Volume 1, Number 3: Fall Equinox, 1999

Introduction to Type 1 Diabetes - BC Diabetes Foundation

Thomas G. Elliott MBBS, FRCPC

University of British Columbia, Vancouver, B.C., Canada


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 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.

Insulin Adjustment

Once your diet and exercise program has become stabilized you will be in a position to consider adjusting insulin to produce sugars in the goal range. Before making any insulin adjustment you should have tested your blood sugar 4 times a day and once at 2-3 am during a minimum 4 day period. You should then calculate the average blood sugar at each time of day and compare those averages to your blood sugar goals. Flag any averages which are outside the goals and determine which outlier is the furthest from the goal. Then adjust the insulin dose that most likely affects that outlier blood sugar. For instance, if you are taking a shot of long-acting insulin at breakfast and bed and a shot of short-acting insulin with breakfast and dinner and your worst high blood sugar is at bedtime you should adjust your short-acting insulin before dinner. Adjust your insulin by increasing (or decreasing) the insulin by 10% rounding up or down as necessary. For example, if you had been taking 10 units of short-acting insulin before dinner you would increase it to 11. On the otherhand, if you were running low at bedtime you would decrease by 1 unit at least. On same insulin regime if you were high at breakfast but okay at 3 a.m. you would increase your bedtime long-acting; if you were high at lunch you would increase your short-acting before breakfast; if you were high at dinner you would increase your long-acting before breakfast. If you were high at 3 a.m. but okay at bed and breakfast you should probably not make any changes. An alternative to increasing your insulin would of course be decreasing your size of the most relevant meal i.e. the proceeding meal (or snack perhaps). You should not make any insulin adjustments if you have had any severe lows during the last several days or if your routine had been very unusual. Insulin adjustment is termed proactive. The intention is produce better blood sugars in the future rather than fixing them right now. See Fig1 and the analysis that follows below for an illustration of how you might record and analyze your blood sugars.

Fig 1 Blood Sugar Tabulation

Blood sugar targets: 5-8 before meals and bed, and more than 5 at 0300 hrs.


Example 1
3 AM Comments
Monday 8.9 13.4 4.2 11.4
Tuesday 12.1 8.8 9.8
Wednesday 10.2 7.6 at Canuck game
Thursday 6.8 7.9 7.2
Friday 9.4 14.6 11.6 10.8 14.5 spaghetti at mom’s
Saturday 10.8 8.4 5.4 10.2
Sunday 8.1 10.9 8.9
Averages 9.4 11.5 7.6 9.4 14.5
Example 2
3 AM Comments
Monday 13.6 8.6 3.8 13.4
Tuesday 18.7 9.6 6.6 4.4
Wednesday 10.4 8.8 21.6 17.0 cinnamon bun at Max’s
Thursday 15.8 19.7 4.3 10.3
Friday 9.1 12.7 7.1 13.3
Saturday 14.4 6.4 16.3 6.5
Sunday 12.9 8.4 4.9 2.8 14.0 swimming after dinner
Averages 13.6 10.6 9.2 9.7 14.0
Example 3
Monday 8.5 15.4 9.3 14.4
Tuesday 10.6 15.8 14.0 18.4
Wednesday 4.2 7.4 16.8 12.2
Thursday 18.6 16.4 15.8 5.3
Friday 3.5 11.1 2.9 12.8 4.8 training at Gold’s
Saturday 3.8 4.1 12.1 13.0 training at Gold’s
Sunday 2.2 12.8 5.3 7.7 training at Gold’s
Averages 7.3 11.9 10.9 12.0 4.8
Example 4
Monday 5.7 2.4 12.8 11.4
Tuesday 11.6 3.9 14.9 6.9 5.0
Wednesday 4.9 3.4 20.6 14.6
Thursday 8.6 3.1 13.7 9.0
Friday 14.8 5.5 15.0 8.5
Saturday 5.5 5.1 9.8 6.1
Sunday 8.1 2.1 14.2 7.0 LO11am mowing yard
Averages 8.5 3.6 14.4 9.1 5.0

Analysis of Fig. 1

Example 1: There are no lows, the numbers are fairly consistent and the average that is furthest from desirable is at lunchtime. Appropriate actions could be either increase short acting insulin before breakfast or reduce the size/type of breakfast or mid-morning snack.

