A method of predicting a blood glucose level of a user, comprising: obtaining, by an image capturing device, an iris image of the user； training a first convolutional neural network of a computing device using the iris image as an input to obtain a classification of the iris image； training a second convolutional neural network of the computing device using the classification and the iris image to extract an iris feature vector； and predicting, by the computing device, the blood glucose level of the user based on the iris feature vector.
