Luke Halcro said he was a little nervous about donating blood for the first time.

"The unknown aspect was a little bit daunting, not not knowing how I was going to feel afterwards ... but I was just happy to help," he said.

Luke Halcro donated blood for the first time this month.

Mr Halcro's first-time donation came as the Australian Red Cross Blood Service launched an appeal for people with O-Negative and O-Positive blood types to give, as the national supply dwindles to just two days' worth of donated blood.

Red Cross Blood Service spokesman Shaun Inguanzo said they needed 8000 donors to help in the two weeks between May 22 and June 2 to avoid a shortage that historically coincided with the winter flu season.