Approximately 6% of non-obese and 2% of obese Type 2 diabetic patients need to start insulin each year. Predicting the need for insulin is difficult: those of lean body mass, especially in the presence of islet cell antibodies, are at greatest risk.
Whether to give insulin to Type 2 diabetic patients is one of the most important yet difficult decisions to be made in treating these patients. Failure to give insulin to some patients results in protracted and needless malaise if not actual danger. On the other hand, giving insulin inappropriately can cause needless problems, notably from hypoglycaemia and weight gain.
Indications for giving insulin to Type 2 diabetic patients who are inadequately controlled despite adherence to their recommended diet and oral hypoglycaemic agents are as follows:
• Continuing weight loss (even if this is insidious), and persistent symptoms, or both. Insulin treatment in these patients almost always results in a substantial improvement in health.
• A non-obese patient without symptoms whose weight is stable and who is conscientious with existing medication. Diabetic control will usually improve, and about half of the patients will enjoy an improvement in well-being.
• An obese patient without symptoms whose weight is stable presents an even more difficult problem. The correct management is to ensure that they are taking their medication, together with intensification of diet, but sometimes insulin may be needed simply to improve control of diabetes in order to reduce long-term complications during the following decade or more. A reduction of HbA1C of approximately 2% together with weight gain of around 5-7 kg can be expected. Unfortunately improvement in glycaemic control is not always achieved. Patient choice is important here, and some prefer not to take insulin after all explanations have been presented. Reluctant patients can be
• Alcohol can cause serious hypoglycaemia when used with sulphonureas and lactic acidosis in those taking metformin
• Aspirin, sulphonamides, and monoamine oxidase inhibitors may enhance the hypoglycaemic action of sulphonylureas, but in practice problems are rarely seen
• Selective serotonin reuptake inhibitors used in the treatment of depression may provoke hypoglycaemia
• Serious hyperglycaemia is provoked by corticosteroids, dopexamine (inotropic support agent) and intravenous P agonists (salbutamol, terbutaline, ritrodrine)
• Thiazide diuretics (other than minimum dosage, for example, bendrofluazide 2-5 mg) can exacerbate hyperglycaemia
• The immunosuppressive drug ciclosporin can also exacerbate hyperglycaemia
• Protease inhibitors used in the treatment of patients with HIV can cause a syndrome of lipodystrophy, hyperlipidaemia, and insulin resistance leading to severe exacerbation of hyperglycaemia or even causing diabetes
• Clozapine may provoke hyperglycaemia
• P blockers may exacerbate hyperglycaemia or hypoglycaemia depending on dose, concomitant medication, nutritional state, severity of illness, and the patient's age
• Other less common drug interactions are described in the BNF
Indications for insulin in Type 2 diabetes
• Insulin is usually contraindicated in overweight patients whose weight is increasing—giving insulin will make this worse
• Patients who continue to lose weight usually need insulin
• Achievement of tight control in order to prevent complications is obviously more appropiate in younger than in older patients, so the patient's age needs to be considered in deciding whether or not to start giving insulin
• Many older patients, however, benefit greatly from insulin treatment, with an improvement of well-being, and insulin should not be withheld on grounds of age alone
Indications for insulin in Type 2 diabetes mellitus
Diet Poor control Sulphonylurea
No weight loss
Trial of insulin
Low calorie diet
No weight loss
No weight loss
Further dietary advice given a three-month trial of insulin and then make their decision, which experience shows to be usually affirmative. Those with a short life expectancy do not necessarily benefit, and those with other medical disorders will require individual consideration. • Insulin is often required in patients with intercurrent illness. Many disorders, notably infections, increase insulin resistance, leading to the temporary need for insulin. Withdrawal of insulin after recovering from the illness is important provided adequate control is achieved and maintained.
Corticosteroids always exacerbate hyperglycaemia and often precipitate the need for insulin. This should not deter doctors from prescribing them when they are needed.
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