This systematic review examines the carbon footprint (CF) of healthcare systems, focusing on methodological transparency and results. The review included 15 studies that calculated and reported the CF of one or more healthcare systems. The mean ratio of healthcare system emissions to total national emissions was 4.9% (1.5%–9.8%), with CFs growing in most countries. Hospital care contributed the largest relative share of the total CF. At least 71% of the methodological items were reported by each study. The review highlights that healthcare systems significantly contribute to national carbon emissions, with hospitals being a major contributor. Mitigation measures can help reduce emissions over time. A checklist developed in this study can serve as a reference for future research to ensure methodological transparency and consistency in reporting results. The study used input–output (I–O) analysis to estimate sectoral CF, combining I–O data with environmental extensions. I–O models can be categorized into single-region (SRIO) and multi-region (MRIO) models. SRIO models are limited to domestic production and emissions, while MRIO models account for international trade and production differences. The choice between SRIO and MRIO models affects the level of uncertainty in CF calculations. The results showed that healthcare emissions varied by country, with some countries showing increasing CFs. The largest share of healthcare CFs came from hospitals, medical retail, and ambulatory services. Scope 3 emissions, which include indirect emissions from travel, pharmaceutical production, and medical equipment, accounted for the largest portion of healthcare CFs. The study found that most studies did not fully report their methodological choices, with only 75% of studies fulfilling all criteria. The transparency checklist developed in this study can help future research to ensure methodological consistency and transparency. The review also identified research gaps, including the need to assess the effects of emission reduction efforts on healthcare systems and the impact of different methodological choices on results. The study's findings suggest that healthcare systems contribute significantly to national carbon emissions, with hospitals being a major contributor. The results indicate that mitigation measures can help reduce emissions over time, and that future research should focus on improving methodological transparency and consistency in reporting results. The study also highlights the importance of sustainable transportation and green healthcare goods in reducing emissions in the healthcare sector.This systematic review examines the carbon footprint (CF) of healthcare systems, focusing on methodological transparency and results. The review included 15 studies that calculated and reported the CF of one or more healthcare systems. The mean ratio of healthcare system emissions to total national emissions was 4.9% (1.5%–9.8%), with CFs growing in most countries. Hospital care contributed the largest relative share of the total CF. At least 71% of the methodological items were reported by each study. The review highlights that healthcare systems significantly contribute to national carbon emissions, with hospitals being a major contributor. Mitigation measures can help reduce emissions over time. A checklist developed in this study can serve as a reference for future research to ensure methodological transparency and consistency in reporting results. The study used input–output (I–O) analysis to estimate sectoral CF, combining I–O data with environmental extensions. I–O models can be categorized into single-region (SRIO) and multi-region (MRIO) models. SRIO models are limited to domestic production and emissions, while MRIO models account for international trade and production differences. The choice between SRIO and MRIO models affects the level of uncertainty in CF calculations. The results showed that healthcare emissions varied by country, with some countries showing increasing CFs. The largest share of healthcare CFs came from hospitals, medical retail, and ambulatory services. Scope 3 emissions, which include indirect emissions from travel, pharmaceutical production, and medical equipment, accounted for the largest portion of healthcare CFs. The study found that most studies did not fully report their methodological choices, with only 75% of studies fulfilling all criteria. The transparency checklist developed in this study can help future research to ensure methodological consistency and transparency. The review also identified research gaps, including the need to assess the effects of emission reduction efforts on healthcare systems and the impact of different methodological choices on results. The study's findings suggest that healthcare systems contribute significantly to national carbon emissions, with hospitals being a major contributor. The results indicate that mitigation measures can help reduce emissions over time, and that future research should focus on improving methodological transparency and consistency in reporting results. The study also highlights the importance of sustainable transportation and green healthcare goods in reducing emissions in the healthcare sector.