AlGaN/ GaN High Electron Mobility Transistors (HEMTS) were used to detect pH value and glucose concentration in the exhaled breath condensate (EBC). A Peltier element mounted on the backside of the AlGaN/GaN HEMT was used to lower the temperature of the sensor in order to condense the exhaled breath. The measured current change of the HEMT shows that the pH of the condensate from the exhaled breath is within the range of 7- 8, corresponding to the range of interest for human blood. The sensor exhibited a repeatable change of 1.24 mA/mm of the drain current at a drain bias of 0.25V, when the surface was exposed to repeated exhalations. ZnO nanorod-gated AlGaN/GaN HEMTs were used to detect glucose in EBC. A ZnO nanorod array was selectively grown on the gate area using low temperature hydrothermal decomposition to immobilize glucose oxidase (GOx).