Is a fasting blood glucose of 93 mg/dL, a blood urea nitrogen of 6 mg/dL, and a calculated serum osmolality of 291 mOsm/kg within normal limits?

Your Laboratory Values Are Within Normal Limits

Your fasting glucose of 93 mg/dL, BUN of 6 mg/dL, and calculated serum osmolality of 291 mOsm/kg all fall within normal reference ranges for adults without diabetes.

Fasting Glucose Assessment

Your fasting glucose of 93 mg/dL is normal and reassuring:

• Normal fasting blood glucose is defined as less than 100 mg/dL (5.6 mmol/L) by current American Diabetes Association criteria 1, 2
• The optimal range for adults without diabetes is 70-99 mg/dL (3.9-5.5 mmol/L) 1
• Your value of 93 mg/dL places you comfortably in the middle of the normal range, well below the 100 mg/dL threshold where impaired fasting glucose (prediabetes) begins 3, 4
• Prediabetes is defined as fasting glucose of 100-125 mg/dL, and diabetes as fasting glucose ≥126 mg/dL on two separate occasions 3

Important context: Day-to-day biological variation in fasting glucose ranges from 4.8-6.1%, meaning your true fasting glucose could naturally fluctuate between approximately 87-99 mg/dL on different days without any metabolic change 1, 2

Blood Urea Nitrogen (BUN) Assessment

Your BUN of 6 mg/dL is at the lower end of normal but not concerning:

• Normal BUN typically ranges from 7-20 mg/dL in most laboratories, though reference ranges may vary slightly 5, 6
• A BUN of 6 mg/dL may reflect adequate hydration, lower protein intake, or normal kidney function with efficient urea clearance 5
• This value contributes minimally to your serum osmolality calculation and does not suggest any pathology 5, 7

Serum Osmolality Assessment

Your calculated serum osmolality of 291 mOsm/kg is normal:

• Normal serum osmolality ranges from 275-295 mOsm/kg 5, 8
• The most accurate formula for calculating serum osmolality is: Osmolality = 2[Na⁺] + (glucose in mg/dL)/18 + (BUN in mg/dL)/2.8 5, 7
• Your value of 291 mOsm/kg falls well within the normal range and indicates appropriate fluid balance and electrolyte homeostasis 5, 8
• Serum sodium concentration is the major determinant of serum osmolality under normal conditions 8

Clinical significance: Normal serum osmolality indicates that you do not have hyperosmolar or hypoosmolar states, which can cause neurologic symptoms ranging from mild confusion to life-threatening complications 8

Common Pitfalls to Avoid

• Do not interpret a single fasting glucose reading in isolation—biological variation means values can fluctuate 4.8-6.1% day-to-day without true metabolic change 1, 2
• Ensure proper fasting conditions—at least 8 hours of no caloric intake is required for accurate fasting glucose interpretation 3
• Do not use point-of-care glucose meters for diagnosis—laboratory venous plasma glucose measurements are required for diagnostic accuracy 3
• Confirm any abnormal results with repeat testing on a different day before making a diagnosis of prediabetes or diabetes 3, 1

Follow-Up Recommendations

• If you have risk factors for diabetes (BMI ≥25 kg/m², family history of diabetes, sedentary lifestyle, hypertension, dyslipidemia, or belonging to high-risk ethnic groups), consider screening every 3 years even with normal current values 3, 4
• Maintain a healthy lifestyle with regular physical activity and balanced diet to preserve normal glucose metabolism 3, 4
• No immediate follow-up testing is needed based on these normal values alone 1, 2