Effect of Alcohol Swab on Blood Glucose Readings Using a Glucometer: A Quasi-Experimental Study

Background Although alcohol swabs are commonly used to disinfect the skin before capillary blood glucose testing, there is inconsistent evidence regarding their actual impact on glucose readings. Some studies have suggested that residual alcohol may lead to falsely elevated results, while others have found no significant effect. This study aimed to evaluate the impact of various finger-cleaning techniques on capillary blood glucose readings obtained using a glucometer. Methods A quasi-experimental design was conducted among 249 adult participants attending primary health care centers in Al-Ahsa, Saudi Arabia. The study was conducted between July and September 2025. For each participant, baseline glucose levels were first measured after standard handwashing using capillary sampling. Participants were then divided into three groups: those who washed their hands with water and were tested after their hands had been dried, those whose fingers were disinfected with 70% alcohol and tested while still wet, and those whose fingers were disinfected with 70% alcohol and tested after complete drying. Capillary blood was collected under each condition by trained healthcare providers and analyzed using a calibrated Accu-Chek Instant glucometer (Roche Diagnostics, Germany). Results The participants had a median age of 35 years (interquartile range [IQR]: 26-44), and 57% (n = 141) were female. Most participants (90%, n = 225) reported no underlying health conditions. The comparison of blood glucose readings revealed no statistically significant differences between the blood glucose levels measured at baseline after handwashing using capillary sampling and both the hand wash intervention (95, 89.5-103 mg/dL; p = 0.873) and wet-alcohol finger groups (95, 86-107 mg/dL; p = 0.735). However, the dry-alcohol group (98, 91-109 mg/dL) demonstrated higher readings (p = 0.028). Overall, the Kruskal-Wallis test indicated no significant difference in glucose levels among the three intervention groups compared to the baseline level in each participant (p = 0.325). Conclusions The study's findings indicate that the blood glucose level is not significantly impacted by cleaning the fingertip with or without an alcohol swab before blood glucose testing, regardless of whether the alcohol is allowed to dry completely. Thus, using alcohol swabs to disinfect hands remains a safe and effective method for both clinical and home glucose testing.