Why is my urine output abnormal at night?

Q: I drink one and a half litres of water in a day. During the day, urine flow is normal, but at night I pass around 500 ml of urine, which disturbs my sleep. Is it normal or I have to see a urologist?

A:You seem to have more output during night than during day. A pysicians first duty would be to confirm the same with a voiding diary which lists urine output and fluid intakes over a period of 24 hours. Most common cause for such discrepant pattern is more fluid intake in the evenings. Other medical causes which need investigations include diabetes, and failure of kidneys normal concentrating ability at night. The latter may happen with some renal interstitial diseases and absence of normal circadian rhythmicity of the concentrating hormone called anti diureteic hormone. These may be investigated by your physician by checking blood sugar and early morning urinary osmolality & pH after overnight dehydration.