Introduction

Type 1 diabetes or insulin-dependent diabetes mellitus, is caused by the destruction of the beta cells, the cells in the pancreas which produce insulin. As insulin levels fall, blood sugar (glucose) rises. The destruction of the beta cells is mediated by the immune system. The trigger for this process is unknown but is felt to be related to viral infections and/or exposure to various antigens in the environment. By the time diabetes develops, fewer than 5% of the beta cells remain functional and within 5 years there is zero function. In the first year or two after diagnosis of diabetes the insulin requirement may decrease dramatically or even disappear. This is called an insulin "honeymoon" and is related to rejuvenation of some of the near-dead insulin secreting cells. Unfortunately, these "honeymoons" are shortlived, lasting 3-12 months.

The problem with diabetes is that if blood sugar is allowed to be significantly above normal for many years irreversible damage to the eyes, kidneys, nerves and blood vessels may result leading to significant disability or even death. If blood sugar can be kept close to normal throughout life, not only will you have very good quality of life but your life expectancy should be no different to people who do not have diabetes. The key to controlling diabetes is to learn to closely regulate diet, exercise, insulin administration and blood glucose testing.

Insulin

Insulin causes glucose to enter cells where it then provides energy for metabolism and growth. Insulin need only be present in fairly small amounts for this to occur sufficient to maintain life. However, if insulin levels are allowed to fall further the liver produces ketones which if allowed to accumulate cause acidosis, severe illness and even death. In the pre-insulin era (prior to 1922) all patients with your type of diabetes were dead within 12 months because of the overproduction of ketones. It is therefore necessary that small amounts of insulin be present in your blood at all times to prevent ketone production. This is achieved in clinical practice by giving 1 or more (usually 2) shots of long-acting insulin.

Long-acting insulins are called variously N (NPH), U (or ultralente), or L (lente). They typically enter the bloodstream after being injected into the skin at about 1 hour, peak at 4-10 hours and generally leave the system at around 14-20 hours. The dose of long acting insulin is generally adjusted so that your blood sugar is in the desirable range after periods of fasting or in the late afternoon before the evening meal.

Short-acting insulin comes in 2 forms - R (or regular, fast, soluble, clear, or Toronto) which enters the bloodstream after about 30 minutes, peaks at 2-4 hours and is gone by 6-8 hours and H (humalog) which enters the bloodstream at about 10 minutes, peaks at 45-90 minutes and is gone from the system in 3 to 4 hours. Short-acting insulin is generally given prior to a meal in doses sufficient to produce a normal sugar before the next meal (R) or 2 hours after the meal (H). The dose of short-acting insulin is adjusted based on a) the size and nature of the meal about to be taken, b) how high the blood sugar is prior to the meal, c) the expectation of exercise following the meal and d) presence or absence of illness (your insulin is generally slightly less effective and therefore you need higher doses). Because short acting insulin peaks generally after the stomach is empty and therefore peaks when there is little food to be absorbed, it is necessary to take snacks between meals. Therefore 3 snacks a day are generally necessary - between mid-morning, mid-afternoon and before bed. Without these snacks low blood sugar (hypoglycemia) may occur. Hypoglycemia is potentially very serious as sugar is the fuel of the brain. Without adequate fuel the brain works less well or may stop working completely. This may cause lack of concentration, decreased attention, confusion, seizures, coma or even death. Hypoglycemia is treated by consuming small quantities of sugar of highly refined carbohydrate.

Blood Glucose Testing

Blood glucose testing is necessary to determine the correct dose of insulin, the adequacy of the diet and the effects of exercise or illness upon blood sugar. Testing blood before each meal, at bedtime daily and at 3 a.m. once a week or so is ideal. In practice blood sugar may be tested less frequently but only once good blood glucose control is well established. Blood sugar may also be measured after meals, though it is difficult to control blood sugar swings after meals unless you take H insulin which currently is rather expensive and generally not indicated for most people with Type I diabetes. Blood sugar goals before meals should be 4-7 mmol/L (70-130 mg/dl). Bedtime goal should be 5-8 (90-145) and at 3 a.m. >3.5 (80). If you decide to test 2 hours after meals reasonable goals are <7 (125). Your physician will assess your longterm blood sugar control using a test called HbA1c. The level of HbA1c is a guide to blood glucose control over the previous 8-10 weeks. Values in people who do not have diabetes are 0.048-0.062. In people with Type I diabetes values < 0.073 are regarded as optimal, 0.073-0.080 as moderate, 0.081-0.090 fair and > 0.090 poor or compromised. It is well established that the risks of longterm complications of diabetes in patients with optimally controlled blood sugars are half those of patients with poorly controlled blood sugar.

Living with Diabetes

Over the periods of weeks and months you will learn to live with your diabetes. This will be a slow process of gradual adaptation and it will be tough but ultimately will bring rewards to you. Your physician and members of the diabetes care team will work closely with you to help you become master of your diabetes and lead a full and healthy life.