The Oklahoma Blood Institute has started testing all donors at selected drives to see how many have antibodies for COVID-19.
The information will go into research - and also help identify potential donors of the plasma used to treat the most serious COVID-19 patients.
OBI collected blood Thursday in a drive at Tulsa's Myers Duren Harley-Davidson, with antibody testing for all donors. That drive will continue Friday, and more drives this weekend will include the test.
"So, if anyone is wondering, if they were ill in the past or what's been going on, we'll get that antibody test and they'll get those results in the mail in about seven days" said Amanda Harden with OBI.
Donors are responding to the urgent need for blood, and the incentive of getting the antibody check, for free.
The test only detects antibodies, not active infection, and it's one of the tests the FDA fast tracked during the peak of the crisis - but which is not considered 100% reliable.
Donors are screened before they give to make sure they don't have Covid-19 symptoms.
For donors who do have the antibodies, OBI encourages them to sign up for plasma donations that can help patients who have the infection now.