BackgroundBiotin is a commonly used supplement for hair, nail, and skin. Recent literature suggests that high-dose biotin therapy for neurological diseases like Multiple sclerosis can interfere with lab results that use biotin/streptavidin immunoassay, called biotin interference. Biotin interference can affect thyroid lab results, giving biochemical hyperthyroidism.Case presentationOur patient, a 64-year-old white man with a known history of multiple sclerosis, presented with elevated free T3, free T4, and low TSH that resembled hyperthyroidism. He had no symptoms of hyperthyroidism except some fatigue and tachycardia on the first encounter. He was started on anti-thyroid medications. He was then re-evaluated since his lab results remained the same after two months of anti-thyroid medications. It was found that he was on biotin, 10000mcg/day, for his multiple sclerosis. Biotin was discontinued, and five days later his lab results returned to normal values.ConclusionThe lack of knowledge of biotin use by patients can lead to misdiagnosis of patients’ thyroid lab results and improper management. Awareness about biotin interference and abnormal thyroid lab values should be a priority among clinicians and the public. If the biotin is discontinued on time, such misdiagnosis can be avoided.