominal ultrasound imaging revealed normal ovaries and adrenal areas. Thus, biotin associated testosterone (and insulin) immunoassay interference can confound clinical diagnosis and management. Any observed discordance between clinical symptoms, signs and hormonal levels should raise possibility of immunoassay interferences, reemphasizing need for heightened physician awareness.