A microneedle injection apparatus comprising: a housing having a base and a cavity that extends through the base to define an opening in the base, wherein the base of the housing is configured to be positioned toward a skin surface; a microneedle array comprising a first side comprising a plurality of microneedles; a microneedle array holder configured to hold the microneedle array and located in the housing, the microneedle array holder movable with respect to the opening in the base of the housing between a retracted position in which the microneedle array is recessed within the housing such that the microneedle array does not contact the skin surface when the apparatus is positioned on the skin surface and the microneedle array is coupled to the microneedle array holder, and an extended position in which at least a portion of the microneedle array is positioned to contact the skin surface via the opening when the apparatus is positioned on the skin surface and the microneedle array is coupled to the microneedle array holder; and a cover configured to be positioned to cover the opening in the base of the housing, the cover including a first portion configured to cover at least a portion of the base of the housing adjacent the opening, and a second portion configured to be received in the cavity of the housing and further configured to cover the plurality of microneedles on the microneedle array when the microneedle array holder is in the retracted position. a housing having a base and a cavity that extends through the base to define an opening in the base, wherein the base of the housing is configured to be positioned toward a skin surface; a microneedle array comprising a first side comprising a plurality of microneedles; a microneedle array holder configured to hold the microneedle array and located in the housing, the microneedle array holder movable with respect to the opening in the base of the housing between a retracted position in which the microneedle array is recessed within the housing such that the microneedle array does not contact the skin surface when the apparatus is positioned on the skin surface and the microneedle array is coupled to the microneedle array holder, and an extended position in which at least a portion of the microneedle array is positioned to contact the skin surface via the opening when the apparatus is positioned on the skin surface and the microneedle array is coupled to the microneedle array holder; and a retracted position in which the microneedle array is recessed within the housing such that the microneedle array does not contact the skin surface when the apparatus is positioned on the skin surface and the microneedle array is coupled to the microneedle array holder, and an extended position in which at least a portion of the microneedle array is positioned to contact the skin surface via the opening when the apparatus is positioned on the skin surface and the microneedle array is coupled to the microneedle array holder; and a cover configured to be positioned to cover the opening in the base of the housing, the cover including a first portion configured to cover at least a portion of the base of the housing adjacent the opening, and a second portion configured to be received in the cavity of the housing and further configured to cover the plurality of microneedles on the microneedle array when the microneedle array holder is in the retracted position. a first portion configured to cover at least a portion of the base of the housing adjacent the opening, and a second portion configured to be received in the cavity of the housing and further configured to cover the plurality of microneedles on the microneedle array when the microneedle array holder is in the retracted position.