A portable therapeutic fluid dispensing device comprising: a reusable part comprising a reusable part housing including at least a controller and a first portion of a driving mechanism ; and a disposable part comprising a disposable part housing including at least a reservoir to retain therapeutic fluid, an outlet port to which the therapeutic fluid is dispensed, a fluid conduit providing fluid communication between the reservoir and the outlet port , and a second portion of the driving mechanism ; wherein at least a portion of the disposable part housing defines at least a portion of the reservoir ; wherein the second portion of the driving mechanism is mechanically couplable to the first portion of the driving mechanism upon connection of the disposable part to the reusable part ; and wherein the reusable part further comprises: a mechanism to monitor fluid levels inside the reservoir, the mechanism comprising a fluid level sensor ; characterized in that the fluid level sensor comprises: at least one energy source ; at least one energy detector to detect energy emitted by the at least one energy source , the at least one energy detector further configured to generate a signal to be processed by a processor; and a regulator to regulate the level of energy received by the at least one energy detector based, at least in part, on the fluid level in the container . a reusable part comprising a reusable part housing including at least a controller and a first portion of a driving mechanism ; and a disposable part comprising a disposable part housing including at least a reservoir to retain therapeutic fluid, an outlet port to which the therapeutic fluid is dispensed, a fluid conduit providing fluid communication between the reservoir and the outlet port , and a second portion of the driving mechanism ; wherein at least a portion of the disposable part housing defines at least a portion of the reservoir ; wherein the second portion of the driving mechanism is mechanically couplable to the first portion of the driving mechanism upon connection of the disposable part to the reusable part ; and wherein the reusable part further comprises: a mechanism to monitor fluid levels inside the reservoir, the mechanism comprising a fluid level sensor ; characterized in that the fluid level sensor comprises: at least one energy source ; at least one energy detector to detect energy emitted by the at least one energy source , the at least one energy detector further configured to generate a signal to be processed by a processor; and a regulator to regulate the level of energy received by the at least one energy detector based, at least in part, on the fluid level in the container . a mechanism to monitor fluid levels inside the reservoir, the mechanism comprising a fluid level sensor ; characterized in that the fluid level sensor comprises: at least one energy source ; at least one energy detector to detect energy emitted by the at least one energy source , the at least one energy detector further configured to generate a signal to be processed by a processor; and a regulator to regulate the level of energy received by the at least one energy detector based, at least in part, on the fluid level in the container . at least one energy source ; at least one energy detector to detect energy emitted by the at least one energy source , the at least one energy detector further configured to generate a signal to be processed by a processor; and a regulator to regulate the level of energy received by the at least one energy detector based, at least in part, on the fluid level in the container . <EOS>