Difference between Glucometer and Lab test Glucose (Sugar) Readings

Diabetes Mellitus is a disorder of glucose homeostasis and monitored by measurement of:

  • Blood glucose levels.
  • Glycated hemoglobin (HbA1c) levels.

Blood glucose measurements are routinely done by:

  • Blood sample (venous sample) in the laboratory.
  • With the glucometer using capillary blood sample by finger prick.

difference between glucometer and lab test glucose readings


  • Venous blood glucose levels are the same as capillary blood glucose levels during fasting.
  • After meals, venous blood glucose levels are ≈ 10% lower than capillary blood glucose.
  • Whole blood glucose levels are 12 – 15% lower than plasma concentrations.
  • Some glucometers are calibrated to report whole blood glucose.
  • Most of the currently marketed glucometers give results as equivalent to venous plasma glucose.
  • Laboratory methods of blood glucose measurements are more accurate than glucometer values.
  • The majority of the glucometers conform to the International Organization for Standardization (ISO) standards that 95% of the readings <72 mg/dl are within 15% of the actual values and for higher glucose readings within 20% of the correct values.
  • For the regular monitoring of blood glucose, glucometers are handy tools.

If the glucose readings are not fitting with the usual pattern, then recheck the glucose readings in the laboratory.

  1. Take the glucometer to the laboratory
  2. Give the blood sample for the glucose measurement in the laboratory
  3. Immediately check the blood glucose with the glucometer using capillary blood after finger prick.
  4. If the glucometer glucose values are within 15-20% of the laboratory glucose values, then the glucometer values are accurate and can be used for regular monitoring of blood glucose.

Glucometers are useful for the self-monitoring of blood glucose (SMBG) for patients with Type 1 Diabetes, Type 2 Diabetes, GDM (Gestational diabetes mellitus).

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