Picture a retiree collecting $600 a month in Social Security. The 2026 COLA is 2.8%, so her check should grow by $16.80. But the Medicare Part B premium just rose $17.90, and both amounts flow through the same check. Do the arithmetic and you land somewhere dark: her benefit should shrink. When you ask whether the Medicare Part B premium can take your whole Social Security COLA, this is the exact fear underneath it.
The short answer is that it cannot take the whole thing for almost everyone, and a federal rule called "hold harmless" is why. But the longer answer matters more, because millions of people will still feel most of their raise disappear into premiums, and a small group will see their check sit perfectly flat. Let me walk through how it actually works.
So does Medicare Part B take your whole COLA?
For the average beneficiary, no. The average retired-worker benefit after the 2025 COLA was about $1,976 a month, and the 2.8% COLA for 2026 added roughly $56. The Part B premium rose from $185 to $202.90, a $17.90 jump. Subtract it and the average retiree keeps about $38 of the $56 raise. That stings, since the increase eats nearly a third of the COLA, but the check still goes up.
The math turns at the low end. Anyone collecting about $640 a month or less gets a COLA too small to cover the $17.90 premium increase. That is where the hold harmless provision steps in: it caps your Part B premium increase at the dollar amount of your COLA, so your Social Security check cannot be reduced by a premium hike. In 2026, roughly 1 million beneficiaries fall into that protected group. Their check stays flat instead of shrinking.
My honest take: the rule does its job, which is narrow. It stops your check from going backward. It does not stop the premium from swallowing the entire raise, which is what actually happens for those 1 million people. "Held harmless" sounds like a victory; in practice it means your raise evaporates the day it arrives.
Who actually qualifies for hold harmless
Four conditions, all of them required:
- You were entitled to Social Security benefits for November and December of the prior year.
- Your Medicare Part B premium is deducted from your Social Security benefit through November of the prior year into January.
- You do not pay higher Part B premiums because of IRMAA, the income-related surcharge that hits singles earning over $109,000 or couples over $218,000.
- Your COLA is not large enough to cover the full premium increase.
Miss any one of those and you pay the full $202.90. New Medicare enrollees get no protection at all, since they were not receiving benefits long enough to qualify. People who pay Part B directly, by check or online instead of through deduction, are out too. And higher earners on IRMAA never qualify. I think that last group is the part people underestimate: IRMAA can push Part B costs far above the base premium, and none of that surcharge is held harmless.
The one line item it protects, and all the ones it does not
Here is the part that catches people off guard every January. Hold harmless protects exactly one line of your Medicare bill: the Part B premium. That is it.
Part D prescription drug plan premiums, Medigap supplemental premiums, and the IRMAA surcharge itself sit completely outside the rule. None of them are capped by your COLA. Individual Part D plan premiums can rise by far more than your raise, and a 2022 law capping Part D base premium growth at 6% through 2029 applies to a national average used in a funding formula, not to what your specific plan charges you. Medigap premiums carry no federal growth cap at all.
So when you hear someone say their Social Security check went down despite the COLA, hold harmless was not the part that failed. The decline comes from the deductions the rule was never written to cover: Part D, Medigap, or other automatic deductions like Medicare Advantage premiums. Their benefit did not go down because of Part B. It went down because of everything else.
What this means for your 2026 check
Run your own numbers rather than relying on averages. Take your current benefit, multiply by 1.028, then subtract $202.90 instead of your old $185 premium. That is your January check, roughly, before Part D and anything else comes out. If you want to see how the COLA that produced that raise fits into fifty years of adjustments, this tool has the full history:
Open the free COLA history tool and CSV download
One habit worth starting this fall: when the COLA is announced each October, compare the percentage to the Part B announcement, which lands around the same time. That comparison, not the COLA headline alone, is what tells you how much of your raise you will actually spend.
Frequently asked questions
Can the Medicare Part B premium make my Social Security check go down?
Usually not. The hold harmless rule prevents a Part B premium increase from reducing your benefit below the prior year's level, provided you were entitled to benefits in November and December of the prior year, the premium is deducted from your check, and you do not pay IRMAA.
How much did the Part B premium rise in 2026?
It rose $17.90 per month, from $185 to $202.90. That is smaller than the dollar value of the 2.8% COLA for anyone receiving roughly $640 or more per month.
Who is not protected by hold harmless?
New Medicare enrollees, people who do not have Part B deducted from Social Security, higher earners paying IRMAA, anyone whose COLA fully covers the premium hike, and anyone paying Part B directly rather than through deduction.
Does hold harmless cover Part D or Medigap premiums?
No. Only the Part B premium is capped. Part D drug plan premiums, Medigap premiums, and IRMAA surcharges can all rise faster than your COLA.
What is the average Social Security benefit after the 2026 COLA?
About $2,031 per month for retired workers, up roughly $56 from $1,976. The $17.90 Part B increase consumes about a third of that average raise.
Sources: Medicare Interactive, "Increases in Part B premiums and the hold harmless provision"; Nolo, "What Is Social Security's Hold Harmless Rule?"; The Motley Fool, "The 2026 Social Security COLA Gave Retirees $56 a Month, and Medicare Took Most of It Back." Figures verified October 2026.