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HOUSTON– Donating blood is an act of kindness towards your man, but did you know it had a shelf life?

That’s right, every bag of blood has an expiration date and it doesn’t last as long as you would think.

“Blood does expire after 42 days,” said Joshua Buckley of the Gulf Coast Regional Blood Center.

So, what happens to the old blood?

“They will ship it to either Tulsa, Oklahoma or Dallas where it will be incinerated and destroyed,” said Tyler Moyer, American Red Cross.

Luckily, Houstonians have nothing to fear.

Home to the largest medical center in the world, Houston is in no short supply.

In fact, blood is like a paycheck in the Bayou City.

It’s spent before it’s even given.

“We don’t usually run into that problem because we need 1,000 donations a day in order to meet the need of the 170 healthcare facilities that we service, so that’s why it’s really important for people to come in on a regular basis, not just when there’s a mobile set up at their church or place of work,” said Buckley.

Not every city is a medical hub like Houston so your donations could help people all over the country.

“With the Orlando nightclub shooting, with the shootings of the police in Dallas, even with the flooding we had in Louisiana, we donated blood. They needed it at the time when that much blood is taken off the shelves if there’s another disaster and the blood’s not there, that’s a serious issue,” said Buckley.

Because blood doesn’t last, giving several times a year can make a huge difference.

“One donation, just an hour of your time, could save up to three lives. What else can you do for an hour in a day where you get to be a real-life hero?” said Buckley.

What about synthetic blood?

Medical technology continues to make amazing advances as scientists at the University of Bristol in the UK recently made major breakthroughs in substitute blood research.

Don’t get too excited, though. These technological advances are still in the works.

So, as of now, there’s no replacement for what is flowing through your veins.