Diabetics and insulin suppliers are increasing their stocks of insulin. They're worried about new supplies not arriving on time if Britain leaves the European Union without a deal.

David Burns is a 37 year old teacher. He lives in London. David is one of 3.7 million diabetics in the UK who rely on insulin. It controls their blood sugar levels.

David: "All of these come from Switzerland, these come from Denmark, but we don't make any of this here and none of these companies that made this are British - I think the vast majority of them are Swiss."

A no deal Brexit will mean replacing customs agreements and health controls. This could delay drugs travelling across the border. Patients' lives may be in danger.

The Department of Health says it has plans ready if there are delays at the border. It will fast-track emergency medicine deliveries by sea and by air. But David is still worried.

David: "If I ran out of insulin, obviously I don't want to test this out, but I can't imagine I'd have more than a couple of months left on this planet, so I'm terrified of a no-deal Brexit."