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August 15, 2001

Diagnosis and Symptoms, Other Medications

Question from Phoenix, Arizona, USA:

During two hospital stays, an 84 year old had two fasting blood sugars of 136 and 168 mg/dl [7.6 and 9.3 mmol/L] having had no abnormal readings previously. I questioned it then, but was told in someone her age, it was no big deal. I recently asked her primary care physician to run some lab work which resulted in an A1c of 5.5% and a non-fasting glucose of 202 mg/dl [11.2 mmol/L]. She is not overweight and her diet is excellent. Her intake of simple sugars, cakes, pies, candy, etc., is practically nil. She eats three balanced meals daily. Blood pressure and heart problems are new within the last nine months. Is a finding such as this common in someone her age? We have an appointment to see the doctor next week. She is several medication including HCTZ (12.5 mg, every other day) [hydrochlorthiazide, a diuretic] which (so I have read) can raise glucose levels. Is the information I read about HCTZ accurate? If so and she stops this medication, is it reasonable that we see a decrease in blood sugars or has some process been set into motion which cannot be stopped? How long after discontinuing a medication will results show?

Answer:

You have raised several good questions which are quite common in clinical practice. First, the fasting blood sugars you mentioned, if performed in a certified lab, are consistent with the diagnosis of type 2 diabetes. The criterion is two blood sugars greater than 126 mg/dl [7 mmol/L] on separate occasions. Second, at age 84, it is unlikely that this degree of blood sugar elevation will result in long-term complications because of the person’s advanced age. However, it is worth monitoring because even elevated blood sugars for a short time can impact healing and weaken the body’s defenses against infection.

Second, the hemoglobin A1c provides a number which correlates with the average blood sugar over the previous three months. If the elevated blood sugars are of recent onset, the hemoglobin A1c may not be elevated. It has also been shown that the hemoglobin A1c is not sensitive enough to diagnose diabetes.

Third, it is true that HCTZ has been shown to promote diabetes. It is thought to do this through its effect of inducing low potassium levels in the blood. Doses above 25 mg are more likely to elevate lipids and cause elevated blood sugars. At a dose of only 12.5 mg on alternate days, it is unlikely that this dose would precipitate the diabetes.

I would recommend discussing these issues with the primary physician in order to develop a management strategy which addresses both problems.

JTL