It will cost a lot since you will no longer have an employer picking up some of your costs. But you might qualify for some government subsidies through the Affordable Care Act. The exact amount can vary quite a bit depending several factors.
Medicare does kick in once you are 65, but there are costs for that coverage, too. And many retirees choose to buy so-called Medigap policies that provide coverage above and beyond what is offered through Medicare, or Medicare Part D prescription drug coverage.
Add it all up, and you need to get serious about stashing away some money today to help cover your health costs in retirement. Even when you are covered by Medicare and any other health insurance, you still are going to have to pay for some costs, including premiums, deductibles, co-pays and - most importantly for many retirees - prescription drugs.