The first ones will be sent out this week by the NHS to identify 5,000 with the “universal donor” type that can be given to almost anyone.
It is the first-ever mass testing of its kind and will involve 30,000. The kit allows a few small drops of blood to be extracted.
A litmus-test style card and a chart allow identification of blood type within five minutes.
Those found to have O negative will be offered priority appointments to help ensure they become long-term donors and boost stocks for the winter and beyond.
Health Minister Neil O’Brien said: “This innovative pilot scheme means that donors can easily and conveniently book in and donate, ensuring that the NHS can remain stocked with the blood it needs to save lives and be more resilient in future.”