More than one million people in England paid more than they needed to for prescriptions in the year to April 2021, according to MoneySavingExpert.com.
On average, they missed out on savings of around £40 – because a certificate could have capped their costs.
MoneySavingExpert said people can buy an NHS prescription “season ticket” which would enable them to save money typically if they tend to pay for more than one prescription per month.