This is a single center study. A total of 36 adult volunteers will be consented for the study. Volunteers will be admitted for an overnight stay. Half will be female and half male. Twelve volunteers will have a body mass index (BMI) less than 25 kg/m2, 12 will have a BMI 25-40 kg/m2, and 12 will have a BMI greater than 40 kg/m2. Volunteers will have height and weight measured after they have consented to participate. Exactly half the volunteers in each category will received a single dose of intravenous micafungin of 100 mg, while the other half will receive 300 mg as determined by a coin flip. The volunteers will have blood drawn via an intravenous catheter just prior to the dose, and then at 1, 4, 8, 12, 16, and 24h after the drug dose. The intravenous catheter is then removed after the 24h blood draw, and the volunteer discharged from the study. Compensation will be provided to the participants for their time.