As millennials begin to turn 40 in 2021, CNBC Make It has launched Middle-Aged Millennials, a series exploring how the oldest members of this generation have grown into adulthood amid the backdrop of the Great Recession and the Covid-19 pandemic, student loans, stagnant wages and rising costs of living.

Every morning, Kristin Bennett starts her day off by swallowing about 14 different supplements and vitamins designed to help her keep the worst symptoms of her disease at bay. 

Bennett has relapsing-remitting multiple sclerosis, a central nervous system disease she's been dealing with for about 20 years after being diagnosed in 2001. She just turned 40 last month.

Health conditions like Bennett's can take a toll, both financially and emotionally. And unfortunately, as the oldest millennials start to hit 40, many are finding themselves coping with chronic health conditions — more so than previous generations, according to some recent research.