Give blood, get free Mets tickets!

It seemed like a nice little promotion until the Mets jumped into the division lead and tickets got so hot that New York Blood Center says it can't acquire enough of them to fulfill its end of the bargain.

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Donors who hadn't already been issued tickets will have to wait until 2016 to receive their reward, the Blood Center told participants in an email on Friday.

"As you likely know, the Mets have enjoyed an amazingly good season and the demand for tickets has increased sharply," the email said. "Unfortunately, we are now unable to purchase the volume of tickets that we need to fulfill our pledge to you and other donors."

There's a direct correlation between promotional events and donor participation, according to an NYBC employee who was fielding calls from upset donors.

To make up for the unexpected issue, the NYBC is promising its donors tickets to a game during the 2016 season. As for 2015, "It's out of our hands," said the NYBC employee said.