In this Feb. 13, 2020, file photo, The Official U.S. Government Medicare Handbook for 2020 over pages of a Department of Health and Human Services, Office of the Inspector General report, are shown in Washington. Credit: Wayne Partlow / AP

WASHINGTON — Medicare’s “Part B” outpatient premium will jump by $21.60 next year, one of the largest increases ever. Officials said Friday a new Alzheimer’s drug is responsible for about half of that.

The increase guarantees that health care costs will gobble up a big chunk of the recently announced Social Security cost-of-living allowance, a boost that had worked out to $92 a month for the average retired worker.

Medicare officials told reporters on Friday that about half the increase is attributable to contingency planning if the program has to cover Aduhelm, a new $56,000-a-year medication for Alzheimer’s disease. The drug would add to program costs because it’s administered in a doctor’s office and paid for under Medicare’s outpatient benefit.

The announcement on premiums comes as Congress is considering Democratic legislation that would curb what Medicare pays for medications.

The new Part B premium will be $170.10 a month.

Ricardo Alonso-Zaldivar, Associated Press