The Medicare Part B premium will increase $25 or from $109 to $134. Nationally, about 70% of the enrollees fall under the “hold harmless” rule designed to protect fixed-income seniors so their premiums can’t increase more than the Social Security COLA. Approximately half of these protected seniors will pay $134 in 2018 and the rest will get smaller-than-average Social Security increases resulting in a smaller premium jump to about $130. The other 30% are not covered by the hold harmless rule and experienced the increase to $134 or more last year. If their income is less than $85,000 single or $170,000 married filing jointly, they will continue to pay $134 a month in 2018.