Do You Have Diabetes Insipidus?
Based on your laboratory values and clinical presentation, you do NOT meet diagnostic criteria for diabetes insipidus. Your urine osmolality of 220 mOsm/kg is inappropriately dilute but not low enough, your serum sodium is normal (not high-normal or elevated), and most importantly, a urine output of 3L/24 hours falls below the diagnostic threshold for DI 1.
Why This Is Not Diabetes Insipidus
Diagnostic Thresholds Not Met
Urine volume requirement: The Endocrine Society establishes that diagnosis of DI requires polyuria >3 liters per 24 hours in adults, and you are projecting exactly 3L, which is at the threshold but not definitively above it 1.
Urine osmolality is borderline: While your urine osmolality of 220 mOsm/kg is dilute, the diagnostic criteria for DI require urine osmolality definitively <200 mOsm/kg in the setting of serum hyperosmolality 1. Your value of 220 falls in an indeterminate zone where many conditions can cause similar findings without representing true DI 1.
Serum sodium is normal, not elevated: The pathognomonic triad for DI includes polyuria, polydipsia, and inappropriately dilute urine combined with high-normal or elevated serum sodium 1. Your serum sodium of 143 mEq/L is mid-normal range, not high-normal (typically ≥145 mEq/L) 1.
Serum osmolality is normal: Your serum osmolality of 295 mOsm/kg is within the normal reference range (275-305), whereas DI typically presents with serum hyperosmolality driving the inappropriate urinary dilution 1, 2.
ADH Level Interpretation
Your detectable ADH level of 0.8 pg/mL (reference range 0.0-4.7) is within normal limits and argues against central DI, which would show undetectable or very low ADH in the presence of elevated serum osmolality 1, 2.
If you had nephrogenic DI, you would have elevated ADH levels (as the body tries to compensate for renal resistance) along with persistently dilute urine despite the high ADH 2.
What Could Explain Your Findings
Alternative Diagnoses to Consider
Primary polydipsia: Excessive water intake can cause dilute urine with normal serum sodium because you're drinking enough to keep up with losses 2. This is the most likely explanation if you've been consuming large volumes of fluids voluntarily.
Partial dehydration or early renal dysfunction: Many conditions cause urine osmolality in the 200-300 mOsm/kg range without representing true DI, including chronic kidney disease or various renal disorders 1.
High dietary sodium or protein intake: These increase obligatory water excretion and can transiently elevate urine output 1.
Critical Pitfall to Avoid
Do not restrict your water intake to "test" whether you have DI—this is dangerous and can lead to severe hypernatremic dehydration if you actually do have an undiagnosed concentrating defect 1, 3.
Drinking Pedialyte or electrolyte solutions during self-testing invalidates results because these contain approximately 1,035 mg sodium per liter, representing a substantial electrolyte load that artificially increases urine output 1.
What You Should Do Next
If Symptoms Persist
Complete an accurate 24-hour urine collection under normal conditions (usual fluid intake based on thirst, no electrolyte solutions, no acute illness) to document true baseline urine volume 1.
See your physician for formal evaluation if you consistently produce >3L urine per 24 hours with persistent thirst, as this warrants simultaneous measurement of serum sodium, serum osmolality, and urine osmolality 1, 2.
Water deprivation test followed by desmopressin administration remains the gold standard for diagnosis if clinical suspicion persists, though newer copeptin measurement may simplify diagnosis 4, 2.