American Diabetes Association Complete Guide to Diabetes: The Ultimate Home Reference from the Diabetes Experts


Basics of Blood Glucose Monitoring

• Who Should Monitor?

• How Often You Should Monitor

• When to Do Extra Checks

Monitoring your blood glucose is an important tool for taking care of yourself and your diabetes. Your health care provider will perform tests to measure your average blood glucose level at most visits, as discussed in more detail in chapter 2. However, the blood glucose monitoring that you do every day—on your own—will form the backbone of your diabetes management plan.

Blood glucose readings help you understand how you respond to different situatixons: food, exercise, illness, and even stress. Readings also help you make informed choices for treating your blood glucose with insulin or other medications, food choices, and physical activity. Ultimately, these choices help you feel better each day and prevent complications down the road.

This chapter will explain some of the basic guidelines for monitoring blood glucose, such as who should monitor, how often you should monitor, and when to do extra checks. Keep in mind that blood glucose monitoring is up to you. You will be the person most responsible for keeping tabs on your diabetes and making adjustments to fit your lifestyle and health goals.

Who Should Monitor?

The simple answer is . . . you.

People with diabetes who take insulin should always monitor their blood glucose. People with type 2 diabetes who take diabetes pills should check with their health care providers about whether and how often to monitor. Insulin and other diabetes medications are powerful drugs that lower blood glucose. You can tell how well they are doing their job by keeping track of your blood glucose. Also, when you use these medications, you are at risk for low blood glucose (hypoglycemia). Monitoring will tell you if your blood glucose is low, so that you don’t have to guess. It can also guide you in deciding how much and which foods to eat at meals.

People with type 2 or gestational diabetes who manage their blood glucose with exercise and meal plans do not need to worry as much about low blood glucose levels. However, monitoring may be helpful. It gives you feedback on how well your diabetes care is working. Positive feedback may be a wonderful source of encouragement for you. You can see the effects of your exercise program or food choices. For pregnant women, it guides the treatment adjustments that will help keep you and your baby healthy.

The best way to lead a healthy life is to take charge of your diabetes. You can do this by managing glucose levels with food, physical activity, and medication. The single most important thing you can do for yourself is to keep track of the amount of glucose in your blood on a regular basis.

Monitoring is the only way to know how your body responds to food, medication, activity, and stress. Without knowing this, you can’t make changes in your diabetes care plan. Trial and error—and a little patience—will help you reach your glucose goals.

Instead of saying “I feel good” or “I feel terrible,” take measurements and keep records. These records will tell you how well your diabetes plan is working.

Why Should I Bother?

• If you take insulin or certain diabetes pills and your blood glucose level swings too low over the course of the day, you could develop hypoglycemia. For example, if you take insulin and your blood glucose level drops too low and you don’t treat it, you could fall unconscious.

• High blood sugar may not cause an immediate emergency but may lead to severe complications over time. People with a history of chronic high blood glucose can develop debilitating eye disease, kidney disease, circulation problems, or nerve disease. They can also be at risk for dehydration.

How Often You Should Monitor

Of course, how often you monitor your blood glucose is highly individual. It depends on: whether you have type 1 or type 2 diabetes, your blood glucose goals, how often you’re willing to prick your finger, and what supplies you can afford. How often you monitor also depends on your reasons for checking your blood glucose.

If you have type 1 or type 2 diabetes and you use the results to adjust your next insulin injection or food intake, then you may need to check your blood glucose level each time before you inject or eat a meal (3–4 times a day). You might also monitor after meals to see if you gave the right insulin dose.

If you aim for a blood glucose level close to normal, it’s essential to monitor at least four, and sometimes eight, times a day. You would check before and after each meal and before bedtime every day and in the middle of the night (around 3 a.m.) about once a week. Studies in type 1 diabetes have shown a relationship between the number of blood checks a day and blood glucose control. You’ll hear more about setting goals for keeping your blood glucose levels as close to normal in chapter 9.

However, you may only be taking one or two insulin shots each day or oral medications, so you may decide to monitor just two times each day. Blood glucose levels in people with type 2 diabetes are often more stable over the course of a day. If you take oral diabetes medications, you may not need to monitor as often because you can’t use the results to fine-tune your dose.

