Impact of Hematocrit on Blood Glucose Measurements

Mechanism of Interference

A mild drop in hemoglobin and hematocrit can significantly affect blood glucose measurements, typically causing falsely elevated readings on point-of-care glucose meters, particularly when hematocrit falls below 35% 1, 2
Low hematocrit directly interferes with glucose meter accuracy through hemodilution effects, altering the electrochemical properties of whole blood samples and leading to systematic measurement errors that vary by meter technology 1, 2
Glucose oxidase-based meters produce falsely high glucose readings at low hematocrit (<35%) 1, 2
Glucose dehydrogenase-based meters show variable effects depending on the specific coenzyme system used 1, 2

A patient with true glucose of 80 mg/dL and hematocrit of 0.25 may show a positive bias of up to 18 mg/dL on point-of-care meters, leading to inappropriate insulin dosing decisions and undetected hypoglycemia 3

Anemia (any etiology causing hematocrit <35%) can interfere with glucose measurements 1, 2
Chronic kidney disease with associated anemia can also affect glucose readings 1, 2
Acute blood loss or recent hemorrhage can cause hemodilution, leading to low hematocrit 4
Hemodilution from fluid resuscitation or volume expansion can also affect glucose measurements 5
Medication effects, such as thiazolidinediones, can cause plasma volume expansion with hemoglobin drops and hematocrit decreases 5

Point-of-care glucose meters can produce falsely high glucose readings at low hematocrit, while HbA1c measurements can be falsely low in conditions that shorten red blood cell lifespan, including some anemias 1, 2, 4, 6

Verify the glucose meter technology and avoid glucose oxidase-based meters in patients with hematocrit <35% 1, 2
Use alternative sampling methods, such as sending venous or arterial samples to the central laboratory using hexokinase-based methods, which are not affected by hematocrit 1, 3
Consider continuous glucose monitoring (CGM) to bypass hematocrit interference entirely 1, 2
Interpret discordant results cautiously and suspect hematocrit interference when glucose meter readings seem inconsistent with clinical presentation or HbA1c 4, 6

Avoid glucose oxidase-based (GO) meters and GDH-PQQ meters in patients with hematocrit <35% 1, 2
Prefer hexokinase-based (HK), GDH-NAD, or GDH-FAD methods that show less hematocrit sensitivity 1, 2
Use only professional-grade meters meeting FDA 2020 standards (95% within 12% of laboratory results) in hospital settings 7