A wearable drug delivery device has a needle assembly and a drug vial arranged side-by-side. This arrangement makes the device compact so that it can be easily worn around a user's wrist, for example. When the user triggers the device to inject a dose of medication like epinephrine, in an orchestrated sequence, a first spring drives the needle assembly downward and inserts a needle into the user while connecting the needle assembly to the drug vial. A second spring then delivers the dose from the drug vial through the needle and into the user. Advantageously, the small form factor encourages the user to wear the device and have lifesaving medication at the ready.