What causes low serum phosphate other than parathyroidism? PTH & calcium are constantly normal. Normal D vitamin because of high dose supplements.

Low phos. Phos metabolism is intake /shift/ losses. I am assuming you have good intake. So the other two are the reason, either shift inside the cells or losses from the kidney. How low is the phos? Your medication list shows no meds that can cause losses. A lab doesn't need to be treated, so rpt lab and then get a urine fractional excretion if still low. Talk to your MD. .