April 13, 2003
Question from Hastings, Florida, USA:
I am 33 years old, 30 weeks pregnant with my third child, and during my first two pregnancies, I failed the initial one-hour glucose testing but passed the three-hour tests. I was not at all surprised to fail the initial test with this pregnancy and had no worries about the three-hour test. During my first two pregnancies, the test was done by drawing blood, but with this pregnancy, the three- hour was done by finger stick and the results were instant.
I had a fasting level of 78 mg/dl [4.3 mmol/L], a one-hour level of 199 mg/dl [11/1 mmol/L], a two-hour level of 145 mg/dl [8.1 mmol/L], and a three-hour level of 47 mg/dl [2.6 mmol/L]. My doctor says that technically I passed but wants me to seek counseling for gestational diabetes anyway because of the one-hour reading. I myself was more concerned that the three-hour was so low because, within 10 minutes of leaving the office, I broke out in a terrible sweat and began to shake uncontrollably until I was able to get some food in my system.
I have since received a call from the hospital to schedule an appointment for my gestational diabetes. Do these numbers put me in the classification of having gestational diabetes? Are the fingerpricks as accurate as drawing blood from the arm? Is the 47 mg/dl [2.6 mmol/L] at three hours result normal? Should there be concern there?
The blood glucose testing should be based on venous sampling not fingerstick values. There is a greater amount of variation with fingerstick measurements. Nevertheless, the one hour value is high and some dietary adjustment may be worthwhile even though you do not meet criteria for gestational diabetes. The three hour result is low, but probably transient. I would not be concerned about it.
[Editor’s comment: Your sweats and shakes and need for food strongly suggest the three-hour value was low and you had hypoglycemia. But as Dr. Jones points out, you needn’t worry much about having such symptoms regularly, as the GTT is such an artificial situation.