The climate crisis is no longer an abstract or distant problem, it is a health emergency that affects every facet of human life. From deadly heatwaves to the spread of infectious diseases and the displacement of populations, the health consequences of a rapidly warming planet are profound. Yet, the very institutions designed to protect public health are themselves significant contributors to the crisis. In the UK, the National Health Service (NHS) is one of the country’s largest carbon emitters, responsible for around 4% of total national greenhouse gas emissions. This makes it both a frontline responder to climate impacts and a key part of the problem, underscoring the urgent need for transformation not only in how healthcare is delivered but also in how it is conceived, funded, and held accountable in the context of planetary health.

This tension, between the NHS protecting public health and also contributing to environmental har, underscores the complex challenge of making healthcare truly sustainable. How can the NHS continue to deliver safe, accessible, and universal care while also achieving a radical reduction in its carbon emissions? And what trade-offs will be required in an already overstretched system, caught between spiralling demand, political neglect, and chronic underinvestment?

To its credit, the NHS has not ignored its role in the climate crisis. In October 2020, NHS England became the world’s first health system to commit to becoming net zero. Two targets were set: to reach net zero emissions for activities under its direct control (the “NHS Carbon Footprint”) by 2040, and to achieve net zero across its entire supply chain and services it commissions (the “NHS Carbon Footprint Plus”) by 2045. The Greener NHS programme was launched to drive this transformation. Its existence signals an important shift: that climate action is no longer considered outside the scope of healthcare but is now a foundational part of it.

But there is a vast difference between ambition and delivery. The NHS is a sprawling, highly complex system comprising over 200 trusts, thousands of GP practices, community health services, private contractors, and countless supply chains spanning the globe. Every pill, blood test, ambulance ride, surgical procedure, and hospital meal generates emissions. In fact, roughly 62% of the NHS’s total carbon footprint comes from its supply chain, everything from medical devices to pharmaceuticals, IT equipment to linen services. Clinical care itself, particularly in surgery and anaesthesia, is also a major contributor, with some anaesthetic gases having warming potentials thousands of times greater than CO₂. So far, progress has been mixed. The NHS has successfully phased out the most harmful anaesthetic gases such as desflurane and promoted the use of lower-carbon alternatives. It has also encouraged the shift from metered-dose inhalers, which use powerful hydrofluorocarbon propellants, to more environmentally friendly dry powder inhalers. Hospitals have begun retrofitting old buildings with more energy-efficient systems, and there has been a notable increase in digital services such as remote consultations, which reduce the need for travel. But these are the low-hanging fruits; important, yes, but insufficient in themselves.

The harder questions concern systemic change. Should NHS England (soon to be abolished and replaced with the Department of Health and Social Care alone) prioritise building entirely new, carbon-neutral facilities, or retrofit ageing hospitals despite limited financial resources? Can it meaningfully decarbonise without major new government investment, especially given current fiscal constraints and the economic fallout of more than a decade of austerity?

The capital costs of sustainability are significant. Energy-efficient building retrofits, green transport infrastructure, solar panel installations, and digital transformation all require upfront spending. A 2023 analysis by the Health Foundation estimated that decarbonising NHS estates could cost up to £15 billion. But delaying these investments may lead to far greater costs in future, in both financial and human terms. Not acting on climate change also has an economic toll. Poor air quality, for instance, is estimated to cost the UK economy over £20 billion annually through lost productivity and healthcare costs. Heat-related illness and flooding are already causing service disruptions and increasing demand for emergency care.

There are also risks in focusing too narrowly on emissions without considering equity. Policy decisions made in the name of sustainability can inadvertently worsen health inequalities if they are not carefully designed. For example, if certain services are centralised to reduce carbon output (fewer hospital sites, more virtual consultations) this might disadvantage rural populations, the elderly, or those without access to digital tools. Similarly, mandating low-carbon products from suppliers may raise costs or reduce availability of essential goods, disproportionately affecting small providers and the patients they serve. One proposed solution is to integrate environmental impact into health technology assessments. NICE (the National Institute for Health and Care Excellence) currently evaluates new treatments based on cost-effectiveness metrics such as QALYs (quality-adjusted life years). But what if carbon impact were included alongside clinical efficacy and cost? Such a shift would not only incentivise the development of greener drugs and devices, but also enable more holistic decision-making. However, it raises difficult ethical dilemmas: would we deny patients a highly effective treatment because its manufacturing process is carbon-intensive? Would this form of “climate rationing” be accepted by the public, or would it erode trust in an already strained system?

Supply chain reform also poses major challenges. The NHS Supplier Roadmap, launched in 2021, now requires all suppliers bidding for NHS contracts worth over £5 million annually to have a carbon reduction plan. By 2030, all suppliers will need to demonstrate progress toward net zero. This is a bold policy, but it risks consolidating procurement around large multinational corporations better equipped to navigate regulatory burdens. Smaller, local suppliers may struggle to comply, potentially undermining resilience, competition, and innovation. Some have proposed more radical structural shifts. Should the NHS, for instance, become a key player in a circular economy, reducing waste, reusing materials, and supporting local, sustainable production of medicines and equipment? What would it take to completely redesign clinical pathways to be both low-carbon and high-value, ensuring that “less is more” in medicine where appropriate? Over-prescribing and over-treatment are not only economically inefficient, they also carry a carbon cost. De-implementation science, which aims to identify and eliminate low-value care, should become a cornerstone of both clinical excellence and environmental stewardship.

Dietary reform is another untapped area. Hospitals serve millions of meals each year, many of which are meat-heavy and nutritionally subpar. Transitioning to plant-based catering could yield significant health and environmental benefits. Research shows that plant-based diets can reduce the carbon footprint of food by up to 73%. Yet such changes require careful consultation and culturally sensitive implementation to avoid backlash, especially in settings like mental health wards or long-stay units where food plays a key role in patient experience. Transport, too, must change. Ambulances, patient transport services, staff commuting, all contribute to emissions. Investment in electric fleets and incentives for low-carbon commuting are underway but remain limited. Meanwhile, staff burnout and chronic workforce shortages threaten the very capacity of the NHS to engage meaningfully in climate action. If sustainability measures are seen as extra burdens on an already exhausted workforce, they will fail. Frontline staff must be partners in this transition, not passive recipients of policy edicts.

Internationally, the NHS could play a leadership role. The UK has hosted key climate negotiations, including COP26, where the intersection of climate and health featured more prominently than ever before. The NHS has a unique platform from which to advocate for global action and support health systems in low- and middle-income countries to build climate resilience. Yet for that credibility to be sustained, it must lead by example at home. In the end, the question is not whether the NHS can afford to decarbonise; it is whether it can afford not to. The health of future generations depends on the choices made now. Climate change is already driving up demand, worsening population health, and stretching the system to its limits. Decarbonisation is not a luxury, it is an essential act of care. But it must be done wisely, justly, and transparently. There will be costs. There will be trade-offs. But if handled with courage and clarity, the transformation of the NHS into a sustainable, climate-conscious health system could become one of the great public service achievements of the century: a prescription not just for a healthier environment, but for a healthier society.