Abstract: A single dosage dispenser for delivering chemical reagent to a test sample includes a body having an inlet and opposing outlet. The inlet is threadably and communicably engaged with a container holding a chemical reagent. The outlet includes a plurality of stepped receptacles for communicably receiving respective sizes of test sample holders. A spring actuated plunger is slidably mounted within the dispenser body between the inlet and the outlet. The plunger includes a reagent accommodating compartment. The spring urges the plunger into a first state wherein the plunger is communicably connected to the inlet for receiving a single dosage of reagent from the container. The user presses the plunger to drive the plunger within the dispenser body so that the compartment is communicably connected to the outlet. As a result, the reagent in the compartment is dispensed through the outlet into the test sample holder.