A portable auto-injector configured to store a dry medication separately from a liquid component, wherein removal of a cap operates a first actuation mechanism which opens a valve between a first and second chamber that are slidably movable relative to each other and thus allows for the initiation of a mixing step prior to injection. An extendable needle guard is provided over the delivery assembly which prevents premature injection as well as inadvertent sticks or other cross contamination of a needle. The needle guard can also form part of a secondary trigger mechanism which injects the mixed components after the mixing stage is complete.