You can deduct only the actual amount that you paid out of your pocket. The billed amount doesn't matter, what insurance paid doesn't matter, all that matters is what you actually paid out of your pocket.
For what it's worth, I've concluded that any health insurance co-share deductible (meaning what you have to pay out of pocket before the health insurance company starts paying anything) is accounted for in either of two ways, whichever is applicable: If you have an insurance plan that covers the Part B deductible, that deductible is included in the premium; If your insurance plan does NOT cover the Part B deductible, then that Part B deductible is covered by what you paid out of pocket.
An example of the latter is as follows: The (Medicare Part B) insurance deductible for 2022 is $233.00. Therefore, as you start the year off with doctor visits, prescriptions, etc, you are actually paying down that deductible out of pocket until you reach $233.00. Therefore, when you get your out-of-pocket total for the year, it includes the Part B deductible that you paid down.
So, the deductible is accounted for either in your plan premium or your total out-of-pocket. If anyone can explain this better or notices an error in this explanation, please feel free to comment. I hope this helps.