Abstract: The present invention includes a method and device for warning of hypoglycaemic attacks, which is a big problem for especially diabetics, who are in insulin treatment. It is estimated that about 1 million people have a decreased quality of life as a result of hypoglycaemic attacks. The invention collects EEG signals from people, who must be supervised and analyses these in order to detect characteristic changes in the EEG signals, which occurs in advance of a hypoglycaemic attack. In a preferred embodiment the EEG signals are collected with subcutaneously placed electrodes and the signals are lead via wires drawn under the person's skin to a similar subcutaneously placed signal processing unit. The signal processing analyses the EEG signals and when the pre-seizure characteristics signal changes are detected, a warning signal is given to the person from an alarm giver build into the signal processing unit, e.g. in form of a vibrator.