The New York Blood Center is declaring a blood emergency and is urging people to donate to “replenish the community’s critically low blood supply,” the nonprofit said Thursday.

“By spreading the word or even hosting your own blood drive, inviting friends, family, and community organizations, you may save lives,” said Andrea Cefarelli, the center’s executive director.

Cefarelli said the group is in “dire need” of O-negative blood with a reserve that is below a two-day supply.

“And that is just too low,” she said.

To maintain a safe blood supply, a seven-day inventory of all types must be continually replenished, the nonprofit said in a news release.

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Companies, organizations and community groups are encouraged to donate or host their own blood drives to help rebuild the blood stock.

O-negative donors are considered “universal,” and their blood type is needed most readily in trauma situations and emergency rooms, the release said.

Supplies of B-negative and A-negative types also have dropped to less than a two-day supply.

To donate blood or to find out about organizing a blood drive call 800-933-2566 or visit nybloodcenter.org.