Canadian Blood Services say 57,000 blood donation appointments across Canada must be filled before the end of August to ensure ready access to patients in need.
The agency says it needs 100,000 new donors to keep up with demand as it deals with a drop in donations in light of the pandemic.
The comments come as the agency defended its decision to suspend a mandatory masking policy.
Some longtime donors say they are now reconsidering whether to attend their next appointment out of concern they could contract COVID-19.