No, These Values Do Not Indicate Diabetes Insipidus
Your serum osmolality of 295 mOsm/kg and serum sodium of 143 mmol/L are both within normal range and do not meet diagnostic criteria for diabetes insipidus. 1
Why These Values Are Normal
- Normal serum osmolality ranges from 275-295 mOsm/kg, and your value of 295 sits at the upper limit of normal but is not elevated 2
- Normal serum sodium ranges from approximately 135-145 mmol/L, and your value of 143 is well within this range 3
- Diabetes insipidus requires elevated plasma osmolality (>300 mOsm/kg H₂O) combined with inappropriately diluted urine (<200 mOsm/kg H₂O) 1
What Diabetes Insipidus Actually Looks Like
The diagnostic hallmark requires three simultaneous findings 4, 5:
- Elevated serum osmolality >300 mOsm/kg H₂O (you have 295, which is normal)
- High-normal or elevated serum sodium (typically >145 mmol/L, often much higher)
- Inappropriately diluted urine with osmolality <200 mOsm/kg H₂O despite the elevated serum values
The critical diagnostic feature is the dissociation between high plasma osmolality and low urine osmolality - the kidneys fail to concentrate urine despite dehydration 1. Your normal values show no such dissociation.
Clinical Context Matters
- Patients with diabetes insipidus typically present with severe polyuria (excessive urination) and polydipsia (excessive thirst), not just laboratory abnormalities 4, 6
- In documented cases, serum sodium often reaches extreme levels (e.g., 175 mmol/L) with serum osmolality around 337 mOsm/kg 7
- A normal serum osmolality does not rule out other conditions, but it effectively excludes diabetes insipidus as the primary diagnosis 5
Important Caveat
If you are experiencing polyuria and polydipsia despite these normal laboratory values, you should still undergo full diabetes insipidus evaluation 5. However, based solely on the laboratory values you've provided, diabetes insipidus is not present.