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Diabetes Screenings: Diurnal Glucose Variation Creates Doubt About Afternoon Sessions


Patients’ plasma glucose concentrations are highest in the morning and decline consistently before reaching a plateau at about noon. Because of this “dawn phenomenon,” the criteria for diagnosing diabetes may need to be adjusted for the time of day the blood sample was obtained, especially when fasting glucose values are determined from afternoon samples.


Troisi RJ et al. Diurnal variation in fasting plasma glucose: implications for diagnosis of diabetes in patients examined in the afternoon. JAMA. 2000;284:3157–9.