Introduction Self-monitoring of fasting, pre and postprandial blood glucose (SMBG) is an integral part of diabetic care. The validity and accuracy of different glucometer types vary significantly and at present, none of the local authorities carry out pre or post marketing evaluation of these devices in Sri Lanka. This study evaluated the accuracy and validity of 3 types of SMBG devices available over the counter, Device 1, Device 2 and Device 3 against a standard laboratory reference method. Methods A random sample of 103 capillary and venous blood samples were analyzed from diabetic pregnant patients admitted to Teaching Hospital Peradeniya for Blood Sugar Series Testing. Haematocrit value was also obtained by microhaematocrit method. Analytical and clinical accuracy were determined. Results The correlation coefficiencies were 0.856, 0.880 and 0.873 for Device 1, Device 2 and Device 3, respectively. Only Device 2 met the International Standardization Organization (ISO) performance standards for glucometers for glucose values >100 mg/dL whereas none of them met the ISO criteria for values <100 mg/ dL. In surveillance error grids, 87.8%, 93.3% and 81.6% of the data points were within non risk zone for Device 1, Device 2 and Device 3 whereas 11.1%, 4.4% and 17.2% were within slightly lower risk hypoglycemia area. All types of glucometers were less reliable in detecting hypoglyacaemia. Conclusions The over the counter SMBG monitoring systems are encountering certain problems in terms of accuracy and validity. Clinicians should exercise caution in making clinical decisions based on glucometer values for diabetic pregnant patients.