A biosensor detects a medication applied to an upper epidermal layer of skin of a user. The biosensor obtains at periodic intervals a concentration level of the medication in the upper epidermal layer of skin and surrounding tissue of the user. The biosensor may also detect the concentration level of the medication in an arterial blood flow of the patient or obtain a concentration level of a substance in the arterial blood flow, wherein the concentration level of the substance correlates to a first concentration level of the medication. The biosensor may determine an absorption rate of the medication in the upper epidermal layer of skin and surrounding tissue and in an arterial blood flow of the patient from the detected concentration levels of the medication obtained at the periodic intervals.
