Abstract: A fluid reservoir and administration device for delivering a dosage of a medicament to a patient. The device has a base unit attachable to the skin, a reservoir unit attachable to the base unit, and a cap unit attachable to the reservoir unit. The base unit has a latching member, and a needle. The reservoir unit has a fluid filled cavity, a ratcheting element, a threaded member, and a plunger for forcing the fluid through the needle. The cap unit has ratcheting teeth engagable with the ratcheting member, and a threaded post engagable with the threaded member of the reservoir unit. When the cap unit is rotated, the threaded post is advanced toward the plunger which forces a metered dosage of the fluid through the needle and to the patient. The ratcheting member allows the cap unit to rotate in a single direction, thereby preventing a vacuum in the cavity.