Glycated hemoglobin, also known as HbA1C, has long been touted as the gold standard for diagnosing diabetes. If your HbA1C is above 5.0%, some experts opine, or 7.0%, in the opinion of others, then you need to start practicing blood control. But HbA1C is a problematic measurement.
HbA1C is a measurement of the percentage of red blood cells that have bonded to glucose. The higher your blood sugar levels, the more red blood cells that sugar-coated. This glycation of the red blood cell continues throughout its life cycle, so HbA1C is thought to be a good measurement of the average blood sugar level over the last 90 to 120 days, the average life span of a red blood cell.
Except when it isn't.
Dr. Joyce Lee of the Mott Children's Hospital at the University of Michigan questions the diagnostic value of HbA1C in detecting diabetes in teens. Young people in their growth spurt are increasing their volume of blood, effectively diluting the percentage of red blood cells that is glycated. If a child has risk factors for diabetes, such as family history and overweight, then some other test is indicated.
Like a finger stick while fasting in the morning and a finger stick 120 minutes after a meal. Sometimes the most useful technology is not the most expensive.
Just taking a fasting blood sugar level, by the way, is not necessarily a good way to test for early type 2 diabetes. The ability of the pancreas to handle "phase 1" secretion, producing insulin right after a meal, is usually the first to go.
High blood sugar readings right after meals are a better indication of incipient diabetes than high blood sugar readings first thing in the morning, because even a sick pancreas sometimes can can catch up overnight. But HbA1C is not the best way to measure this.