A method of calculating and correcting analyte levels in a first medium using measurements from a second medium, the method comprising: using a transceiver to calculate an initial second medium analyte level based on at least initial measurement data; using the transceiver to calculate an initial second medium analyte level rate of change based on at least the initial second medium analyte level and one or more past second medium analyte levels; using the transceiver to calculate a first medium analyte level based on at least the initial second medium analyte level and the initial second medium analyte level rate of change; using the transceiver to convey the first medium analyte level to a display device ; using the display device to receive and display the first medium analyte level; using the transceiver to calculate a subsequent second medium analyte level based on at least subsequent measurement data; using the transceiver to calculate an updated second medium analyte level rate of change based on at least the initial second medium analyte level, the subsequent second medium analyte level, and the one or more past second medium analyte levels; using the transceiver to calculate a corrected first medium analyte level based on at least the initial second medium analyte level and the updated second medium analyte level rate of change; using the transceiver to convey the corrected first medium analyte level to the display device; and using the display device to receive the corrected first medium analyte level and, after receiving the corrected first medium analyte level, display the corrected first medium analyte level instead of the first medium analyte level; wherein the display device displays the first medium analyte level until display device receives the corrected first medium analyte level. using a transceiver to calculate an initial second medium analyte level based on at least initial measurement data; using the transceiver to calculate an initial second medium analyte level rate of change based on at least the initial second medium analyte level and one or more past second medium analyte levels; using the transceiver to calculate a first medium analyte level based on at least the initial second medium analyte level and the initial second medium analyte level rate of change; using the transceiver to convey the first medium analyte level to a display device ; using the display device to receive and display the first medium analyte level; using the transceiver to calculate a subsequent second medium analyte level based on at least subsequent measurement data; using the transceiver to calculate an updated second medium analyte level rate of change based on at least the initial second medium analyte level, the subsequent second medium analyte level, and the one or more past second medium analyte levels; using the transceiver to calculate a corrected first medium analyte level based on at least the initial second medium analyte level and the updated second medium analyte level rate of change; using the transceiver to convey the corrected first medium analyte level to the display device; and using the display device to receive the corrected first medium analyte level and, after receiving the corrected first medium analyte level, display the corrected first medium analyte level instead of the first medium analyte level; wherein the display device displays the first medium analyte level until display device receives the corrected first medium analyte level. <EOS>