By Gary Scheiner, MS, CDE | April 23, 2008 12:00 am
Is it really possible to have too much of a good thing? Take my own “good things” list as an example. I really enjoy taking my kids to ballgames, eating popcorn at the movies, and lying on the beach. Good things, yes, but only in moderation. If left unchecked, I might become broke, obese, and badly sunburned.
For millions of people with diabetes, insulin and oral medicines that stimulate the pancreas to release more of its own insulin are good things. Without them, blood glucose levels would become wildly out of control. But when taken in too great a quantity, they can produce the opposite extreme: low blood glucose, or hypoglycemia.
Physicians usually advise people to avoid blood glucose levels below 60 or 70 mg/dl (it varies depending on which book you read and where your health-care provider studied). At this low level, many of the body’s key organs, especially the brain and nervous system, become deprived of the fuel they need to function properly.
Hypoglycemia presents a serious threat to a person’s physical, intellectual, and emotional well-being. It has been called the “greatest limiting factor” in diabetes management. Were it not for the risk of hypoglycemia, a person with diabetes could simply load up on insulin or pancreas-stimulating medicines to keep his blood glucose level from ever rising too high. Unfortunately, hypoglycemia does exist, and it creates a number of problems.
First and foremost is the risk to one’s personal safety. The brain is one of the first organs to be affected by low blood glucose. When the brain receives inadequate fuel, confusion and poor decision-making often result. This can easily lead to life-threatening accidents, loss of consciousness, coma, and possibly even death if left untreated for too long.
Personal performance is another area affected by hypoglycemia. The ability to perform in sports, school, work, and social situations is affected negatively by low blood glucose. In many ways, having low blood glucose is similar to being drunk: It affects our movements, our thoughts, and virtually everything we say and do.
The brain’s ability to detect low blood glucose is an important protective mechanism. However, this mechanism is blunted by repeated bouts of hypoglycemia. With each low, the brain becomes less and less sensitive to the lows — perhaps not recognizing them at all. Without the brain’s reaction to the low, a person with diabetes may remain completely oblivious to the problem. This condition, known as hypoglycemia unawareness, puts a person at risk for severe hypoglycemia (leading to loss of consciousness, etc.) because of the lack of an “early warning” system.
In extreme cases, hypoglycemia can even cause permanent brain damage. With every episode of hypoglycemia, some brain cells die. Considering that you start with billions of brain cells, losing a few here and there is not likely to make any significant difference. However, repeated bouts of severe or prolonged hypoglycemia have the potential to create noticeable cognitive deficits.
In many instances, low blood glucose also causes anxiety or embarrassment. Some people with diabetes worry about the impression left on others by a hypoglycemic episode. Does it make me look sick? Different? Like I’m not “in control”? The fear of experiencing hypoglycemia in a social setting leads many people toward the opposite extreme: maintaining high blood glucose levels around the clock.
Because of the need to eat extra food to treat low blood glucose, weight gain can also become an issue. Hypoglycemia can produce a werewolf-size appetite, resulting in the consumption of excessive calories for several hours. If low blood glucose occurs frequently or is consistently overtreated, weight gain will likely result.
Additionally, did you know that low blood glucose can produce significant highs? A rebound, as this is called, is the body’s natural hormonal response to the low. Once hypoglycemia is detected by the brain, adrenaline starts to flow into the bloodstream along with other blood-glucose-raising counterregulatory hormones such as cortisol and glucagon. Collectively, these hormones stimulate the liver to release stored glucose, which can cause blood glucose to stay high for many hours following a bout of hypoglycemia.
With the current state of medical technology, it is usually not realistic to achieve tight blood glucose control without any episodes of hypoglycemia. This holds true for everyone with Type 1 diabetes and many people with Type 2 diabetes who use insulin or pancreas-stimulating oral medicines. All types of insulin as well as the following oral medicines can cause hypoglycemia:
(Combination medicines that contain sulfonylureas, such as Glucovance, Metaglip, Avandaryl, and Duetact, and combination medicines that contain meglitinides, such as Prandimet, can also cause hypoglycemia.)
