Your Test Results Are Normal and Reassuring
Your serum osmolality of 295 mOsm/kg and urine osmolality of 220 mOsm/kg indicate normal hydration status with appropriate kidney function—eating cookies before the test did not meaningfully affect the interpretation. 1, 2, 3
Understanding Your Results
Serum Osmolality (295 mOsm/kg)
- Your serum osmolality falls within the normal reference range of 275-305 mOsm/kg and is below the 300 mOsm/kg threshold that would indicate dehydration. 1, 2, 3
- The Clinical Nutrition society defines serum osmolality >300 mOsm/kg as the rigorous cut-off for low-intake dehydration, which you do not meet. 1, 2
- Even using the more sensitive calculated osmolarity screening threshold of >295 mmol/L (which triggers further evaluation), your value of 295 is at the borderline and does not indicate pathology. 1, 3
Urine Osmolality (220 mOsm/kg)
- Your urine osmolality of 220 mOsm/kg indicates appropriately dilute urine, which is normal when serum osmolality is in the normal range. 2
- This demonstrates that your kidneys are functioning properly—they are not over-concentrating urine because your body does not need to conserve water. 2
- The relationship between your normal serum osmolality and relatively dilute urine confirms adequate hydration with intact renal concentrating ability. 2, 4
Impact of Eating Cookies Before Testing
Glucose Effect on Osmolality
- Serum osmolality is the sum of sodium, chloride, bicarbonate, potassium, glucose, and urea concentrations. 1, 3, 4
- Eating cookies would temporarily raise your blood glucose, which could slightly increase serum osmolality by a few mOsm/kg. 3, 4
- However, interpretation of serum osmolality requires checking that glucose is within normal range—if your glucose was elevated from the cookies, this would be factored into the clinical interpretation. 1, 3
Why This Doesn't Change Your Results
- Your serum osmolality of 295 mOsm/kg remains well below the 300 mOsm/kg dehydration threshold even if cookies caused a small glucose-related increase. 1, 2
- In low-intake dehydration, it is common that despite raised serum osmolality, none of the major components (sodium, potassium, urea, or glucose) are raised out of normal range—instead, general fluid concentration leads to small rises within the normal range in all components. 1
- Your results do not show this pattern of generalized concentration. 1
What These Results Rule Out
Diabetes Insipidus
- Diabetes insipidus would present with serum osmolality >300 mOsm/kg alongside inappropriately dilute urine (osmolality <300 mOsm/kg), representing a medical emergency. 2
- Your normal serum osmolality excludes this diagnosis. 2, 5
Dehydration
- Dehydration is defined by serum osmolality >300 mOsm/kg and is associated with increased mortality risk and doubled risk of 4-year disability. 1, 2, 3
- Your value of 295 mOsm/kg does not meet this threshold. 1, 2
Overhydration
- Overhydration would present with serum osmolality <275 mOsm/kg. 3, 6
- Your value of 295 mOsm/kg is well above this threshold. 3
Clinical Bottom Line
- Your results demonstrate normal fluid balance with appropriate kidney concentrating function. 2, 3
- No intervention or follow-up testing is needed based on these osmolality values alone. 1, 2
- The cookies you ate before testing may have caused a minor, clinically insignificant elevation in glucose that slightly increased serum osmolality, but this does not change the interpretation that your hydration status is normal. 1, 3, 4