Elevated Alk Phosphate

First of Aug was in hospital with viral gastroenteritis, potassium dropped to 2.7 so had to stay couple days to build that up some with IVs.  A month later still was having nausea daily, but I have gastroparesis pretty bad so didn't get too alarmed.  But...as the story goes, I get so tired, also blamed on working 9 or 10 hr days at office, but with the fatigue, nausea causing loss of appetite, the doc ordered lab test.  My alk phos was 166 with the high normal value to be 135.  My internal medicine dr called yesterday wanting a fasting BS, gave me K+ and in one week repeat those plus another alk phos test.  Wonder what the relationship between the BS and alk phosphate?  Or him thinking BS for weakness/fatigue then just wanting to repeat the alk phos?
I have been having to take every 8 hrs Tylenol Arthritis for constant deep aching from neck to waist in my whole back and into my shoulder.  All the muscles in my back seem to hurt if twist my body.