One thing that can happen--although it usually happens to old people...

If your intake of calcium and other minerals is chronically/very low, your body takes calcium out of your bones (after using up your soft tissue mineral reserve) to buffer the pH of your blood. It's called emergency alkalosis. The main problem with that is it's a very imprecise mechanism--it doesn't just take what it needs it takes more than it needs, but it's not good at putting it back where it got it from. So when it's done accomplishing its tasks it sticks the calcium in random places, and that's how you get bone spurs/calcium deposits and even eye floaters.

But even if that were going on, I don't know that your urine pH would go as high 8. Your body would have to be borrowing way more than it needs. And given your age, you'd have to have an infection or a couple of leaking dental fillings for your body to be in this mode in the first place. Also, IMO, 2 hrs is too soon after consuming something to gauge its impact on your pH. The bladder accumulates urine over time--I think of my urine pH as the *average* of what's happened in the body over the last 2.5-4.5 hours, although I often change my mind on the numbers and I admit I haven't researched it.

How's your calcium intake? Any toothaches?

drugs, such as benzos can affect pH values and cause your buffering system to whack out - leading to over corrections\extremes.

As you plan on doing, wean off of the benzos, first, deal with your dietary\nutritional needs second, and then worry about pH.

grz-