Don’t feel bad, there’s lots to absorb and retain when it comes to the golden years!
I didn’t know but learned that if you enjoy a substantial capital gain, your SS check will be cut. I don’t know for how long yet. Had a $100k cap gain in 2016 and my check got cut by about 13%. Had a larger one in 17 so I may end up with very little SS income at this rate. About 7% of it goes to Medicare. An of course they tax your SS income if you make more than a pittance in other earned income.
Actually, SS benefits are not affected by capital gains BUT medicare premiums definitely are! SS benefits are only affected by "earned income" when under full retirement age, Medicare premiums are affected by "income". When you have taxable income exceeding $170,000 in a year, your medicare premium goes up, it can rise substantially the higher your income is. However, if it is a "one time event", you can file forms to have it reduced it subsequent years.