In certain embodiments, a method samples a body fluid of a patient. The method includes providing a fluid handling system having one or more fluid passageways. The method further includes infusing an infusion fluid by way of a fluid handling system into a patient through one or more fluid passageways. The method further includes obtaining a sample of body fluid by way of a fluid handling system from a patient through one or more fluid passageways. The obtained sample is no more than 400 microliters in volume. The method further includes analyzing at least an analyzed portion of the obtained sample by way of an analyte detection system operatively associated with the fluid handling system to determine a concentration of at least one analyte.