Canada's blood supply is at a six-year low, prompting an urgent appeal for donors to roll up their sleeves.

Canadian Blood Services issued an appeal for donations Tuesday, particularly from people with blood types O and A. The organization said it will soon have less than three days' worth of inventory of major blood groups. The agency usually wants a five- to eight-day supply on hand.

"Without the help of Canadians we may have difficulty meeting the expected hospital demand across the country," CBS VP of donor relations Mark Donnison said in a statement, warning that, if the supply isn't replenished, some elective and routine procedures may be delayed.

CBS says the shortage is a result of recent "extremely low attendance" at donor clinics, combined with the constant demand for blood.

"This has created the lowest national blood inventory since 2008," according to CBS.

Donor Jason Henderson said news of the shortage prompted him to make an appointment.

“At some point, we all need an operation,” Henderson told CTV News, while donating in Richmond Hill, Ont. “I don’t know, it’s just the right thing to do.”

Another donor, Arlene Cress, said she made her appointment some time ago. Cress said she thinks it’s important to give blood consistently.

“Hopefully I will never have to need it, but a lot of people do,” she said. “And it’s an easy thing to do. So incredibly easy.”

Lorna Warwick, senior national director with the Leukemia & Lymphoma Society of Canada, is also calling on Canadians to donate to ensure the system can continue to help patients.

"While we are extremely concerned that the reduced availability of blood may result in delays in treatment for certain patients, we are confident in the work Canadian Blood Services is doing, in collaborating with healthcare authorities to ensure patient safety," she said in a statement.

Someone in Canada needs blood every minute of every day and CBS regularly collects 17,000 units of blood per week. The agency immediately needs 7,500 blood donations on top of the regular weekly totals to replenish the inventory.

First-time donor Linda Loprevite said she heard the callout via a commercial on the radio and decided to become one of those 7,500. “I just thought that I’m heathy and I’m well,” she said. “I figured that there’s no reason that I couldn’t donate, so, why not?”

For those interested in donating blood, CBS suggests making an appointment online, via its GiveBlood app, or by calling its toll-free hotline at 1-888-2-DONATE (1 888 236 6283).