Why is the urine of patients with diabetes mellitus bright (almost neon) yellow? also, what causes the ph spike with diabetes insipidus?

Dehydration, fillers: Bright urine most often comes from dehydration (too little fluid or excess loss of fluids), often seen in diabetes. It can also come from the fillers and buffers in pills, including vitamins. pH spiking is alkalosis or excessively alkaline state from abnormal fluid and electrolyte dynamics. See your PCP or Endocrinologist for electrolyte lab work, and more info and discussion.