I did ask. "what if the blood test result is erroneous?" I had found it hard to believe that I could feel so well with such a potentially dangerous magnesium level. It turns out that a second test showed the level to be normal after all. So the hourly observations for blood pressure, temperature and blood oxygen level along with the drip were stopped at 2am and thereafter I slept very well until 6am by which time activities on the ward were well underway.
I have checked out of my room and am now in the chemo day room starting on the first drip which is the hydration. With good luck and no hold-ups I should be back home late afternoon.