So what is realistic? For starters, accept that an occasional low can occur. It is reasonable to experience mild low blood glucose a couple of times each week — lows that you can detect and treat without outside assistance. It is never acceptable to experience a severe episode of hypoglycemia (a low that causes a loss of consciousness, seizure, or unresponsiveness). Following any low that requires emergency medical assistance, additional self-management education and greater attention to control is always in order. A change in therapy may also be necessary.
If you check your blood glucose at each mealtime and bedtime, try to have no more than 10% of your readings below 70 mg/dl (or 80 mg/dl for very young children) at each test time. For example, let’s say you collect your readings for an entire month (31 days) and find the following:
Before breakfast: 3 lows (10%)
Before lunch: 2 lows (6%)
Before dinner: 0 lows (0%)
Bedtime: 5 lows (16%)
The conclusion would be that there are too many lows at bedtime. A reduction in the dinnertime insulin (or oral medicine) may be in order. The number of lows at breakfast, lunch, and dinner appears to be acceptable.
For people with Type 2 diabetes, multiple episodes of hypoglycemia are a sign that insulin and/or oral medicines should be reduced. This, in turn, will help with any weight-loss efforts. In addition, people with existing heart disease should try to avoid hypoglycemia entirely. If you have heart disease, let your doctor know if you experience any lows.
Part of avoiding low blood glucose involves — how shall I put this? — just dumb luck. That’s why it is usually considered acceptable to have lows up to 10% of the time. But the majority of hypoglycemia avoidance is well within your control. My top 10 strategies for preventing lows are as follows:
1. Match your insulin or medicine program to your needs.
The “peaks and valleys” in your insulin should coincide with the peaks and valleys in your blood glucose levels. This usually means utilizing a basal–bolus insulin approach — having a long-acting, or basal, insulin working at a low level throughout the day and night, and rapid-acting, or bolus, insulin at each meal or snack. Most adults experience a dawn phenomenon, in which more basal insulin is needed during the early morning hours, and less in the middle of the day. Daytime doses of intermediate-acting insulin, such as NPH, peak in the middle of the day or too early at night and increase the risk for hypoglycemia at these times.
Mealtime insulin should match your typical blood glucose rise caused by dietary carbohydrate. Most starchy and sugary foods cause a rapid blood glucose rise, with a peak occurring about an hour after eating. Rapid-acting insulin analogs do a nice job of covering the rapid blood glucose rise and then dissipating before they can cause hypoglycemia later on. Regular insulin tends to peak too late and last too long, increasing the risk of hypoglycemia several hours after eating.
For those taking pancreas-stimulating oral medicines, be aware that some — glimepiride, glipizide, glyburide, chlorpropamide, tolazamide, and tolbutamide — work constantly (whether you are eating or not), while others — nateglinide and repaglinide — work for a short time (just after eating). Obviously, nateglinide and repaglinide are less likely to cause between-meal lows.
2. Set an appropriate target.
Work with your doctor to determine an ideal premeal blood glucose level. This is the level that you aim for when making your mealtime dosing decisions. For most people with diabetes who take insulin, this is usually 100, 120, or 140 mg/dl. A target below 100 mg/dl does not leave much margin for error and may result in a greater frequency of low blood glucose. For those with Type 2 diabetes who use oral medicines, targets of 80, 100, or 120 mg/dl are common.
3. Take a look at your schedule.
Are you eating at the times your insulin or medicine is working its hardest? For those using an insulin pump, this is not generally an issue as long as the basal rates are set properly. For those using a long-acting basal insulin, there may be a tendency for the blood glucose to drop gradually during the daytime, so it will be necessary to eat at regular intervals. For those using daytime NPH or Lente, meal timing is a major issue: These insulins begin to work hard approximately four hours after injection, so carbohydrates must be consumed in specific amounts at specific times. For those taking sulfonylureas (glimepiride, glipizide, glyburide, chlorpropamide, tolazamide, and tolbutamide), it is not a good idea to skip or delay meals since the medicine is stimulating extra insulin production throughout the day and night.
4. Use caution when “covering” high blood glucose.
Each unit of insulin will cause the blood glucose to drop by a certain amount, but the amount may vary by time of day. For many people, each unit lowers the blood glucose more at nighttime than during the day. Make sure your “correction” doses take this into account.
