Consumers are reaching deeper into their pockets to pay for groceries and gas. Last year, as many as half of all those who took out home equity loans used the money to help pay down their credit card debt, according to J. D. Power research. But home equity is no longer an easy source of financing. Month after month, cardholders keep falling behind on their bills.

“This downturn is the perfect storm where the consumer is getting squeezed from all levels,” said Michael Taiano, a credit card industry analyst at Sandler O’Neill. He projects that credit card loss rates for lenders, now around 5.7 percent, could go as high as 10 percent in next 18 months. That would be higher than the peak levels reached after the 2001 technology bust.

Since borrowers typically run up their balances before they stop paying, issuers have started cutting lines of credit. Often, lenders will lower customers’ credit limits as they pay down their debt  a technique known in the industry as “chasing the balance.” This way, they are on the hook for less money if borrowers default.

“They are trying to cut their risk exposure,” said Bill Ryan, an analyst at Portales Partners. “The consumer that used to use his house as an A.T.M. is now starting to use their credit card as an A.T.M.”

American Express is reducing credit lines for customers holding subprime mortgages and small-business customers in industries tied to the real estate market. And Chase Card Services, the consumer arm of JPMorgan, is taking similar action on distressed borrowers, especially in places like California, Arizona and Florida, where home prices have declined sharply.

Washington Mutual, HSBC, Target and Wells Fargo all acknowledged they were pulling in lines of credit as part of broader strategy of reducing risk.

None of those lenders, as a matter of policy, would comment on individual customer accounts.

Cardholders in places like Orange County in California, Atlanta and Phoenix have noticed their credit lines shriveling up.