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A significant dip in donors and an uptick in summertime motor vehicle accidents and trauma are taking a toll on the blood supply in Chicago and across the country.

Officials say this is common around this time of year after the Independence Day holiday.

But Lifesource, which is one of the largest blood suppliers in Illinois, says this shortage is the worst they've ever seen.

Lifesource is urging donors of all types to come in. But they're particularly looking for donors with the universal types O Negative and O Positive.

Donating takes about an hour.

And all week Lifesource donor center will keep extended hours to accommodate walk ins.

Visit LifeSource.org or call (877) 543-3768 to schedule an appointment to donate.

From Monday, July 10th through Sunday, July 16th, all LifeSource community donor centers will be open extended hours to accommodate more donors.

Visit http://www.lifesource.org/donate-blood/where-to-donate/ to find your nearest donor center or a mobile blood drive happening near you.

Walk-ins are welcome at any LifeSource location.