Also, be certain to account for “unused” insulin (the amount that is still active from the previous dose). With rapid-acting insulin analogs, it usually takes about 3–5 hours for the insulin’s activity to fade completely. Regular insulin takes about 5–6 hours. A blood glucose reading taken 2 hours after a meal can be misleading since the insulin still packs a good deal of punch and the blood glucose should continue to drop. (See “Accounting for Unused Insulin” for guidelines on how to take still-active insulin into account.)
For those who take daytime intermediate-acting insulin, it can be difficult and dangerous to correct for high blood glucose until the intermediate-acting insulin has worn off. NPH insulin does not always get absorbed or act in a predictable manner. In general, to avoid hypoglycemia, it is best to wait at least 10 hours after taking NPH before correcting for high readings.
5. Adjust doses based on carbohydrate intake.
Of everything you eat, carbohydrate has the most profound influence on blood glucose levels. Virtually all forms of carbohydrate convert into blood glucose fairly rapidly. If your carbohydrate intake varies, your insulin and medicine doses should vary as well.
Carbohydrate also acts differently throughout the day. Most people need different doses of insulin or oral medicine to cover their carbohydrate at different meals. This is caused by varying levels of stress, insulin sensitivity, and physical activity throughout the day.
And if you’re going to go to the trouble of matching your doses to your carbohydrate intake, be sure that your carbohydrate counts are reasonably accurate. Look up the exact carbohydrate count for foods you are unfamiliar with. (An excellent resource for looking up carbohydrate counts is The Doctor’s Pocket Calorie, Fat and Carb Counter, which is available through your local bookstore or online.) Measure your portions. And don’t forget to deduct all of the fiber grams and half of the sugar alcohols from the total carbohydrate count; fiber is a carbohydrate that is not digested, and sugar alcohols only raise the blood glucose about half as much as an equivalent amount of ordinary carbohydrate.
6. Extend or delay your mealtime insulin when necessary.
Not all foods are digested at the same rate, so in some instances you will need to prolong your insulin’s action to prevent hypoglycemia after eating. For example, foods with a low glycemic index value (such as pasta, beans, and dairy products) usually take several hours to digest. With these kinds of foods, it might take 2–4 hours to see a significant blood glucose rise. (The glycemic index is a system of rating carbohydrate-containing foods based on how quickly they are absorbed; a food with a high glycemic index raises blood glucose levels faster than foods with a lower glycemic index.) If you were to take your full dose of rapid-acting insulin with your meal, the insulin would peak long before the blood glucose rises, resulting in hypoglycemia. To add insult to injury, your blood glucose may rise significantly several hours later once the mealtime insulin stops working and the food finally kicks in.
It is advisable to extend or delay your insulin when consuming food for a prolonged time, such as at a holiday meal or when eating a bucket of popcorn at the movies. Very large food portions also take a long time to digest. Think of your stomach as an hourglass and the food as sand trickling through. A very large portion of food, especially with a high fat content, might take several hours to pour through the stomach and into the intestines where it can be absorbed into the bloodstream, while a small portion will pour through relatively quickly.
In addition, a person who has gastroparesis (a nerve condition that causes the stomach to empty more slowly than usual) would also benefit from extending or delaying his mealtime insulin.
Extending or delaying insulin delivery can be accomplished in a number of ways. People who use mealtime rapid-acting insulin can take it 15–30 minutes after eating instead of before or during the meal. The dose could also be split into two injections — taking 50% with the meal and taking the other 50% an hour or two later. Alternatively, Regular insulin can be used instead of rapid-acting insulin when a slow-digesting meal is consumed.
For those who use an insulin pump, there are several options for prolonging or delaying the action of the mealtime bolus. Almost all pumps allow the bolus to be delivered over an hour or more (using the Square Wave or Extended boluses feature). Some allow a portion of the bolus, such as 33%, to be delivered immediately while delivering the remainder over the next couple of hours (Dual Wave or Combination boluses).
7. Adjust for physical activity.
With the exception of short bursts of high-intensity exercise, physical activity of almost any kind will lower blood glucose levels by accelerating the uptake of glucose by muscle cells. Note the term physical activity and not exercise. Physical activity includes exercises such as jogging, sports participation, and almost any form of physical conditioning. It also includes occupational activities and chores such as cleaning, shopping, yardwork, and home or auto repair. Recreational activities such as golf, gardening — and yes, even sex — count, too.
