Calgary's about to get another blood clinic during a period of 'critical need' for the national donation collection agency.

"The need for blood is ongoing. Every minute of every day, someone requires blood," Susan Matsumoto of Canadian Blood Services (CBS) said.

"We are at a critical need for blood actually right now."

The new Eau Claire Market clinic is set to open July 10 for blood donations and July 11 for plasma.

Donors joined CBS employees and volunteers Wednesday for a tour of the clinic and to create a human blood drop photo.

Matsumoto says there is a gap between what's coming in and what is needed for an optimal supply.

"Our national inventory ranges between 11,000 to 14,000 [units of blood] a day," she said.

"A healthy, strong range is between 20,000 and 25,000. Our O-negative blood type, the universal blood type, is really low as well. We are down to less than a three-day supply on hand and it should be in the five- to eight-day range."

She says CBS is trying to make donating easy.

"You can book your appointment online now at blood.ca or download the give blood app. If you book your appointment online in advance, we can also send you the blood questionnaire in advance. The process takes about an hour, but at times we can get people through much faster, in about 45 minutes.

"You just have to be 17 years of age, in good health, well hydrated and then come on in."

National Blood Donor Week runs until June 19.