Switching to reusable cartridge insulin pens can reduce National Health Service costs while delivering environmental benefits

The climate crisis is a risk to health globally and reducing carbon emissions is a priority for the UK and other nations.¹ The NHS is the largest public sector contributor to England's national carbon footprint, accounting for 4% of England's total carbon footprint.² In response, the NHS committed to achieve net zero by 2045.² Within the NHS, pharmaceuticals account for an estimated 25% of emissions.² Despite pharmaceuticals' significant contributions, no national guidelines exist to help clinicians and patients make informed, sustainable decisions.

7% of England's population has been diagnosed with diabetes.³ Insulin is the only licenced medication for individuals with type 1 diabetes and is often needed to control glucose levels in individuals with type 2 diabetes.^{4, 5} Most of those administering insulin use an insulin pen, either a disposable pen that is fully replaced when insulin is exhausted, or a reusable cartridge pen that can last for several years. In the UK, Novo Nordisk and Sanofi currently offer recycling of their disposable insulin pens.^{6, 7} However, the number of disposable insulin pens returned for recycling is unclear. Current guidelines do not advise on the insulin delivery system clinicians should use. We aimed to assess the current number of disposable insulin pens prescribed in England compared to cartridge insulin (requiring a reusable cartridge pen) and compare differences in plastic waste, carbon footprint (CO₂eq) and prescribing cost to the NHS.

To compare the environmental impact of disposable and reusable insulin pens, we contacted all major manufacturers (Novo Nordisk, Eli Lilly and Company and Sanofi) of insulin in England for data on their products, including the quantity of plastic and life cycle assessments (LCA). Novo Nordisk provided plastic content data and LCA of their insulin products.^8-10 Sanofi provided data on plastic content only, therefore, carbon footprint could not be calculated. Eli Lilly and Company could not provide any data on their products, so only data on cost impacts are presented. LCA data provided by Novo Nordisk were calculated by adding the greenhouse gas contributions from the active pharmaceutical ingredient (API), device, cartridge and needle.^8-10 Plastic weight is presented in kilograms (kg) and LCA as CO₂ equivalent (CO₂eq). To assess the cost of disposable and reusable pens to England's National Health Service (NHS) we obtained NHS indicative prices (in pound sterling, £) of insulin products from the British National Formulary (BNF).¹¹ We used this information to calculate the cost, plastic waste and carbon footprint difference per prescription between disposable and the equivalent cartridge insulin. To quantify the current impact and potential savings of switching to cartridge insulin, we averaged the frequency of disposable insulin prescriptions from OpenPrescribing over 36 months (January 2021 to December 2023) in England to give an average annual prescription frequency.¹² We used average annual prescription frequency data to calculate the potential difference in annual plastic waste and carbon footprint between switching all disposable insulin prescriptions to cartridge insulin in England.

To compare the cost difference of switching everyone in England who currently uses a disposable insulin pen to cartridge insulin, we used the average annual disposable insulin prescriptions' frequency multiplied by the cost. The total average annual disposable insulin price was subtracted by the equivalent cost of cartridge insulin to give a difference for switching. Lastly, to calculate the additional cost of the reusable pen, we multiplied the current prescription frequency of reusable pens by their cost and added the total to the switching difference. All analysis of NHS cost is presented with and without accounting for replacing reusable insulin pens as the manufacturer often supplies the reusable pens free of charge. To explore the impact of the average total daily dose, which will influence both the cost and environmental impact of switching from disposable to reusable insulin pens, we calculated the environmental and cost impact of switching from disposable pens to cartridges based on average total daily doses of 20, 40 and 100 units. We averaged the cost, plastic waste and carbon footprint of the reusable cartridge pen over 3 years to analyse the total daily dose. We assumed pens were prescribed every 3 years based on manufacturer warranties.^13-15 Only disposable insulin pens with a cartridge pen equivalent were included in this analysis.

Over the 36 months from January 2021 to December 2023, 13,189,131 disposable insulin pens (72.5% (13,189,131/18,191,050) of total insulin prescriptions) were prescribed (total prescriptions cost to the NHS £28,614,282.75).

For Sanofi and Novo Nordisk products, 84–95% of plastic would be saved (annual average plastic saving 57.5 tonnes). Carbon footprint would be reduced by 40% for Novo Nordisk products (annual average carbon footprint saving 264.6 Mt CO₂e). The NHS cost of rapid-acting insulin cartridges is £0.32–0.46 cheaper per cartridge than the equivalent disposable insulin pen. By switching every disposable insulin prescription to an equivalent reusable cartridge insulin pen, based on average prescribing frequency between 2021 and 2023 as described above, calculated annual NHS insulin cost would be reduced by 5.4% (average annual total saving £1.57 million) without accounting for the cost of reusable pens and 2.6% (annual total saving £0.75 million) if average annual reusable insulin pen prescription rates are included.

By switching an individual using a total daily dose of 40 units of rapid-acting (NovoRapid™, Fiasp™ or TruRapi™) via a disposable insulin pen to the equivalent cartridge insulin, annual insulin cost would be reduced by £15.58–22.30 and plastic waste per patient would be reduced by 0.73–0.83 kg (Table 1). Assuming the NHS purchases the pen, this would take 0.63–0.83 years of use to become cost-neutral and average cost savings annually, with three yearly pen replacements, would be £7.25–13.35. Every individual that switched NovoRapid™ and Fiasp™ FlexTouch™ or FlexPen™ to Penfil™ would reduce the carbon footprint by 4.5 kgCO₂eq over the same period. Environmental benefits and cost reduction with reusable pens were substantially higher at higher insulin doses. However, costs for most insulin types were reduced even at a low total daily dose of 20 units (Table 1).

Our findings demonstrate that reusable cartridge insulin pens reduce plastic waste carbon footprint and are often cheaper than disposable insulin pens. Transitioning to reusable insulin pens as the default option could yield substantial benefits. Assuming that benefits are similar for manufacturers unable to provide information to those that do, the annual saving based on recent England NHS prescribing patterns would be 67.6 tonnes of plastic waste and 406.2 Mt CO₂e. For patients, cartridge insulin offers the advantage of taking less fridge space, and reusable pens include additional functions such as recording dose timing and connecting to bolus calculators. However, individual dexterity and patient choice should be considered when prescribing insulin pen type. A limitation of our results is that we did not include insulin pumps, which are increasingly used in individuals living with T1D. However, most individuals will continue to use insulin pens. Another limitation is that we could not compare the environmental impact of switching to biosimilar insulins, which are often cheaper. Switching to a more sustainable model of diabetes care has significant challenges. However, in this case, changes to prescribing behaviour are likely to result in meaningfully reduced costs while having clear environmental benefits.

In conclusion, this study highlights the pressing need to shift towards reusable cartridge insulin pens within the NHS, emphasising their benefits of cost-efficiency and environmental sustainability.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

None.