To estimate condition-specific patient travel distances and associated carbon emissions across common chronic diseases in routine National Health Service (NHS) care, and to assess the potential carbon savings of modal shifts in transportation.

Retrospective population-based cohort study.

NHS Greater Glasgow and Clyde, Scotland.

6599 patients aged 50–55 years at diagnosis, including cardiovascular disease (n=1711), epilepsy (n=1044), cancer (n=716), rheumatoid arthritis (RA; n=172) and a matched control group based on age, sex and area-level deprivation (n=2956).

Annual home-to-clinic distances and associated carbon emissions modelled under four transport modes (petrol car, electric car, bus, train) across five time points: 2-year prediagnosis, diagnosis year and 2-year postdiagnosis.

Mean annual travel distances to hospital varied by condition and peaked at diagnosis. Patients with cancer had the highest travel distances (161 km/patient/year for men; 139 km/patient/year for women), followed by RA (approximately 78 km/patient/year). The matched control group travelled 2/patient/year to 8.0 kg CO₂/patient/year. Bus travel resulted in intermediate emissions, estimated between 10.5 and 8.0 kg CO₂/patient. When travel was modelled using electric vehicles, emissions dropped between 3.5 and 2.7 kg for all conditions. Train travel produced similarly low emissions. Reducing petrol car travel from 100% to 60% lowered emissions up to 6.6 kg CO₂/patient.

Condition-specific estimates of healthcare-related travel emissions provide baseline understanding of the opportunities and challenges for decarbonising healthcare. Emission reduction is most achievable through modal shift, yet such shifts depend on factors beyond NHS control—such as transport infrastructure, digital access and social equity. Multisectoral strategies, including targeted telemedicine and integrated transport and urban planning, are critical to achieving net-zero healthcare while maintaining equitable access to care.