External substances like certain lotions and creams can significantly affect the accuracy of a blood sugar reading taken with a standard finger-prick glucose meter. Accurate blood glucose readings are the foundation of effective treatment, guiding decisions about insulin dosage, diet, and physical activity. When foreign substances mix with the tiny blood sample, they can artificially inflate the glucose result. This contamination can lead to inappropriate treatment choices and poor blood sugar control.
How Skin Residue Interferes with Glucose Meters
Standard glucose meters operate as electrochemical biosensors, relying on a specific chemical reaction to determine the glucose concentration in the blood sample. The test strip contains an enzyme, such as glucose oxidase, which reacts specifically with glucose molecules in the blood, generating an electrical current. When a contaminant is present on the skin, it mixes with the blood drop before the sample is wicked onto the test strip. Many products contain compounds that mimic glucose or interfere with the strip’s chemistry, such as simple sugars or sugar alcohols like glycerin. The enzyme mistakenly identifies these contaminants as blood glucose, resulting in a falsely elevated reading that does not reflect the actual level in the bloodstream.
Common Sources of Blood Sugar Contamination
Contamination often comes from common household and personal care products that contain sugars or sugar-like substances. Lotions and moisturizing creams frequently rely on glycerin for hydration, and this compound can react with the glucose-measuring enzyme on certain test strips. Residue from handling food is another potent source, especially after peeling fruit or consuming sugary snacks. Hand sanitizers can also be problematic, as some formulations use sugar or glycerin as stabilizers, and the alcohol may not remove all residues. Because modern glucose meters require only a minute blood sample, even microscopic amounts of these external sugars can lead to a substantial and misleadingly high result.
Steps to Ensure Accurate Blood Glucose Results
The most effective way to prevent contamination and ensure an accurate reading is to adopt a consistent pre-test cleaning procedure.
Pre-Test Procedure
Before testing, hands should be thoroughly washed using warm water and plain soap for at least 20 seconds. Warm water also helps increase blood flow to the fingertips, which makes obtaining a sufficient sample easier.
After washing, it is important to dry the hands completely with a clean towel. Residual moisture can dilute the blood sample and potentially affect the test strip.
Once the hands are clean and dry, use the lancing device to prick the lateral side of the fingertip, which is less sensitive than the center. Use the first drop of blood for testing, ensuring it is a round, full drop applied immediately to the test strip. Avoid squeezing the finger, as this can introduce tissue fluid and skew the result.