Work with your health-care provider to develop a plan to reduce your insulin or oral medicine when physical activity is anticipated. There is no way to tell exactly how much the activity will lower your blood glucose, so you might start out by reducing your dose by 33% when activity is planned within 90 minutes of the meal. For more intense activity, a 50% (or greater) reduction can be made; for less intense activity, a 20% or 25% reduction may be sufficient.
For activity that will take place before or between meals, it makes more sense to check your blood glucose and have a snack before you exercise. Again, the size of the snack depends on many variables, including your body size, the nature of the activity, and the timing and amount of your last dose of insulin or oral medicine. As a general rule, people who weigh 100 pounds will need approximately 15–25 grams of carbohydrate per hour of activity to keep their blood glucose steady. Those who weigh 150 pounds will need 20–30 grams; 200 pounds: 25–35 grams; 250 pounds: 30–40 grams, and so on.
Don’t forget that physical activity that is very intense and prolonged can produce a blood glucose drop several hours later. This is called “delayed-onset hypoglycemia.” Many people find that their blood glucose drops during the night following heavy daytime exercise, or in the morning following heavy exercise the night before.
Check your blood glucose more often than usual for up to 24 hours following heavy exercise. If you detect a pattern of delayed-onset hypoglycemia, you can prevent it by consuming extra carbohydrate or by lowering your insulin or oral medicine at the appropriate time. For example, to prevent the late-morning drops following nighttime exercise, try lowering your insulin dose at breakfast by 33%.
8. Be aware of alcohol’s effects.
While many alcoholic drinks contain carbohydrate that raises blood glucose levels fairly quickly, the alcohol itself has a tendency to make blood glucose drop several hours later. This is because alcohol inhibits the liver’s secretion of glucose into the bloodstream. When the liver is releasing less glucose than usual, the blood glucose level may drop.
After drinking alcohol, it is recommended that you reduce your insulin or diabetes medicine dose or consume extra carbohydrate. People who use insulin pumps can lower their basal insulin by 40% to 50% for approximately two hours for every drink consumed. Those who take NPH at night can lower their dose by a similar percentage after drinking. If you choose to eat to offset alcohol’s blood-glucose-lowering effects, choose a food that will take time to affect blood glucose levels such as ice cream, peanut butter, or yogurt. Fifteen to thirty grams of carbohydrate at bedtime should serve as a good starting point.
9. Check often.
Managing blood glucose is a lot like driving a car. If you pay attention and keep your hands on the wheel, you’re not likely to veer off the road. Close your eyes or let go of the wheel for too long and you’ll probably wind up in a ditch. Likewise, the more often you check your blood glucose, the less likely you are to suffer from extreme highs and lows. Checking before breakfast, lunch, dinner, and bedtime on a consistent basis, whether or not you take insulin or medicine at those times, will allow you to catch potential problems before they become too serious. A blood glucose level of 75 mg/dl at lunchtime should alert you to the need to either reduce your insulin or medicine or have some extra carbohydrate. Without knowing this, you could easily wind up hypoglycemic in the afternoon.
10. If it’s broke, fix it.
Take a good look at your blood glucose monitoring logbook every couple of weeks. If you see too many lows at a particular time of day, do something about it! Don’t keep doing the same things over and over, expecting different results. Perhaps you need to reduce or change your medicine. Maybe your insulin-to-carbohydrate ratio at a particular meal needs to be adjusted. Or maybe you just need to eat more carbohydrate when you are active.
As the saying goes, the one constant in life is change. The same goes for your diabetes self-care. What worked yesterday may not work today, so don’t hesitate to make changes if you see a pattern of low readings. A single low could be caused by just about anything, but a pattern of lows indicates a problem with your current program.
Living with diabetes can be a real pain in the rear sometimes (no pun intended). And nothing makes diabetes more disruptive in daily life than low blood glucose. Take the lows seriously. They present a greater threat to your well-being than any single high reading. While it may not be possible to eliminate the lows entirely, the 10 strategies listed here should allow you to lessen their frequency and severity.
It may not be possible or practical to implement all 10 strategies at once, so take them one at a time. Try focusing on one each week, and then add another the next week. If in 10 weeks you’re not completely satisfied, you can give me a call or send an e-mail. Maybe we can figure it out together.
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