A pill dispenser for dispensing pills of various sizes includes a pill storage section, a dispensing section located at a lower end of the storage section, an optical sensor, a memory and a controller. The dispensing section includes a device for adjusting a variable size cavity configured to adjust to various pill sizes. The controller adjusts the variable size cavity of the dispensing section depending on the individual pill specifications, and determines if the optical sensor has sensed presence of the pill to be dispensed.