The Northern Ireland Blood Transfusion Service (NIBTS) is appealing for more blood donors in Derry to come forward after blood supply levels dropped over Christmas.
The service says the amount of blood it has stockpiled is low and, with just 6% of eligible donors in Northern Ireland actually giving blood, they are calling for more to come forward.
The NIBTS usually has enough blood donations to last five or six days but currently there is only enough stock for two or three days at the blood bank.
Three mobile units are used to gather supplies at around 250 locations and almost 1,000 donation sessions are held each year.
But Paul McElkerney, from the Northern Ireland Blood Transfusion Service, says at certain times of year more blood is used.
“Unfortunately, the spike came over the Christmas and New Year period,” he said. “This has left our stocks rather low and we would be worried about this.
“But with the public’s help, we would be able to get back into a very good position over the next week or so,” he added.
Jim McNair has been donating blood for more than 25 years.
He said: “It’s good to help others who might need blood, whatever their circumstances.”
Robert Carnochan also regularly attends donation sessions.
“It goes to children or, maybe, cancer patients - so you know you’re doing something,” he said.
Mr McElkerney says the service is hoping for between 700 to 1,000 people to come forward in the next couple of weeks to boost blood levels.
“If someone gives blood on Friday afternoon, by Sunday they will have saved a life,” he said.