Blood Glucose, A1c, Cholesterol and Hematology Tests

Blood Glucose and Hemoglobin A1c Testing

Capillary blood glucose testing measures the concentration of glucose in peripheral blood using a point-of-care glucometer. In the outpatient medical office, point-of-care blood glucose testing is typically classified as a CLIA-waived test. To perform a capillary puncture on an adult, routinely select the lateral or medial side of the third or fourth fingertip. Before puncturing, cleanse the site with an alcohol wipe and allow the skin to air-dry completely. Allowing the alcohol to dry prevents stinging for the patient and prevents hemolyzing the blood specimen. When collecting the blood drop, follow the glucometer manufacturer's instructions and clinic protocol regarding whether to wipe away the first drop of blood, as residual alcohol or interstitial tissue fluid can alter test results. Avoid excessive squeezing or milking of the fingertip, which can hemolyze the sample and contaminate it with tissue fluids.

Quality control ensures that glucometers provide accurate clinical data. Medical assistants must perform glucometer quality control at the intervals specified by the manufacturer and clinic protocol, which includes running controls whenever a new vial of test strips is opened if required. Always store point-of-care test strips in their original packaging as directed by the manufacturer, keep strip containers tightly closed when applicable, and check expiration dates prior to use. For a non-diabetic adult, a normal fasting blood glucose reference range is generally 70 to 99 mg/dL. A blood glucose level below 70 mg/dL is generally considered hypoglycemia, requiring the medical assistant to promptly notify the provider and follow clinic protocol. A fasting laboratory plasma glucose level of 126 mg/dL or higher meets a diagnostic criterion for diabetes when confirmed as required, though the provider makes the formal diagnosis. The medical assistant must immediately report any critically low or high blood glucose values to the supervising provider.

While a glucometer shows a patient's immediate blood sugar level, the Hemoglobin A1c test measures the percentage of hemoglobin bound to glucose over the preceding two to three months. This provides an index of long-term glycemic control because the average lifespan of an erythrocyte is approximately 120 days. Unlike routine fasting blood glucose, Hemoglobin A1c testing does not require the patient to be in a fasting state prior to collection. A normal Hemoglobin A1c value for a non-diabetic adult is typically less than 5.7 percent, whereas a result between 5.7 percent and 6.4 percent indicates prediabetes. A laboratory Hemoglobin A1c result of 6.5 percent or higher meets a criterion for diabetes when confirmed as required, with the final diagnosis determined solely by the provider. CLIA-waived point-of-care A1c analyzers commonly utilize capillary whole blood obtained via fingerstick, while venipuncture collection for laboratory testing requires a lavender-top tube containing the anticoagulant EDTA.