Disclosed are methods and apparatuses for determining analyte concentration in a sample such as bodily fluid. Systems and methods disclosed herein can also include a treatment dosing system to infuse or inject a treatment dose (e.g. insulin, dextrose, etc.) and provide glycemic control. The dose of the treatment drug may be based on the patient's calculated sensitivity to treatment dosing, for example. The dose of the treatment drug may be based on the concentration of the analyte or the average value for the concentration of the analyte and/or the rate of change of the value of the concentration of the analyte. Delivery of the treatment drug can be cut off if the determined analyte concentration indicates that continued delivery would be harmful to the patient.