The basic examinations of diabetes mellitus in clinic are determination of blood sugar and urosaccharometry. The normal reference index of blood sugar is 3 .8 – 6 .1 mmol / L at fasting and less than 7 .8 mmol / L 2 hours after meal . If the urinary excretion of glucose exceeds
150 mg / 24h, positive reaction may show in urosaccharometry . The glycosylation hemoglobin reflects the blood sugar level in previous 4 – 8 weeks . The normal value of glycosylation hemoglobin is less than 7% . More than 8% belongs to abnormal, and more than 12% can be diagnosed as severe sustained hyperplycemia . Generally speaking, glycosylation hemoglobin reflects the blood sugar level of the subject in the previous 1 – 3 weeks . Glycosylation hemoglobin is an ideal index for diagnosing and monitoring diabetes mellitus because of its accuracy, simplicity and no diet limitation. In oral glucose tolerance test for normal persons, usually the concentration of blood sugar in plasma reaches its peak after 30- 60 min, but the level of blood sugar does not go up over 11 .1 mmol / L . From then on, it decreases rapidly to normal level within 1 .5 – 2 hours . For patient with gastro-in-testinal dysfunction, the absorption may be influenced . Therefore, it is better to use intravenous glucose tolerance test . Plasma insulin determination and insulin release test can reflect the function of patient’s islet cells.
Normal persons plasma insulin on an empty stomach is 5 20 mU/ L . After meal , five to ten times it will raise . The excretion peak occurs thirty to sixty minutes after meal . The C peptide determination is not interferenced by exogenous insulin and insulin antibody . It is suitable
for the patients who receive insulin treatment . Normal persons serum C peptide on an empty stomach is 0 .56±0 .29 mmol / L .
WHO Criteria for Diagnosing Diabetes Mellitus which is extensively used by various countries in the world:
1 . fasting blood sugar ≥7 .8 mmol / L
2 . anytime blood sugar ≥11 .1 mmol / L
One of the aforesaid items can establish the diagnosis of diabetes mellitus .
In the practice of Differential Diagnoses, the following disorders should be differentiated from diabetes mellitus: Liver diseases, renal diseases, endocrine diseases ( such as diabetes mellitus insipidus, hyperthyroidism, acromegaly , Cushings disease, islet cell tumor, etc . ) , obesity , gout, stress condition, drug-induced hyperglycemia on empty stomach or decrease of glucose tolerance.