Is Plasma Glucose a Better Measure?
When I changed blood glucose meters, the readings were quite different. The company that makes my new meter says it uses a better system based on plasma glucose instead of whole blood. The readings from plasma seem much higher. Is there an exact differential? Is one system better? Joe Veffer, Canal Winchester, Ohio
Roger P. Austin, MS, RPh, CDE, responds:
You have asked an important question, which is often a cause of confusion for people with diabetes who regularly check their blood sugar levels using blood glucose meters.
What to Know: Glucose can be measured in whole blood, plasma, or serum. In the past, hospital laboratories reported blood glucose values in terms of whole blood, but now they more commonly report plasma glucose values. Plasma has a higher water content than whole blood, so there is more dissolved glucose in plasma compared with whole blood, and readings are 15 to 20 percent higher. New blood glucose meters for home use now report blood glucose only in terms of plasma glucose to conform with lab readings.
Possible Solutions: Each manufacturer's blood glucose testing method uses different technology. One is not necessarily better than another—consistency in your checks is what really counts. So, be sure that you use the same meter as much as possible when you check and record your blood sugar readings. Some people may use one meter at home and a different one at the office. Comparing blood glucose results from two or more meters is like comparing apples and oranges; they are not equivalent.
Takeaways: You can take other steps to improve the accuracy of your blood glucose readings. Store meters and strips where they won't be exposed to extremes in temperature or humidity. Before taking a reading, thoroughly wash your hands with soap and warm water (alcohol is not necessary), and dry with a clean towel. Food residue, creams, lotions, or perfumes on your fingers can affect your reading. Finally, know that a finger stick check, while very useful, is a "snapshot" of your glucose level and may change quickly.