It can be due to many reasons which can be physiological or disease-related, and include excessive intake of liquids, diuretic substances (including tea, caffeine, alcohol, certain drugs), anxiety, exposure to cold,
diabetes mellitus,
diabetes insipidus (
central or
nephrogenic), urinary tract infections or obstruction, etc to name a few more common ones.
In your case, urinary tract infection should be ruled out by getting a complete urine examination and a urine culture done.
I hope it helps.