Canadian Blood Services is urging Canadians to make a donation as the country's blood supply is "critically low."

Fewer donations over the past few months have created the lowest blood supply since 2008. All blood types are required, but especially types A and O. 

The blood agency would like to have a five- to eight-day supply of blood on hold. Currently, the supply is down to three days.

Canadian Blood Services is worried it won't be able to meet hospital orders, which could result in elective surgeries being postponed or cancelled, said spokeswoman Susan Matsumoto.

The main reason for the low inventory is donors simply not showing up for appointments, she said. 

"I think if you make an appointment, it's a commitment and you need to be there," said Christina Hadden, who has given blood 98 times.

To meet hospital demands, Canadian Blood Services regularly collects 17,000 units of blood per week.