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HA1c : Just the Tip of the Iceberg?

In medicine, we necessarily rely on making diagnoses which rely heavily upon objective data, laboratory values, normal values, and labels. Treatments are frequently prescribed based on these cutoff values, and patients and physicians alike rely on follow up laboratory values to assess the success of the treatments and assume future risk based on those values. But, what if those assumptions are wrong or incomplete? In medicine, there are examples of where, in hindsight, common practices were determined to be incorrect or incomplete. It is known that it can take years for physicians to change ingrained habits even after new research shows new information. Sometimes, the hardest changes are those that go against what seems like “common sense” or to follow “logic.” Two examples of this that come to mind are hormone replacement therapy for post menopausal women and blood transfusions in the treatment of childhood acute leukemia. Since men tended to suffer heart attacks a decade earlier than women, it was thought that estrogen protected women against heart attacks, and hormone replacement therapy for menopause was commonplace. Then, the Women’s Health Initiative study was stopped early in 2005 as it showed increased risk of heart disease, stroke, and dementia. Another example of an unexpected result in a medical trial occurred when a cohort of patients being treated for acute leukemia refused transfusions of blood products and actually had improved survival compared to those that had the recommended transfusions. This happened a long time ago, and the trend of patients having improved outcomes with less transfusions has been repeated in cardiac surgeries and other settings as well. But, how does this relate to Rainier Medical? Well, it is the heavy reliance on the hemoglobin A1c (HA1c). A HA1c is a measure of the amount of glucose attached to hemoglobin. This happens when the amount of glucose is above normal in the blood. When I started residency, HA1c was new, and we still used frequent blood sugar testing and glucose tolerance tests when controlling diabetes. However, these days, it seems like the HA1c is much more commonly the main parameter upon which treatment decisions are based. Indeed, people who have diabetes sometimes do not check their blood sugar at home and instead rely on the HA1c, which is not necessarily against medical advice. This leaves me with three concerns which I think are sometimes overlooked:

  1. For people on no medication for diabetes, the HA1c does not show how hard the pancreas is working to maintain blood sugar control.

  2. Because a HA1c shows an average blood sugar, it does not give information about the variability of blood sugar.

  3. For people on medication for diabetes, tight control of the HA1c can have risks.


Let’s look at these potential pitfalls more closely and what you can do to make sure you are addressing everything you can for your current and long term health:


Scenario 1: HA1c<5.7, On no diabetes medications:


In this scenario, your HA1c is in the normal range, which is excellent, but you may still have a high insulin level to achieve this normal blood sugar average. Why does this matter? Well, for 2 reasons: (1) it can lead to “burn out” of the liver and pancreas, and (2) the high insulin level can lead to chronic inflammation and adverse health consequences. How can you tell if this is happening? You can get some clues by measuring a fasting plasma insulin level. If it is under 7-10, this is normal. You can also calculate a “HOMA-IR” score, using a fasting insulin and a fasting glucose level drawn at the same time. You can estimate your risk without blood work by calculating your waist to hip ratio.