I've made accommodations with my employer that I can take additional sick days as needed for days where I'm bed-ridden sick and have no energy for even self-care. On other days, I'm super-productive and a top notch employee.
One of the annoyances I encounter is that whenever I renew my accommodations with HR, they always need to know "how many" days off I will be requesting for the upcoming next 3 months, as if I knew the exact number of days I'd be medically incapacitated. I am always left putting a number that represents the stats from the last 3 months, even though the stats of the next 3 months could be much higher or lower, of course.
How have other people managed accommodations for days off with work?