Rule of Thomas for Hemoglobin A1c Conversion

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• published: 17 Jul 2015
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The Rule of Thomas for Hemoglobin A1c Conversion I love medical eponyms! Is it a delusion of grandeur to think that I could have a medical eponym of my own? Perhaps, but I will try regardless - please take my self-aggrandizement cum grano salis. Without further ado, I present: "The Rule of Thomas" for quickly calculating average blood glucose levels from Hemoglobin A1C percentages. Use the following formula: Average Blood Glucose = 120 mg/dL + 30 (HgbA1C% - 6%) Plug in your variable, namely the Hemoglobin A1C Percentage, and solve the equation. You will be left with an average blood glucose. For example, your 30 year old patient with type 1 diabetes typically has excellent control of their blood sugar. Because your patient is young and healthy, you encourage them to maintain tight glucose control. You order a blood draw and obtain a hemoglobin A1C level of 6.5%. You would then have to use a table to find what their average blood glucose would be, but if you use the Rule of Thomas, you will be able to calculate the average blood glucose quickly. Average Blood Glucose = 120 mg/dL + 30 (6.5% - 6%) Average Blood Glucose = 120 mg/dL + 30 (0.5%) Average Blood Glucose = 120 mg/dL + 15 mg/dL Average Blood Glucose = 135 mg/dL As another example, you have a 58 year old male with type 2 diabetes that is newly diagnosed and poorly controlled. His hemoglobin A1C level prior to treatment is 12%. Using the formula: Average Blood Glucose = 120 mg/dL + 30 (12% - 6%) Average Blood Glucose = 120 mg/dL + 30 (6%) Average Blood Glucose = 120 mg/dL + 180 mg/dL Average Blood Glucose = 300 mg/dL As the medical community moves to patient-centered approaches to managing chronic illness, The Rule of Thomas is an easy way for clinicians and patients to understand and work with Hemoglobin A1c levels and their correlating average blood glucose levels. The Rule of Thomas will help patients and clinicians communicate more easily about hemoglobin A1c and glucose levels. #bloodsugar #diabetes #diabetesmellitus #type2diabetes #bloodglucose #hemoglobinA1c #medicine #clinic #hospital #medicaleponyms #RuleofThomas #endocrine #endocrinology #medicaleducation #patientcentered #patientcommunication Key Links: Translating the A1C Assay Into Estimated Average Glucose Values: http://care.diabetesjournals.org/content/31/8/1473.abstract ADA Hemoglobin A1c to Average Glucose Level: http://professional.diabetes.org/glucosecalculator.aspx Mayo Clinic Hemoglobin A1c conversion chart: http://www.mayoclinic.org/tests-procedures/a1c-test/basics/results/prc-20012585