Right now, one of the hardest items to find on grocery shelves is one of the most important: baby formula. A shortage has sent families scrambling across the US, with the most vulnerable being hit hardest by lack of supply.

1. Why is there a shortage?

Long-term economic pressures collided with a sudden supply shock. The long-term issues stem from the pandemic, which disrupted supply chains and shipping of myriad products—including ingredients used in baby formula—and caused labor shortages that are vexing many industries. The supply shock ramped up in February, when Abbott Laboratories initiated a recall of powdered infant formula produced at its Sturgis, Michigan, facility, after receiving reports of bacteria infection in several babies.

2. How severe is the shortage?

For the week ending May 8, 43% of formula was out of stock at retailers nationwide, up from 31% about a month ago and around 11% in November, according to retail-tracking firm Datasembly. Companies including CVS, Target and Walgreens are limiting how much formula customers can buy.

3. Which baby formulas were recalled?

In February, the US Food and Drug Administration announced the recall of Similac PM 60/40, Abbott’s specialized low-mineral baby formula. That followed a report that an infant was infected with Cronobacter sakazakii after being exposed to the powdered formula, and eventually died. Earlier, Abbott recalled some Similac, EleCare and Alimentum formulas produced at its Sturgis facility. Those products were linked to cases of Cronobacter and salmonella infections. Cronobacter sakazakii infection can cause sepsis and meningitis, which can be deadly in newborns, according to the US Centers for Disease Control and Prevention.

4. Who is most affected and why?

Tennessee residents are facing the highest out-of-stock rates, while cities including Las Vegas, Houston and Charlotte are seeing lots of empty shelves, per Datasembly.

Low-income people are particularly struggling. Without much cash on hand, some families weren’t able to build up a stockpile and are dealing with price gouging from secondary sellers or having to pay for shipping from online retailers. In many states, Abbott Nutrition is the sole contractor for low-income families who get benefits through the Special Supplemental Nutrition Program for Women, Infants, and Children, known as WIC. That means parents shopping for formula have to take the extra step of contacting their local WIC office for alternatives or pay out of their own pocket.

5. Where can you find formula?

Families can contact their pediatricians, who may have samples or some supply. Parents can also check smaller retailers, like convenience stores or pharmacies that may have stock. Community resources like a local food pantry, milk bank or other non-profits may have access to supply nearby. It is safe for most infants to swap to other commercial brands, including generic ones, according to guidelines on navigating the shortage from the American Academy of Pediatrics.

You should not make your own formula using a recipe found online or elsewhere, according to the FDA and the AAP. Homemade formulas can be dangerous, leading to contamination and hypocalcemia, or low calcium, the FDA says. Doctors also advise against diluting formula to stretch it out. It can create nutritional imbalances and serious health problems, per the AAP. For babies older than 6 months, cow’s milk is an option “for a brief period of time” but the AAP cautions it “should not become routine” due to concerns infants won’t get enough iron.

6. Is breast-feeding an option?

For some people, of course. But formula is widely in demand by all sorts of families. Adoptive parents, moms with health conditions or limited breast milk supply, or babies with allergies are just some of the many who rely on formula. By six months, only a quarter of babies in the US are exclusively breastfed, according to CDC data. About 20% of breastfed infants were supplemented with infant formula in their first two days of life, per the CDC. Relactating—the process of starting to breastfeed again after a gap—can be time consuming and isn’t always successful.

Research shows that a lack of workplace resources, like a dedicated pumping space or enough breaks, can make a parent quit nursing earlier. The US is the only high-income country that doesn’t guarantee paid maternity leave, meaning many moms are back to work soon after welcoming a new addition to their families, leaving them little time to acclimate to nursing, too.

7. What’s the FDA doing about the baby formula shortage?

The US formula market is dominated by a handful of major suppliers, including Abbott. Due to FDA regulation, buying formula from other countries is largely out of the question for American consumers. The FDA will detail plans to expand imports of formula and “additional flexibilities” for domestic manufacturers and suppliers to get more formula on shelves, FDA Commissioner Robert Califf tweeted on May 13. The FDA is also working with other larger manufacturers that produce formula—Mead Johnson, Nestle, Danone and Perrigo—to boost supply.

8. When will the baby formula shortage end?

Abbott said on May 16 it reached a deal with regulators to reopen its Sturgis plant. It could resume production within two weeks after the FDA approval, but it will take six to eight weeks from the time the facility is reopened for products to reach shelves, Abbott said. President Joe Biden said on May 13 that he expected increased imports of baby formula to relieve the US shortage in a “matter of weeks or less.” The administration said it is offering manufacturers and retailers transportation and logistics support to improve the shortage as quickly as possible.