Example 2: There are no lows, the numbers are somewhat consistent, and the average that is most out of range is breakfast. Appropriate action would be to increase evening long acting insulin and test once or twice at 0300 hrs in the following week to make sure there are no lows at that time.

Example 3: Although none of the averages are out of range, the 3 consecutive breakfast lows following training the night before are dangerous. This was despite bedtime readings on the same nights being high. Appropriate action would be to decrease evening long acting on training nights.

Example 4: Lunch readings are consistently low. There was one mild low at 1100 hrs as well. Decrease breakfast short acting insulin or take a bigger breakfast or mid-morning snack.

“One-off” high blood sugars

The notion of “fixing the blood sugar right now” is best tackled by using a “sliding scale”. This refers to taking extra short acting insulin at any one time of day to nominally lower your blood sugar into the goal range. For instance if it is breakfast time and your blood sugar is 12 (goal 4-7) and you normally take 8 units of short acting for breakfast you may decide to take an extra 2 units to do so. There is no perfect sliding scale for every person with diabetes. One very conservative approach to sliding scale follows:

“One-off” high blood sugars

Blood Sugar level Extra Short Acting Insulin
< 3.5 -1 (snack or eat immediately) 
3.5 – 8.0 0
8.1 – 10.0 +1
10.1 – 12.0 +2
12.1 – 14.0 +3
14.1 – 16.0 +4
etc.. Do not ever take more than 6 units of sliding scale unless you have been doing it for some time.

An alternative to taking extra insulin if your sugar is above your glycemic goal would be to do a short amount of exercise. It is fairly simple to learn how much exercise is required to bring your blood sugar down. For instance, on a stationary bicycle for 10 minutes may drop the blood sugar anywhere between 1-4 mmol?L. The virtue of exercise over sliding scale insulin is that you will never suffer from rebound phenomenon. Rebound phenomenon is where you take more insulin than is desirable, then go low and then the blood sugar bounces up as your body struggles to produce glucose. The body’s tendency to prevent hypoglycemia is called counter-regulation and involves the secretion of a number of hormones including glucagon, adrenaline, cortisol and growth hormone. The rebound effects from counter-regulation may last for up to 24 hours after a severe low blood sugar.

“Rules” of Insulin Adjustment

Before you follow the rules below you must be testing frequently and following your meal and exercise plan closely. Generally only one insulin should be changed at a time. Increase or decrease insulin by 10% (or by1 unit if 10% is less than 1 unit). The rules below pertain to individuals taking regular short acting insulin. If you take ultra short acting insulin the rules are slightly different – these are appended later.


Lows always take precedence over highs. Even if you are high some or a lot of the time, If you have lows that are occurring consistently you must avoid them first. If lows are due to exercise, consider only changing an insulin dose (or increase meal or snack) for that specific day or time of day only.

  • Breakfast lows: decrease evening long acting insulin
  • Lunch lows: decrease breakfast short acting insulin (or increase breakfast or mid-morning snack)
  • Dinner lows: decrease morning long acting insulin (or increase lunch or mid-afternoon snack)
  • Bedtime lows: decrease dinner short-acting insulin (or increase dinner or evening snack)
  • 0300 hrs lows: decrease evening long-acting insulin or take evening long acting insulin later (at bedtime if you are taking it before dinner)


Always consider dietary adjustments. If highs are one-off, consider exercising your blood sugar down or using a sliding-scale (see below).

