People with prescriptions to fill could run into an unexpected snag over the next couple of days, as hundreds of pharmacists may call out of work to protest working conditions at CVS and Walgreens.

Organizers of the “Pharmageddon” protest told NBC News that around 900 people in as many as 10 states could participate in the ongoing protest, which started Monday and will end Wednesday. There was no way to independently verify that number.

Lannie Duong, a clinical pharmacist based in California, is one of the key organizers of the protests. She said that, along with sickouts and walkouts, members have discussed protesting at the corporate headquarters of Walgreens and CVS, which are in Deerfield, Illinois, and Woonsocket, Rhode Island, respectively. Those protests are scheduled for Wednesday.

The protests are that much more notable because the pharmacists don’t have a union and aren’t asking for better pay. They primarily want their employers to hire more staff to alleviate the workload and to eliminate policies that push them to work faster. They say those conditions are making it more likely they will make a mistake that could harm a patient.