Disorders of Blood Sugar

Roberto Victor Illa, M.D.

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From our Patient Files

A Patient with Normal A1c but Serious Diabetic Symptoms:
Inadequacy of the A1c for Diagnosis or Treatment

Posted 28 Nov 2007

Last week I saw a new patient, a woman in her early 80s. Her chief complaint was numbness in her feet and pain in her legs, which she has had for five years. She was first diagnosed with diabetes 24 years ago. She was initially treated with diet control. For the past several months she has been treated with Actosplusmet (Actos Plus Metformin) 15/850 combination tablet taken twice daily. She said that over the past two years her diabetes has worsened.

Her HgbA1c was 5.9%, which the is a non-diabetic level. However, her fasting glucose level (measured on the same day as the A1c test) was 120 mg%, while her two hour post-prandial (i.e., after eating) glucose is remarkably high at 193 mg%. (Post-prandial glucose should not be over 140 mg%).

What does this tell us? Keep in mind that the A1c is an average of blood glucose levels over the previous three months or so. (See the discussion of blood glucose meter numbers in the "For Patients" section, at left.) Thus, the A1c is a single number representing the average of weeks of data. In a healthy person, the average will represent a range of blood glucose values that are all quite close to that average, no single reading being either too high or too low. In this patient's case, however, it is apparent that her readings are quite scattered, meaning that although the average is within normal range, the numbers composing that average vary quite widely. For example, she had that 193 post-prandial reading. If this is typical of her post-prandial blood glucose levels, then to have a healthy three-month average, she must also be having many low readings, which are also not healthy. (It is possible that in the days before her laboratory tests were done, her blood sugar levels rose, but this only emphasizes the point that the HgbA1c does not provide information reflective of the current state of pancreatic function). This is simple mathematics. The evidence supporting this mathematical fact is that she suffers from symptoms typical of uncontrolled diabetes: numbness and pain in her extremities. That, and her post-prandal reading of 193, illustrates the inadequacy of the A1c as either a measure of treatment success or as a guide in determining treatment.

I discontinued her Actos Plus Metformin treatment and instead instituted Actos 45 mg once daily only because the patient was also suffering from a common side effect of Metformin, diarrhea. Additional glucose meter readings will be taken before evaluating her need for other medications.

New postings from our files will be added from time to time.