A method and system are described for detecting a hypoglycaemic state in a patient. The patient's heart rate is monitored (102) to provide a heart-rate signal. A time-lagged signal is determined (106) as the difference between the heart-rate signal and a time-lagged version of the heart rate-signal. The heart-rate signal is filtered with a low-pass filter (110, 120) to provide a heart-rate trend. An absolute difference between the heart-rate signal and the heart-rate trend is determined (112,122) to provide an absolute-difference signal. A second time-lagged signal is determined (116, 126) as a difference between the absolute-difference signal and a time-lagged version of the absolute-difference signal. The occurrence of a hypoglycaemic condition is inferred (130, 132) dependent on the time-lagged signal and the second time-lagged signal.
