Walgreens, CVS and Walmart are limiting the number of at-home COVID-19 tests that customers can buy due to a recent surge in demand for the kits during the holidays.

CVS placed a limit of six test kits per purchase to deal with the increased demand and “ensure equitable access to tests both in store and digitally,” CVS spokeswoman Monica Prinzing told KTLA.

At-home COVID-19 tests available at U.S. pharmacies include Abbott BinaxNOW, Acon FlowFlex, Quidel Quickvue, Ellume and Pixel by LabCorp.

The kits let people test themselves and are available over the counter, without a prescription. Results are usually ready within minutes.

Customers hoping to nab one of the rapid at-home tests may find that the items are temporarily out of stock on CVS.com.

“We continue to work around the clock to provide our stores with inventory of the five over-the-counter at-home COVID-19 tests we offer,” Prinzing said.

Walmart also told KTLA that it is also seeing “significant demand” for home testing kits.

The retailer has “strong inventory levels nationally in store, however inventory is more limited online,” spokeswoman Tricia Moriarty said.

Customers can buy a maximum of eight testing kits online from Walmart, but nationally, there are no limits for in-store purchases of the rapid tests.

However, some locations may end up setting their own limits based on local inventory, Walmart said.

Walgreens also announced on Tuesday that it has seen an increase in demand for rapid over the counter COVID-19 tests and is setting a four-item purchase limit on the kits.

Walgreens said some of its stores may experience temporary shortages of the rapid tests.

The pharmacy said it is working with suppliers to make sure that customers have access to self-test kits through the holidays.

A representative for BinaxNow told the Los Angeles Times that there’s been “unprecedented demand” for the kits ahead of Christmas weekend, and the company is on track to make over 70 million tests a month in January.

The increased demand for at-home test kits comes as the U.S. sees COVID-19 infection numbers rise and grapples with the threat of the new omicron variant.

President Joe Biden on Tuesday announced the government will provide 500 million free rapid home-testing kits to Americans.

Shipments will begin in January, and people will be able to use a new website to order their tests, which will be mailed to them at no charge.