Medical reasons for nocturia (waking to pee at night) include:
A high blood sugar level cause sugar to spill into urine, dragging lots of water with it.
A high blood calcium level. Calcium from the blood can get into urine, pulling water along with it
Kidney disease. Some kidney conditions cause the kidneys to make excessive amounts of urine.
Too little antidiuretic hormone. Without this hormone, the body can’t hold on to water. This condition is called diabetes insipidus.
Urinary tract infection. Bacteria in the urine can inflame the bladder, causing frequent urination.
Diuretics (“water pills”) and some other medications cause the body to make extra urine.
Sleep apnea and restless legs syndrome. Both of these sleep-related disorders awaken people from sleep. Such awakenings may prompt them to make a trip to the bathroom.
Water retention in the legs (edema). Fluid that accumulates in the legs during the daytime may move to the kidneys, and then out into urine, at night.
Usually occurs in adults, however consider in children