Almost everyone in the UK will have benefited from the British National Formulary (BNF). It is used by medical professionals to safely prescribe medicines. First published in print in 1949 and updated regularly since, the vital medical resource needed to be reimagined for a digital age. The initial, ethnographic design research stage provided unprecedented insight into the working lives of medical professionals. This informed the design of a suite of user-centred medical information products, with the BNF transformed from a primarily paper format to a specialist app. Using human-centred design the app carefully considers the needs and workflows of clinicians. It’s updated each month and is very intuitive, enabling the user to quickly and accurately check drugs and drug interactions to maintain patient safety. The family of integrated digital and print products has been described as “indispensable”. Slashing the time it takes clinicians to prescribe drugs to patients, it is estimated that the app is saving 150,000 clinician hours across the NHS per month. The app is used to check a drug every three seconds and in the last year it has been used to safely prescribe drugs to over 15 million patients.