Walmart and Sam's Club pharmacies will soon limit patients to no more than seven days' worth of opioids for certain prescriptions.
They'll also limit the strength of the opioids they provide.
A Walmart spokesperson said it's part of an effort to battle the opioid crisis.
Some states have their own laws limiting how many days' worth of opioids pharmacies can provide; Walmart says in those cases, its pharmacies will follow state regulations.
Doctors and pharmacies are strengthening opioid policies following a suggestion to do so by the Centers for Disease Control and Prevention in 2016.