But even this procedure, if done according to careful guidelines, should not cause a problem with the insulin. The other possibility is, as you mentioned, a concentration difference between the first and last withdrawal. In this case thorough, gentle mixing of the insulin at each dosing should prevent a problem. Do observe the expiration dates on insulin and always adhere to them. This is for an adult with diabetes.
Normal ranges can vary depending upon the age and physical condition of an individual.
People with diabetes should set target blood glucose level goals with the help of a diabetes educator or physician. I have been monitoring my blood glucose for about a year. I have read that for my age it should be between 65 and 120. I am on a diet and also walk every day briskly between 3 and 4 miles. The glucose levels that your physician allows are higher than those recommended by the American Diabetes Association, and the range that you report for your personal study may be too low.