  • Breakfast highs: increase evening long-acting insulin (but check your 0300 hrs test before doing so)
  • Lunchtime highs: increase breakfast short-acting insulin (or decrease breakfast or mid-morning snack)
  • Dinner highs: increase morning long-acting insulin (or decrease lunch or med-afternoon snack)
  • Bedtime highs: increase dinner short-acting insulin (or decrease dinner or evening snack)
  • 0300 hrs highs: no action necessary if breakfast sugar OK (and HbA1c OK), otherwise talk to MD

Ultra-Short-Acting Insulin

Humalog (lispro) is a form of ultra-short-acting insulin that has been modified so that it is absorbed quicker in to the blood stream after subcutaneous injection. In general terms, one unit of Humalog has the same blood glucose lowering effect as one unit of regular (short acting) insulin. After subcutaneous injection it begins to be absorbed within 10 minutes. It reaches its peak effect between 1 and 2 hours and disappears by 4 to 5 hours. Because Humalog is very short acting, between meal snacks are usually not necessary. The likelihood of gaining weight with Humalog therapy is therefore smaller than with regular insulin in a multiple daily dosing schedule. Though I never encourage my patients to miss meals, the chances of severe hypoglycemia when you miss a meal (and of course don’t take Humalog) is much lower than with conventional insulin schedules. This quicker onset and shorter duration of action has some major advantages. The first is that you need not wait after taking your injection to eat. In fact, if you delay eating you run the risk of severe hypoglycemia. If you are forgetful or if there is a chance that you will not eat as soon as expected, it is acceptable to take Humalog after you eat. For the average size meal most people require 2-6 units. You need to experiment to see how much you need based on your body size, how much carbohydrate/starch there is in the meal you are going to eat etc. You should always test before taking your Humalog and give yourself extra sliding scale Humalog if your sugar is higher than your pre-meal target (usually in the range of 5-8). The best way to tell whether you take the ideal amount of Humalog is to test your blood sugar 1-2 hours after you eat. A reasonable target for sugar at this time is 9-10. If your sugar is lower than this you took too much; if it is higher you took too little. The alternative of course is you either ate too little or too much or made poor food choices.

Although using Humalog according to the above recommendations means more testing, it will lead to fewer hypoglycemic reactions, particularly severe hypoglycemic reactions. It will lead to improved HbA1c and ultimately will lead to better quality of life in the short term and fewer complications in the long term.

All patients taking Humalog need to take 2 daily shots of long-acting insulin. The long-acting insulin will be either NPH (N), lente (L), or ultra-lente (U). The best times to take your long-acting insulin is at lunchtime and at bedtime. The advantage of this is that the long-acting insulin typically peaks between 6 and 8 hours – this will be around 5-6 am for the bedtime N and at dinner time for the lunchtime N. The body is resistant to hypoglycemia at 5-6 am and of course your eating at dinner time. The dose of long-acting insulin is adjusted according to the blood sugar before meals. Thus, if the pre-meal breakfast sugar is too high you should probably increase your bedtime long-acting. Before doing so it is wise to test at 3 am to rule out the possibility that your morning high is not due to an asymptomatic early morning low followed by a rebound high. By the same argument, a high blood sugar at lunchtime may mean you need to increase your bedtime long-acting, though if your 2 hour post breakfast is too high then the correct adjustment would be to increase your breakfast Humalog not to increase your bedtime N. Remember you judge your dose of Humalog based on the 2 hour post meal reading. Similarly, a good 2 hour post lunch reading accompanied by a high pre-dinner reading should mean you increase your lunchtime long-acting. Similarly, a good 2 hour post dinner reading accompanied by a high bedtime reading should lead to an increase in the lunchtime long-acting.

A typical insulin schedule using Humalog schedule therefore contains a shot of Humalog before each meal and two shots of long-acting insulin, usually at lunchtime and bed. Most patients following this schedule successfully take roughly 50% of their insulin as Humalog at 50% is long-acting.

Traveling and Humalog

Continue to take your 2 shots of long-acting insulin 12 hours apart whether or not this falls at typical lunchtime or bedtime (this won’t be the case when you cross major time zones). Give yourself Humalog whenever you eat (this is usually frequent on long flights). If you find you are running high between meals give yourself small extra doses of Humalog (say 1-2 units). When you get to your destination gradually adjust your 2 shots of long-acting to conform to the local lunchtime and bedtime. Within a day or two you will be stable.

Insulin Adjustment Software

In collaboration with a young computer programmer who has diabetes and who is also my patient I have developed an insulin adjustment software that runs on IBM compatible computers. It is a DOS based program but does run very well on Windows or Windows 95/98. I would be happy to give you a copy of this software which will make specific suggestions about insulin adjustment. This software will automatically make the most appropriate suggestion.

