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

OBJECTIVES: This study aimed to evaluate whether a shorter fasting duration of five to six hours can be used as an alternative to the usually recommended eight hours for fasting glucose measurement. METHODS: This one-month observational, cross-sectional study was conducted during Ramadan (May to June) 2019. It included those attending Faiha Specialized Diabetes, Endocrine and Metabolism Center, Basrah, Iraq; all individuals ate a pre-dawn meal (suhoor) followed by a complete fast for many hours. Two fasting serum glucose (FSG) venous samples were taken; the first was taken five to six hours and the second eight hours after the pre-dawn meal. Participants were divided into two groups: individuals with type 2 diabetes mellitus (T2DM) and those with a normal glucose level. T2DM patients were further subdivided into three groups: those without treatment, those on oral antidiabetic drugs (OAD) and those using insulin and OAD. RESULTS: A total of 200 individuals participated in this study. There was no significant difference found between the mean FSG levels in the first and second samples for those without T2DM (104.5 ± 21.4 mg/dL versus 104.8 ± 12.6 mg/dL; P = 0.80) as well as those with T2DM (235.0 ± 107.0 mg/dL versus 230.0 ± 105.0 mg/dL; P = 0.20). Untreated T2DM patients had non-significant FSG readings for the two samples (194.0 ± 151.5 mg/dL versus 193.9 ± 128.9 mg/dL; P = 0.90). Patients on insulin and OAD showed a similar pattern of FSG (268.0 ± 111.0 mg/dL versus 269.0 ± 114.0 mg/dL). However, the two FSG samples were found to be significantly different among patients on OAD (220.0 ± 78.0 mg/dL versus 207.0 ± 77.0 mg/dL; P = 0.01). CONCLUSION: The fasting duration of five to six hours can give a comparable measurement of FSG as that obtained after eight hours.