PURPOSE: The development of subcutaneous (SC) formulations for monoclonal antibodies (mAbs), as an alternative to conventional intravenous (IV) infusion, represents a shift in health care delivery. The relative environmental impact of these two administration methods is not well understood. Minimizing the environmental footprint of health care is crucial due to its substantial contribution to greenhouse gas (GHG) emissions. This study compared the carbon footprint of SC and IV administration using pertuzumab/trastuzumab as a case example. METHODS: A Life Cycle Assessment was conducted to compare the environmental impacts of IV versus SC administration of pertuzumab/trastuzumab, focusing on climate change impacts expressed in carbon dioxide-equivalents (CO RESULTS: SC pertuzumab/trastuzumab resulted in slightly higher GHG emissions than IV administration, with 47.2 kg CO CONCLUSION: Both IV and SC administration routes of mAbs have substantial environmental impacts, dominated by mAb production emissions. This research provides a framework for assessing the environmental impact of health care technologies and underscores the importance of integrating environmental considerations into health technology assessments to mitigate the significant contribution of health care to global GHG emissions.