Do I have diabetes insipidus given my symptoms of polyuria (excessive urine production), low urine osmolality, and normal serum osmolality, which improved after stopping multivitamins?

You Do Not Have Diabetes Insipidus

Based on your clinical presentation, laboratory values, and symptom resolution, you do not meet diagnostic criteria for diabetes insipidus. Your urine output of 2-2.5 liters per 24 hours is below the diagnostic threshold, your symptoms were transient and resolved after stopping the multivitamin, and your urine osmolality of 170 mOsm/kg, while low, occurred in the context of appropriate physiologic dilution from increased fluid intake 1, 2.

Why This Is Not Diabetes Insipidus

Urine volume does not meet diagnostic criteria:

• True diabetes insipidus requires polyuria exceeding 3 liters per 24 hours in adults, with some patients producing volumes so massive they cause "bed flooding" at night 1, 3, 2
• Your reported output of 2-2.5 liters per 24 hours falls within normal to mildly elevated range 1
• You do not wake at night to urinate or drink, which is a hallmark feature of organic diabetes insipidus 2

Your osmolality pattern does not indicate diabetes insipidus:

• The pathognomonic triad for diabetes insipidus requires: (1) urine osmolality <200 mOsm/kg H₂O, (2) high-normal or elevated serum sodium, and (3) persistent polyuria despite attempts to reduce fluid intake 1
• Your serum sodium was normal at 143 mmol/L (not elevated), and your serum osmolality of 300 mOsm/kg is normal 1
• While your urine osmolality of 170 mOsm/kg was low, this occurred transiently during a period of increased fluid intake (likely from the multivitamin causing increased thirst), which is an appropriate physiologic response 1
• In true diabetes insipidus, urine osmolality remains maximally dilute (<200 mOsm/kg) even during dehydration and water restriction 1, 2

Symptom resolution excludes diabetes insipidus:

• Your symptoms resolved after discontinuing the multivitamin, indicating a transient cause rather than a permanent defect in vasopressin production or action 1
• Diabetes insipidus is a chronic condition requiring ongoing management; it does not spontaneously resolve 1, 4
• Your return to darker yellow urine indicates your kidneys are now appropriately concentrating urine, which would not occur in diabetes insipidus 1

What Actually Happened

Transient polyuria from multivitamin-induced increased fluid intake:

• Certain B vitamins (particularly B2/riboflavin) can cause bright yellow urine and may increase thirst perception, leading to increased fluid intake 1
• When you drink more water, your kidneys appropriately produce more dilute urine to maintain osmotic balance—this is normal physiology, not diabetes insipidus 1
• Your void volumes of 200-300 mL are normal; diabetes insipidus patients produce individual void volumes so massive they require "double nappies" in children and cause bladder dysfunction in 46% of adult patients 5, 3

Acute kidney injury from red meat consumption:

• Your initial creatinine of 1.27 with eGFR of 48 was likely due to red meat consumption 2-3 hours before testing, which transiently elevates creatinine through dietary creatine metabolism 6
• The rapid normalization to creatinine 0.9 and eGFR 78 the next day confirms this was not true kidney disease 6

Critical Reassurance Points

You do not need diabetes insipidus workup because:

• Your 24-hour urine volume is below the 3-liter diagnostic threshold 1, 2
• You have no nocturia (waking to urinate at night), which is nearly universal in diabetes insipidus 2
• Your symptoms resolved spontaneously, whereas diabetes insipidus is permanent without treatment 1, 4
• Your serum sodium remained normal throughout, whereas untreated diabetes insipidus causes progressive hypernatremia (sodium >145 mmol/L) and life-threatening dehydration 1

Your anxiety may be amplifying symptom perception:

• Clinical anxiety can heighten awareness of normal bodily functions, making you more conscious of urination frequency 1
• Your sedentary lifestyle and anxiety medication are not causes of diabetes insipidus 6
• The fact that you're monitoring void volumes and urine color this closely suggests health anxiety rather than objective pathology 1

What You Should Do

No further diabetes insipidus evaluation is needed, but consider:

• Avoid restarting the multivitamin that triggered your symptoms 1
• If you resume multivitamins, choose one without high-dose B vitamins or take with adequate food 1
• Continue your anxiety management, as health anxiety may be contributing to symptom hypervigilance 1
• Avoid red meat consumption within 24 hours of any future kidney function testing to prevent falsely elevated creatinine 6

Seek medical attention only if you develop:

• True polyuria exceeding 3 liters per 24 hours that persists despite reducing fluid intake 1, 2
• Nocturia requiring multiple awakenings to urinate 2
• Persistent thirst that cannot be satisfied 1
• Serum sodium >145 mmol/L with signs of dehydration 1