1. A method comprising: obtaining a series of samples of at least one sensor signal that is responsive to a blood glucose level of a patient; determining, based at least partly on the series of samples, at least one metric assessing an underlying trend of a change in responsiveness of the at least one sensor signal to the blood glucose level of the patient over time; and assessing a reliability of the at least one sensor signal to respond to the blood glucose level of the patient based at least partly on the at least one metric assessing an underlying trend.