A system for generating an overdose risk score of a user includes a physiological sensor coupled to a wearable device and configured to detect attenuated light from a tissue site of the user and at least one hardware processor. The hardware processor can be configured to determine a plurality of parameters based on the attenuated light, determine a baseline risk, an instability index, an average slope, and desaturation pressure, and determine a weighted aggregate of the baseline risk, the instability index, the average slope, and the desaturation pressure for each of the plurality of parameters, determine an overdose risk score by determining a weighted aggregate of the plurality of parameters, determine an alarm level of a series of escalating alarm levels based on the overdose risk score, and implement intervention associated with the determined alarm level.