June 13, 2001
Blood Tests and Insulin Injections, Diagnosis and Symptoms
Question from northern Texas, USA:
My eight year old son was diagnosed with moderate hypoglycemia on the basis of a glucose tolerance test. During the test, I ran his levels with my glucose meter after each blood draw, and the two results were drastically different. My high level for him was 271 mg/dl [15.1 mmol/L], and they had 113 mg/dl [6.3 mmol/L]. The last result they got was 73 mg/dl [4.1 mmol/L] and mine was 140 mg/dl [7.8 mmol/L]. This big difference that has me very concerned. I did have my meter checked. Was there an error in the processing of his specimens or does this sound okay?
The differences you describe are indeed very puzzling. We know that there can often be a 10-15% difference between blood drawn from the vein and a finger stick. What you didn’t mention is whether used his finger or an alternate site test. We do see variances widen in some people testing on the arm rather than the fingertip.
You mention that you’ve checked your machine, and I must assume that you have used control solution and tested your strips for accuracy. Have you ever tested your own blood sugar fasting at the lab while doing a finger stick at the same time? These numbers should be very similar and would validate your machine. Finally, I guess I would value the lab results ahead of the meter, but only if the blood sugars were not left to sit for many hours before processing. My final suggestion is to discuss this with your son’s physician and see if there were any reason to redo the tests.