My health insurance will pay for blood work. No deductible.
Look, your own words here:
"He said he wants to do blood work, because he thinks it's almost impossible for me to have a 800 level at age 48."
It's NOT impossible at all - we're all different, I've talked to guys who've never cycled with the blood work to show natty test at 1,600. And they weren't in their 20s. You might be blessed with genes that give you 800 at your age - in which case us other old guys hate you (a little).
What is quite possible is the doc getting afraid of losing a paying customer.
Plan A - do nothing, enjoy your 800 and come back in 10 years or when it drops below 400
Plan B - corollary to A above, do more homework, work your ass off in the gym, eat and sleep right, and after 2 years or so, if you feel compelled, start cycling
Plan C - manipulate your natty levels to create misleading blood work that'll let doc prescribe test (and it has to be injectable, done by you, at home) - e.g. don't sleep for 24 hours or so, drink loads of coffee and full sugar Coke before getting bloods done - but since you're at 800, might need to be more extreme, take steroids to shut yourself down, many ways to skin that cat, some depend on how sophisticated your doc is (not much from what I see)
Do annual blood panels in all scenarios.
That's how I'd think about it.