WASHINGTON — Medicare monthly premiums for doctor visits and outpatient care will jump next year from $78.20 to $88.50, federal officials said yesterday.

The 13.2 percent increase in premiums for Medicare Part B is lower than last year's record-high 17.4 percent spike but nevertheless drains more cash from the Social Security checks of Americans 65 or older, from which Medicare premiums typically are drawn. The average Social Security benefit is $955 a month.

The premium increase will offset higher program spending that's due to more intensive patient care, said Herb Kuhn, director of the Center for Medicare Management at the Centers for Medicare & Medicaid Services. Included in that spending is more-frequent use of hospital outpatient services, doctor visits, lab tests, imaging and other minor medical procedures.

The higher premiums also will help shore up Medicare's Supplementary Medical Insurance trust fund, which pays a portion of physician and outpatient care. Legislation Congress passed in recent years to increase what Medicare pays for physician services has left trust-fund assets "below where we would normally like it to be," said Richard Foster, Medicare's chief actuary.

If Congress increases the physician-payment level this year, Medicare's 2007 premiums for doctor services probably will increase, Foster said.

Kuhn said doctors should be adequately compensated for treating Medicare's 43 million elderly and disabled patients.

But he added that "the current system right now is just not sustainable."

The increase in hospital and physician costs comes at a time senior citizens will be deciding whether to pay an additional premium to enroll in a new Medicare drug benefit that starts Jan. 1. Last month, President Bush promoted drug premiums of $20 or less that will be available, although the average for the benefit may be about $32 a month.

Medicare is facing rising health-care costs, increased use of services, a growing number of beneficiaries and a dwindling tax base. When that's coupled with the new prescription-drug benefit, Kuhn said, Medicare's price tag is "a cause of some major concern."

The Part B premium, which helps pay for physician services, hospital outpatient care, durable medical equipment and other services, will be only slightly higher than the $87.70 Medicare officials had predicted in the Medicare Trustees' Report earlier this year. More than 90 percent of Medicare beneficiaries are enrolled in Part B, which is voluntary.

Medicare premiums are updated annually under a formula set by statute. The law requires that Part B premiums cover 25 percent of the program's costs. The federal government pays 75 percent.

Medicare's Part A deductible, which mainly covers inpatient and skilled nursing-facility care and is paid by patients when they're admitted to hospitals, goes from $912 this year to $952 next year.

Material from Bloomberg News is included in this report.