Do I have diabetes insipidus given my normal serum sodium levels, variable urine output and osmolality, and absence of chronic kidney disease or diabetes mellitus?

You Do Not Have Diabetes Insipidus

Based on your clinical presentation, laboratory values, and symptom pattern, you do not meet diagnostic criteria for diabetes insipidus. Your normal serum sodium (143 mmol/L), relatively modest urine output (2-2.5 L/24h), and variable urine concentration patterns are inconsistent with this diagnosis.

Why Diabetes Insipidus Is Ruled Out

Diagnostic Criteria Not Met

• Diabetes insipidus requires polyuria exceeding 3 liters per 24 hours in adults, and your reported output of 2-2.5 L/24h falls well below this threshold 1, 2, 3
• The pathognomonic triad for DI is: polyuria, polydipsia, and inappropriately dilute urine (osmolality <200 mOsm/kg H₂O) combined with high-normal or elevated serum sodium 4
• Your urine osmolality of 170 mOsm/kg H₂O on that single day, while low, occurred in the context of normal serum sodium (143 mmol/L) and serum osmolality (300 mOsm/kg), which does not support DI 4

Your Void Volumes Are Normal

• Patients with true DI produce massive individual void volumes described as "bed flooding" in children, requiring double diapers, with continence not achieved until 8-11 years of age due to overwhelming per-void volumes 5
• Your reported void volumes of 200-300 mL are completely normal for adults and nowhere near the extraordinary volumes seen in DI 5
• DI patients demonstrate approximately 46% incidence of urological complications including incomplete bladder voiding and urinary tract dilatation from chronic massive volumes 5, which you do not have

Your Serum Osmolality Pattern Is Reassuring

• Serum osmolality >300 mOsm/kg is classified as dehydrated in the context of low fluid intake, but this is a normal physiological response, not pathological 6
• Your serum osmolality of 300 mOsm/kg on the day you were "peeing a lot" with clear urine suggests you were simply well-hydrated or over-hydrated (possibly from the multivitamin effect you described), and your body was appropriately diluting urine 6
• In true DI with hypernatremic dehydration, serum osmolality typically exceeds 300 mOsm/kg H₂O while urine remains inappropriately diluted at <200 mOsm/kg H₂O 7, but your serum sodium remained normal

What Actually Explains Your Symptoms

Transient Physiological Response

• Your description of taking a multivitamin for 3 days followed by increased urination with colorless urine, then return to normal (dark yellow urine in morning, light yellow later) after stopping the vitamin, represents normal physiological variation in hydration status 6
• Urine concentration varies normally based on hydration status, and morning urine is typically more concentrated (darker) after overnight fasting from fluids 6

Anxiety-Related Factors

• Your clinical anxiety and sedentary lifestyle in bed may contribute to heightened awareness of normal bodily functions, including urination patterns
• The fact that you don't wake at night to urinate or drink is highly inconsistent with DI, where nocturnal polyuria with night waking is a hallmark feature 1

The Creatinine Fluctuation Was Spurious

• Your creatinine elevation to 1.27 (eGFR 48) followed by normalization to 0.9 (eGFR 78) the next day was likely due to recent red meat consumption 2-3 hours before labs, which transiently elevates creatinine without representing true kidney dysfunction 6
• This rapid normalization confirms no underlying chronic kidney disease 6

Key Distinguishing Features You Lack

Patients with true diabetes insipidus present with:

• Polyuria >3 L/24h (you have 2-2.5 L) 1, 2
• Persistent dilute urine even during water deprivation (your urine varies from clear to dark yellow) 1
• Nocturnal polyuria requiring multiple nighttime voids (you don't wake at night) 1
• Massive per-void volumes causing bladder dysfunction (your 200-300 mL voids are normal) 5
• Inability to concentrate urine with osmolality persistently <200 mOsm/kg (your single measurement doesn't establish a pattern) 4, 1

Clinical Pitfall to Avoid

A single set of laboratory values showing low urine osmolality in the context of high fluid intake or vitamin supplementation does not diagnose DI. The diagnosis requires demonstration of persistent inability to concentrate urine despite physiological stimuli (dehydration, elevated serum osmolality) 1, 8. Your ability to produce dark concentrated urine when not over-hydrated proves your kidneys can concentrate urine normally.

What You Should Do

• Reassurance is appropriate - your symptoms represent normal physiological variation
• Continue your anxiety management, as health anxiety may be amplifying awareness of normal bodily functions
• No further workup for diabetes insipidus is warranted given your clinical presentation 4
• If polyuria truly exceeds 3 L/24h persistently with inability to concentrate urine, then formal evaluation with simultaneous serum and urine osmolality measurements would be indicated 4, 1