Driving/Operating Machinery and Diabetes

If you have a severe low while you are driving or operating machinery there is a risk of injury or death to you or others. It is therefore your responsibility that this never happens. You should never drive a car without knowing what your blood sugar is within the last hour or so. If you have had a recent severe hypoglycemic reaction you should test immediately before driving. You should not drive with a blood sugar under 4.5 (under 6 if you have hypoglycemia unawareness, or recent severe low) and you should always carry snacks with you to treat yourself. If you are driving long distances you should stop every hour or two to test your blood sugar. If you have motor vehicle accident with a low blood sugar it is likely that the SuperIntendent of Motor Vehicles will temporarily rescind your driver’s licence. This will necessitate re-certifying through the Diabetes Centre and may cause you to lose your job if it requires driving.

International Travel and Insulin

There is no single or correct way to adjust insulin during long distance air travel, particularly when major time zones are being crossed. In general, the best approach is to continue taking your 1 or 2 shots of long-acting insulin so that you at no time produce ketones. It is best during this sort of travel to take a shot of short-acting insulin before each meal basing the dose on the same criteria mentioned above – size and nature of meal etc. In doubt it is safer to take frequent very small doses of short-acting insulin (taking extra insulin according to a sliding scale every few hours) rather than guessing and giving yourself too much insulin and running low.

Intercurrent Illness and Insulin

During intercurrent illness (colds, flu etc) your body will be less sensitive to insulin and you will therefore require more. The simplest approach is to take the usual amount of long-acting insulin, to test more frequently and to use the sliding scale mentioned above but to give 1 or 2 units more than you would usually give at any one time. Providing you test frequently and do not develop ketones (see below) and give yourself insulin the chances of a significant problem are very small.

Testing Urine for Ketones

You should purchase some ketostix or equivalent from the pharmacy. You should test your urine for ketones if you have 2 or more consecutive blood sugars over 15. If the high sugar is simply due to dietary indiscretion it is very unlikely you will have ketones but if you are feeling unwell then it is likely your body is producing ketones. Should ketones be present in anything other than trace amounts you should test your blood sugar every 2 hours and use a sliding scale of insulin adding an extra 2 units to each sliding scale increment (if you would normally take an extra 4 for a blood sugar of 14.1-16.0 take 6 units instead). If the blood sugar continues to rise and you continue to feel unwell or are vomiting you should go immediately to the nearest Emergency ward. You should also drink copious amounts of sugar-free liquids if you have ketones. You will not feel like eating in any case.

Ketones may also be produced by the body during starvation. This is in fact normal and providing your blood sugar is not over 10 these ketones can be safely ignored if you are starving (or fasting).

Diabetes and the Internet

There are innumerable websites for diabetes information. Some links to other diabetes websites are:

Diabetes and Research

There is a large amount of research being carried out at the Vancouver Hospital and at other centres in Vancouver as well as many studies being done in other centres across Canada, North America and the Western World. There may be a number studies for which you are eligible. Please feel in no way obliged to participate in these studies as they are separate from the clinical relationship you have with me or your diabetes physician.

To facilitate research and education in the diabetes area (and other areas of endocrinology including thyroid, pituitary, women’s health, menopause and osteoporosis, cholesterol and lipid abnormalities) a charity of which Dr. Elliott is the president, the BC Endocrine Research Foundation was established in 1997. The Foundation is always looking for assistance be it either in time as a potential volunteer or financial support. You may discuss this with me at anytime.

Dr. Tom Elliott is an active researcher and educator and the President of the BC Endocrine Research Foundation. He is also a busy physician treating individuals with endocrine disorders.

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BC Diabetes Foundation

#4116 - 2775 Laurel Street
Vancouver, B.C.
V5Z 1M9

Email: info@bcdiabetes.org
Tel: 604-628-2395

Board of Directors

Chair: Dr. Tom Elliott

Board Members: Dr. Keith Dawson, Dr. Breay Paty, Dr. David Thompson, Howard Blank

Administrator: Jack Bondy