Serum Glucose Measurement after Five to Six Hours is Comparable to Eight Hours Overnight Fasting in Ramadan

Objectives: This study was done to evaluate whether a shorter fasting duration of five to six hours can be used as an alternative to the usually recommended eight hours fasting serum glucose measurement. Methods: An observational, cross-sectional study was conducted during Ramadan (May) 2019, on 200 individuals. Two fasting serum glucose (FSG) venous samples taken, the first after 5-6 hours after predawn meal (suhoor), and the second after 8 hours. Participants were divided into two groups; normal individuals, and those who have type 2 diabetes mellitus (T2DM). Patients with T2DM further subdivided into three groups: those without treatment, those on oral antidiabetic drugs (OAD), and those using insulin and OAD. Results: There was no significant difference between the mean FSG readings in mg/dL (mmol/L) between the first and second samples for healthy individuals, 104.5 ± 21.4 (5.79±1.18) and 104.8 ± 12.6 (5.82±0.7), respectively. Generally, the same is true for T2DM patients with FSG values of 235 ± 107 (13.04±5.94) and 230 ± 105 (12.77±5.83). Untreated T2DM patients have consecutive FSG readings of 194.0 ± 151.5 (10.77±8.41) and 193.9 ± 128.9 (10.76±7.15), respectively, in the two samples without significant difference. Patients using insulin and OAD showed similar pattern of FSG 268 ± 111 (14.87±6.16) and 269 ± 114 (14.93±6.33), respectively. The only significant difference was observed in patients on OAD which have 220 ± 78 (12.21±4.33) and 207 ± 77 (11.49±4.27) for their successive FSG samples. Conclusions: The overnight fasting duration of 5-6 hours, can give a comparable measurement of fasting serum glucose as that obtained by 8 hours. Keywords: Glucose; Fasting; Duration; Diabetes Mellitus