The inserts form part of mailings that will be sent to regular donors at Christmas, Easter and during the summer holidays. These times have the biggest gap between supply and demand.
The executions are tailored to each season. For example, one features a National Blood Service logo on a flag that is sticking out of a sandcastle.
Another shows the same logo written in icing on the surface of a chocolate Easter egg.
The campaign was written by Simon Robinson and art directed by Maya Rowson.
Since Kitcatt Nohr won the account last November, it has produced a variety of work based on Delaney Lund Knox Warren & Partners' "do something amazing" campaign, which featured celebrities' testimonies about the service.