Doctor and older man with walker (Photo: Thinkstock)

The number of retirees spending one-third to one-half of their Social Security benefits on health care costs rose significantly in 2018 and is likely to decline next year, but the respite will be only temporary.

According to a survey from The Senior Citizens League, 30% of the 1,161 retirees surveyed — most over 70 — are spending 35% to 50% of their Social Security benefits on health care, which includes Medicare Part B and Supplemental (Medigap) or Medicare Advantage coverage. In 2017, just 23% of retirees spent as much for roughly the same coverage.

(Related: Health Care Costs Eat Up Big Chunks of Social Security Benefits)

“The increase is due in large part to the effects of a zero and excessively low cost-of-living adjustment (COLA) in 2016 and 2017 … when Medicare premiums and out-of-pocket costs like prescription drugs were climbing steeply,” said Mary Johnson,  a Social Security and Medicare policy analyst at the league, in a statement. The Social Security COLA rose 0.3% in 2017 following no increase the previous year.

Johnson expects 2019 will be an improvement over 2018 in retirees’ health care cost burden, but only a short-lived one.

“There should be more retirees paying 11% to 33% of their Social Security benefits on health care and fewer paying 35% to 50% in 2019,” Johnson told ThinkAdvisor, noting that the 2019 COLA will more than cover the expected increase in health care coverage costs.

The Social Security COLA is expected to rise 2.9%, according to an updated outlook from The Senior Citizens League — marking the biggest jump in seven years — while the premium for Medicare Part B, which covers doctors and hospitals, is expected to rise by only $1.50, or 0.01%.

(Related: Social Security COLA Could Top 3% in 2019)

For the average Social Security recipient collecting $1,413 per month this year, benefits would increase to $1,455 per month next year and their Medicare Part B premium would total $135.50, leaving the average recipient with over $40 more in his or her pocket each month. Premium increases for Medicare Supplement insurance, aka Medigap, and for Medicare Advantage plans could eat up some of those extra funds, but but the biggest change is expected to come in 2020. That’s when two types of supplemental coverage — Medigap Plans C and F, which are the most comprehensive — will be discontinued for new enrollees.

The Medicare Access and CHIP Reauthorization Act of 2015 (MACRA), signed into law on April 16, 2015, eliminates the sale of Medicare Supplement Plans C and F to new Medicare enrollees on or after Jan. 1, 2020. Current enrollees in those accounts will be grandfathered.

Those two Medigap plans — there are 10 in total — cover the deductibles for Medicare Part B, which are estimated to increase to $185 in 2019 from $183 currently and to $193 in 2020. Medicare Supplement Part F also covers the difference between what a doctor or provider charges and what Medicare Part B will pay, commonly known as excess charges.

Current enrollees in Plan C or F will likely pay more for that coverage in the form of higher premiums.

Those beneficiaries could also choose a different Medicare Supplement plan, like Plan G, which started this year and covers excess doctor charges but not Medicare B premiums, or a Medicare Advantage plan, which also doesn’t cover Part B premiums.

— Check out How to Plan for Retiree Health Care Costs: The Advisor and the Quant on ThinkAdvisor.