Dr. Tareq Abadl: Why Does MCV Falsely Increase When Blood Glucose Is High?
Dr. Tareq Abadl, Medical Laboratory Specialist and Director of the Blood Bank at Dr. Abdelkader Al-Mutawakkil Hospital, shared a post on LinkedIn:
“Why Does MCV Falsely Increase When Blood Glucose Is High?
When reviewing a CBC report, a high MCV (Mean Corpuscular Volume) usually makes us think of vitamin deficiencies like B12 or folate.
But hold on! If the patient has severe hyperglycemia, the MCV can appear elevated — and it’s not real. It’s simply a false increase caused by high glucose levels.
What’s the mechanism?
1. High Glucose in Plasma
When blood glucose is significantly elevated, its concentration outside the red blood cells becomes much higher than inside.
2. Osmosis Effect
Red blood cells try to balance this difference by pulling water into the cell through osmosis.
3. Temporary Cell Swelling
As water enters, the RBCs swell and become larger than normal.
4. Analyzer Interpretation
The hematology analyzer detects these swollen cells and reports a higher MCV, even though the true cell size hasn’t changed.
Key Point
This increase is falsely elevated, not a sign of a real RBC abnormality.
Once blood glucose levels normalize, the cells return to their normal size, and the MCV value drops back to baseline.”
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