| Mechanism | Condition | Diagnostic criteria |
| Small-volume bladder voids | Urgency, sometimes with urge incontinence, urinary frequency (>8 voids/24 hours), and/or nocturia | Daytime voids ≥8, urgency, nocturia, and urge incontinence |
| BPH or BOO | BPH: AUA-7 SI >8 and peak uroflow between 4 and 15 mL/sec; BOO: evidence of obstruction, including peak uroflow less than 15 mL/sec | |
| Urinary tract infection | Leukocyte esterase on U/A; presence of white blood cells >5 HPF on microscopic examination; >1000 colony-forming units by culture | |
| Low bladder capacity | Cystometric capacity less than 150 mL | |
| Increased urine output at night | Nocturnal polyuria | 35 percent or more of 24-hour urine output occurring during sleep hours, may be related to loss of diurnal variation or deficiency for arginine vasopressin |
| Peripheral edema (without heart failure) | Presence of pitting edema 10 cm above ankle | |
| Congestive HF | Echocardiographic evidence of a LVEF <35 percent; presence of S3; bilateral lung crackles; use of an ACE inhibitor for HF | |
| Poor control of diabetes mellitus | Random glucose >200 mg/dL (11.1 mmol/L); glucosuria on urine dipstick | |
| Excessive fluid intake throughout day or large fluid intake immediately prior to bedtime | Analysis of self-reported intake or recorded voiding diary or fluid intake record | |
| Intake of diuretic substances | Analysis of self-reported intake | |
| Sleep-related disorders | Difficulty with sleep maintenance | Self-reported sleep latency of >30 minutes following first awakening for nocturia |
| Sleep apnea | Daytime sleepiness, loud snoring, witnessed breathing interruptions, or awakenings due to gasping or choking in the presence of at least 5 obstructive respiratory events per hour of sleep* | |
| Restless leg syndrome or periodic limb movements | History, partner report, or nighttime sleep study | |
| Unknown mechanism | Hypertension | >140/90 mmHg supine |
