Your Test Results Rule Out Diabetes Insipidus
You do not have diabetes insipidus. Your water-fasting test demonstrates completely normal kidney concentrating ability (urine osmolality 498 mOsm/kg), normal ADH function (copeptin 4.6 pmol/L), and normal serum sodium (143 mEq/L)—all of which definitively exclude this diagnosis. 1
Why Diabetes Insipidus Is Ruled Out
Your test results show the opposite of what diabetes insipidus produces:
Your urine osmolality of 498 mOsm/kg is normal-to-concentrated. Diabetes insipidus requires urine osmolality <200 mOsm/kg in the presence of serum hyperosmolality—you are nowhere near this threshold. 1, 2
Your copeptin level of 4.6 pmol/L indicates normal ADH secretion. Nephrogenic diabetes insipidus requires copeptin >21.4 pmol/L, and your level is less than one-quarter of that diagnostic threshold. 1
Your serum sodium of 143 mEq/L is perfectly normal. Diabetes insipidus typically presents with high-normal or elevated sodium (>145 mEq/L when water access is restricted), especially during diagnostic testing. 1
Your ability to concentrate urine to 498 mOsm/kg after fasting proves your kidneys respond normally to ADH. Patients with diabetes insipidus cannot concentrate urine above 200 mOsm/kg even when severely dehydrated. 1
What Your Actual Urine Output Shows
Your reported output of 1,645 mL over 17 hours (~97 mL/hour) with 10 voids does not constitute true polyuria:
This volume extrapolates to approximately 2.3 L per 24 hours, which falls within or just above the normal adult range of 1.4–2.0 L/day. 3
True polyuria requires >3 L per 24 hours in adults. Your output is substantially below this threshold. 4, 2
Your average void volume is ~165 mL per void (1,645 mL ÷ 10 voids), which is entirely normal. Diabetes insipidus produces massive individual void volumes described as "bed flooding" in children and requiring extraordinary containment measures—your void volumes are unremarkable. 5
The Real Cause: Urinary Frequency, Not Polyuria
You have urinary frequency (voiding 10 times), not polyuria (excessive total volume). This is a critical distinction:
Likely Contributing Factors
Prolonged recumbency increases urinary frequency. You report lying down "day and night all the time." The supine position promotes venous return and increases renal perfusion, leading to more frequent (but normal-volume) voids without increasing total 24-hour output. 4
Overactive bladder (OAB) or reduced functional bladder capacity can cause frequent small-volume voids. Your 10 voids with normal total output suggests your bladder is signaling the need to void before reaching its full capacity. 4
Medication review is warranted. While none of your medications (losartan, pantoprazole, atorvastatin, apixaban, levothyroxine, clonazepam, escitalopram) directly cause diabetes insipidus, losartan can occasionally affect electrolyte balance, and SSRIs like escitalopram have been associated with urinary symptoms in some patients. 1
What to Do Next
Complete a 3-day frequency-volume chart documenting every void time and measured volume, plus total fluid intake. This will objectively show whether you have true polyuria (>3 L/day) or just frequent voiding of normal volumes. 4, 2
Assess for nocturnal polyuria specifically. If >33% of your 24-hour output occurs during your main sleep period, this suggests a different mechanism (such as mobilization of dependent edema when supine, despite your report of no visible swelling). 4, 2
Consider urinalysis and post-void residual measurement to exclude urinary tract infection, incomplete bladder emptying, or other bladder dysfunction. 4, 2
Evaluate for overactive bladder syndrome. Your pattern of frequent small voids without nocturia (you report not waking at night to urinate) is more consistent with daytime OAB than with any systemic cause of polyuria. 4
Common Pitfalls to Avoid
Do not pursue further diabetes insipidus testing. Your water-fasting test already provides definitive evidence against this diagnosis—additional water deprivation or desmopressin trials are unnecessary and potentially harmful. 1
Do not restrict fluid intake. Your thirst mechanism is functioning normally (as evidenced by normal sodium), and you should continue drinking according to thirst. 1
Do not assume all frequent urination is pathological. Given your prolonged recumbency and normal total output, your voiding pattern may simply reflect positional fluid shifts and a lower threshold for bladder fullness rather than disease. 4