Supermarkets will start using government data to identify at-risk individuals and provide them with the supplies during the coronavirus outbreak.
Across the UK 1.5 million vulnerable people are isolating for 12 weeks in an attempt to slow the spread of Covid-19.
Retailers have been forced to adapt to ensure those unable to leave the house can get the provisions they need.
It has not yet been made clear what criteria will be in place to ensure that supplies get to the right people, but supermarkets have said they will start contacting them from the start of next week.
Supermarket Sainsbury's has confirmed it is working with Government data to prioritise delivery slots for those most at risk.
While Asda said it has a "dedicated team" working with the Government and "fellow supermarkets to ensure those people who have been identified as highly vulnerable get what they need".
The retailer has also introduced contactless drop-offs for home delivery customers.
Tesco has limited its online shoppers to a maximum of 80 items per order in a bid to "get more orders on to each van".
Elsewhere, Richard Walker - managing director of Iceland - said the company had "done their best" to restrict online delivery orders to the most vulnerable, but admitted new slots are being "quickly snapped up".
Speaking on BBC Radio 4's Today programme, Mr Walker urged healthy people to go against the Government's advice and visit shops in person to free up delivery slots because "current demand vastly exceeds supply".
Tesco issued a similar call, in a statement a spokesman for the supermarket said: "We ask those who are able to safely come to stores to do so, instead of shopping online, so that we can start to free up more slots for the more vulnerable".
Iceland boss Mr Walker said: "I'd actually urge the opposite of the PM, in that, if you are healthy, not in a vulnerable category and adhere to social distancing guidelines, please do shop in store.
The Iceland boss added: "That will enhance priority online for those who need it most."
A number of retailers have seen similar unprecedented demand for online delivery shopping. On Friday morning, customers faced a 20 minute wait to access the Morrisons online shopping service.
The website queuing system showed 24,256 people were waiting to access the site.
Defra said by combining Government and supermarket data, it could "ensure essential items are delivered as soon as possible to the people with medical conditions that make them most vulnerable".
Alongside the measures taken by retailers, Defra said it had advised local authorities "to allow extended delivery hours to supermarkets" so shelves can be restocked more quickly.
The government has said that going out to shop for essential items like food is acceptable but to limit this to once a week if possible. Please practice social distancing whilst shopping and wash your hands!
Photo credit: PA