A non-powered device intended to be used by a healthcare provider to help safely administer a precise dose of medication from a (prefilled) syringe to a patient. It is in the form of a rod with volume graduations, secured alongside the syringe plunger, which includes a perpendicular sliding lock intended to mechanically obstruct the movement of the plunger into the syringe barrel beyond the desired volume mark, for safe medication administration. This is a single-use device.