You can buy adrenaline (epinephrine) online for medical use, such as for emergency allergy treatment (anaphylaxis), but it from a licensed medical provider in the U.S.. Adrenaline is classified as a "Prescription Only Medicine" (POM), so you cannot buy it over-the-counter (OTC).

To get a prescription, you must have a medical evaluation to determine if adrenaline is safe and appropriate for you.

Once you have a prescription, you can fulfill it at major online or retail pharmacies. Online Epipen Prescriptions - Sesame