In this paper, we investigate possibilities of glucose level monitoring in skin and blood within physiological range (0 - 500 mg/dl) by Monte Carlo simulations. The study was performed with a 3-layer plain phantom (5-mm thick) with optical properties of the layers taken from the literature. The superficial layer mimics the epidermis, the middle layer mimics the upper blood net dermis, and the deepest layer mimics the dermis of the skin. Diffuse reflected pulses from a pencil-beam laser source of 820 nm were registered by an array of coincident 0.3-mm thick rings with numerical apertures of 0.19. We show that for the used optical properties of the layers, the characteristics most sensitive to the variation of glucose level are the pulse energy and peak intensity for the source-detector separations of 1 to 3 mm. The relative change of these parameters is as high as 5-25%.