The US uses blood sugar readings in units of milligrams per deciliter (mg/dl). Australia and most European countries use the metric measure of millimoles per liter (mmol/l). Conversion between the two unit measures is done by a factor of 18. You convert mg/dl to mmol/l by dividing the mg/dl measure by 18.

Your post-meal blood sugar may or may not be abnormal depending upon the timing of when you took the blood sugar. The standard method for diagnosing diabetes or other blood sugar problems is either an overnight fasting blood sugar or as you mentioned above an oral glucose tolerance test.