Q: Will there be any side effects or complications if we use only one kind of insulin for a long time? Do we have to change insulin once in every 2 or 3 years. My father is a type 2 diabetic patient for the past 8 years now. He is 53 years old, and he has stopped taking any oral medication but he is taking insulin human mixtard for the past 2 years and has absolutely controlled blood sugar. Is it ok if he continues to use insulin? Also are urine glucose and blood glucose levels comparable?

A:There are many types of insulin products available in four basic forms, each with a different time of onset and duration of action. The decision as to which insulin to choose is based on an individuals lifestyle, a physicians preference and experience, and the persons blood sugar levels. Among the criteria considered in choosing insulin are: a) How soon it starts acting (onset) b) Time when its action is maximum (peak time), and c) How long it's effect lasts in the body (duration). The insulin preparations are either taken from animals (pigs or cows - porcine or bovine) or synthesised in labs to be identical to human insulin. There is a gradual shift from animal based products to human recombinant forms. The human insulin is manufactured by inserting portions of DNA (recombinant DNA) into special lab-cultured bacteria or yeasts, which then produce complete human insulin. Recently, insulin products called insulin analogues have been produced, whose structure differs only slightly from human insulin (by one or two amino acids) but changes the onset and peak of action. The onset, peak, and duration of action for each insulin product varies depending on each individual, the injection site, and the individuals diet and exercise program. Insulin may be used acutely for newly diagnosed symptomatic patients and is used on a long-term basis after maximal oral antidiabetic therapy has failed to achieve adequate control. The type of insulin and the frequency of administration depend on the blood glucose patterns (usually self-monitored values), especially the post-prandial sugar levels. A close and regular follow-up is required to adjust insulin doses and monitor progress. Commonly used insulin preparations are short (or rapid), intermediate, and long-acting, and mixtures of these. Rapid-acting insulins are used whenever quick glucose utilisation is needed (eg, before meals or when the blood glucose level is >250 mg/dL). The onset of action is 0.5-1 h, peak effect in 2-3 h; usual duration of action 8-12 h. Intermediate-acting insulins have a relatively slow onset of action and relatively long duration of action. They are usually combined with faster-acting insulins to maximise benefits of a single injection. The onset of action 1-1.5 h, peak effect in 4-12 h and usual duration of action 16-24 h. Long-acting insulins have a longer duration of action and, when combined with faster-acting insulins, offer improved glucose control for some patients. The onset of action is 4-8 h, peak effect is in 16-18 h, and usual duration of action is >32 h. Various insulin regimes are employed and usually a mixture is used for better sugar control. Which insulin is to be continued in your father’s case depends on his sugar level and your doctor is best placed to advise. Urine sugar tests are not as accurate as blood sugar tests and provide only a rough estimate of blood sugar level. Glucose will overflow into the urine only when the blood glucose level is high, that is, too high for the kidneys to stop it spilling over into the urine. In most people, blood glucose levels above 180 mg/dl will cause glucose to appear in the urine. This level is called the ‘renal threshold’ for glucose. Thus, blood sugar level may be high and yet not detectable in urine. On the other hand, the renal threshold for glucose can be lower in some people who are otherwise healthy, during pregnancy, and in people who have a kidney disorder. In such instances glucose may be present in the urine despite the blood glucose being normal making interpretation of test results difficult. Moreover, urine glucose test does not reflect the blood glucose level at the time of testing; instead, it gives an indication of blood glucose level over the past several hours. For example, some of the urine present in the bladder may be 2 hours old, and may show glucose even though the blood glucose may have normalised since then. In contrast, blood glucose gives an idea of the current blood glucose level. Also, urine sugar level does not give any information about low blood glucose levels, as glucose is only found in the urine when the blood glucose level is above 180 mg/dl. In other words, a negative urine glucose test may be the result of a normal blood glucose level or a dangerously low blood glucose level, with the urine glucose test unable to differentiate between the 2 situations. The urine sugar results are influenced by the volume and concentration of urine and will vary with the amount of fluid consumed and fluid loss due to sweating or vomiting.