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.