Climate change is a major threat to global health, and healthcare is itself a substantial contributor. Choosing the route of drug administration may represent a simple opportunity to reduce environmental impact without compromising care.

To quantify and compare the incremental environmental impacts and projected future health losses associated with oral, intravenous (IV), and intramuscular (IM) drug administration.

We performed a life cycle assessment of route-specific materials and packaging associated with oral and parenteral administration scenarios in the emergency departments of the public hospitals of Marseille, France. The functional unit was administration of 100 mg ketoprofen. The active pharmaceutical ingredient was excluded to isolate the environmental impact attributable to the administration route. Environmental impacts were assessed using ReCiPe 2016 and converted into disability-adjusted life minutes (DALMs).

GHG emissions were: 19 g CO₂e for oral administration, 279 g CO₂e for IM injection, 440 and 521 g CO₂e for IV flash and IV syringe pump administration with a pre-existing catheter respectively, and 776 g CO₂e for IV administration requiring catheter placement. Oral administration also had the lowest impact across all 18 midpoint environmental indicators. Projected health losses ranged from 0.13 to 5.59 DALMs, with climate change accounting for 88–92% of the total impact.

When clinically appropriate, prioritizing oral administration and reducing unnecessary IV use may substantially decrease healthcare-related emissions while maintaining quality of care, representing a simple step toward more sustainable healthcare and contributing to health for future generations.