When should I check my blood sugar levels? The answer is now! As a matter of fact, th answer on the question “When should I check my blood sugar levels” can be only “now” or “as soon as possible, but better do it now”. Blood sugar level before eating should be measured first using glucometer for probable symptoms of Type 2 diabetes disease. Then blood sugar levels must be checked again after a meal. High glucose levels are usual flag for symptoms of Type 2 diabetes.