Why am I experiencing polyuria and intermittent hypokalemia despite normal serum sodium (143 mmol/L), normal serum osmolality (301 mOsm/kg), normal urine osmolality (498 mOsm/kg), normal copeptin (4.6 pmol/L), normal renal function and imaging, and no diuretic use, in the setting of anxiety and current medications (losartan, pantoprazole, atorvastatin, apixaban (Eliquis), levothyroxine (Synthroid), clonazepam, escitalopram (Lexapro))?

Your Test Results Rule Out Diabetes Insipidus

Your laboratory findings definitively exclude diabetes insipidus as the cause of your symptoms. Your urine osmolality of 498 mOsm/kg demonstrates excellent urinary concentrating ability, your copeptin level of 4.6 pmol/L confirms normal vasopressin function, and your serum sodium of 143 mmol/L with serum osmolality of 301 mOsm/kg are both normal. 1, 2

Why Diabetes Insipidus Is Ruled Out

Diabetes insipidus requires three pathognomonic features that you do not have:

• Inappropriately dilute urine (<200 mOsm/kg) combined with high-normal or elevated serum sodium—your urine osmolality of 498 mOsm/kg is more than double the diagnostic threshold and demonstrates normal kidney concentrating ability 1, 3
• Copeptin <21.4 pmol/L with inability to concentrate urine—your copeptin of 4.6 pmol/L is normal, but critically, you CAN concentrate your urine to 498 mOsm/kg, proving your vasopressin system works properly 1, 2
• Polyuria (>3 liters/24 hours in adults) with dilute urine—true diabetes insipidus produces massive urine volumes with osmolality typically around 100 mOsm/kg, not 498 mOsm/kg 1, 4

The ability to concentrate urine to 498 mOsm/kg after a 12-hour fast indicates normal ADH secretion and normal kidney response to ADH. 1 This single finding alone excludes both central and nephrogenic diabetes insipidus. 1

Most Likely Explanations for Your Symptoms

Anxiety-Related Polydipsia and Polyuria

Your anxiety disorder is the most probable cause of your urinary frequency. Patients with anxiety commonly develop increased fluid intake driven by psychological factors rather than true physiologic thirst, leading to secondary polyuria with appropriately dilute urine. 3 Unlike diabetes insipidus, these patients maintain normal serum sodium because their kidneys appropriately dilute the excess water intake. 3

• Your medications (clonazepam and escitalopram) confirm active anxiety management 5, 6
• Anxiety-driven polydipsia produces frequent urination with normal kidney function and normal concentrating ability—exactly matching your presentation 3
• The intact thirst mechanism in anxiety patients drives fluid intake beyond physiologic needs, but the kidneys respond normally by producing dilute urine to maintain electrolyte balance 3

Medication-Related Hypokalemia

Your intermittent hypokalemia is most likely caused by losartan, not a primary kidney disorder. While losartan typically causes hyperkalemia through renin-angiotensin-aldosterone system inhibition, paradoxical hypokalemia can occur through several mechanisms:

• Losartan can occasionally cause hypokalemia in some patients, particularly when combined with dietary factors or other medications 5
• Pantoprazole (proton pump inhibitor) can contribute to hypokalemia through magnesium depletion, which impairs potassium retention 5
• Your normal kidney function, normal calcium, and normal imaging exclude primary renal tubular disorders that would cause persistent hypokalemia 7

Monitor serum potassium, magnesium, and consider potassium supplementation if levels drop below 3.5 mmol/L. 7, 5 Discuss with your physician whether losartan dose adjustment or addition of a potassium-sparing agent is appropriate. 5, 8

What You Should Do Next

Immediate Actions

• Track your actual 24-hour urine volume to objectively quantify whether you truly have polyuria (>3 liters/day) or just increased urinary frequency with normal total volume 1, 4
• Monitor your fluid intake to determine if you are drinking excessively due to anxiety rather than true physiologic thirst 3
• Check serum glucose and HbA1c to definitively exclude diabetes mellitus as a cause of polyuria, as osmotic diuresis from hyperglycemia can mimic some symptoms 1

Follow-Up Testing

• Repeat serum potassium and add serum magnesium to evaluate the intermittent hypokalemia pattern 7, 5
• Consider 24-hour urine collection for sodium, potassium, and volume if polyuria is confirmed, to distinguish between water diuresis and osmotic diuresis 4

Management Approach

Address anxiety as the primary driver of symptoms:

• Optimize anxiety management with your psychiatrist, as improved anxiety control often reduces polydipsia and urinary frequency 3
• Avoid excessive fluid intake beyond thirst—drink to satisfy thirst rather than on a schedule 1
• Continue current medications unless your physician recommends changes based on potassium monitoring 5

Critical Pitfalls to Avoid

Do not restrict water access or attempt water deprivation testing. While you do not have diabetes insipidus, water restriction is unnecessary and potentially harmful in anxiety-related polydipsia. 1 Your normal serum sodium of 143 mmol/L indicates you are maintaining appropriate fluid balance. 1

Do not assume all polyuria requires aggressive intervention. If your 24-hour urine volume is actually normal (<3 liters/day), you simply have urinary frequency, not true polyuria, and the focus should remain on anxiety management. 4

Monitor for medication-induced electrolyte disturbances. Your combination of losartan and pantoprazole requires periodic potassium and magnesium monitoring, particularly if you develop muscle weakness, cramps, or palpitations. 5, 8