People with type 2 diabetes who manage their blood glucose without medications might monitor once or twice a day, three or four times a week, or not at all. However, checking your blood glucose levels regularly will help you keep track of your diabetes and see how all of your efforts are working. One approach is to routinely measure your fasting or pre-breakfast blood glucose levels. It can also help to check your blood glucose at different times of the day: before and after exercise, before and after meals, and at bedtime. This gives you a better idea of what is happening with your blood glucose levels.

Monitoring Goals

Your goal is to understand the pattern of your blood glucose in response to your daily lifestyle. However, you may also need to capture unusual highs and lows.

Standard Times to Check Blood Glucose

• Before breakfast, lunch, dinner, or an especially big snack

• Before you go to bed

• 1–2 hours after breakfast, lunch, dinner, or an especially big snack

• At 2 or 3 a.m.

Sometimes you may not feel quite right, and you may not know why. Monitoring your blood glucose may help you pinpoint the problem. For example, if you feel sweaty and a little shaky after a three-mile run, you may just be tired from the workout or you could be having a low blood glucose reaction. You simply don’t know without monitoring. You may decide to eat because you think your blood glucose is low, but it could actually be high. Only monitoring will give you the information you need to make the right decision about treatment.

Over time, you will gain confidence in your ability to manage your diabetes. You may think it’s okay to monitor less often. Beware! It’s tempting to think you can tell what your glucose level is by the way you feel, but research shows that most people cannot guess their glucose levels reliably. Guessing is dangerous, especially if your blood glucose level tends to swing with little warning.

When to Do Extra Checks

There are times when you’ll need to monitor your blood glucose more often, particularly when you’re trying to decipher how new situations affect your blood glucose. In general, changes in medication, food, physical activity, stress, and illness will affect your blood glucose. So, you’ll need to perform extra blood glucose checks during these situations. These checks will help you respond to and treat your blood glucose properly. Remember, you should always monitor your blood glucose when you suspect that it is too high or too low.

Extra Checks for Meals

Put most simply, some foods make your blood glucose go up. However, there are quite a few nuances to keep in mind. The amount and type of carbohydrates in certain foods, as well as the amount of food you eat during a meal, will affect your blood glucose level. Sounds complicated, right?

Well, the best way to take charge is to begin to learn how the food you eat affects your blood glucose levels. You’ll want to monitor your blood glucose more closely when you eat new foods or eat special meals. You may be surprised at how your glucose level responds to different foods. Measure your blood glucose 1–2 hours after you eat particular foods. Do you find that your blood glucose rises faster after you eat rice or pasta? Does it rise faster after a cookie or a granola bar? By figuring out how your body responds to specific foods, you can have a plan so that your blood glucose will not rise too high, too fast. You can read more about managing your diabetes and food in chapter 10.

Extra Checks for Physical Activity and Exercise

In general, physical activity, including exercise, will lower your glucose and make your body more sensitive to insulin. During exercise, your muscles work harder and use up the glucose they have stored for fuel. Your body uses glucose from the blood when the glucose stored in muscles becomes low. Exercise can help use up some of the glucose that builds up in the blood.

You need to take special precautions when you exercise. You want to make sure that your blood glucose levels don’t drop too low too fast. This can happen in the hours after exercise when your muscles take glucose from the blood to restore their glucose reserves (this is more common in type 1 diabetes). Make sure to check your blood glucose immediately after exercising as well as several hours later.

Doing extra checks before and after physical activity will help you decide if you need to eat a little more or inject a little less insulin. Some people with type 2 diabetes find that they no longer have to take insulin or other diabetes medications once they start a regular exercise program. However, to be safe, talk over your blood glucose readings and exercise program with your health care team before you make changes to your diet, insulin, or other medications. Read more about managing your diabetes and physical activity in chapter 11.

High Blood Glucose and Exercise

It sounds strange, but people with type 1 diabetes will also need to check their blood glucose to make sure that it isn’t too high during exercise. If your blood glucose level is over 250 mg/dl, exercise may cause your blood glucose level to go up rather than down.

Hard exercise with too little insulin can make the liver release stored glucose. Someone with type 1 diabetes whose blood glucose is greater than 250 mg/dl should test for ketones (read about how to test for ketones in chapter 7). Do not exercise if ketones are present. Use caution if your blood glucose is greater than 300 mg/dl, even if no ketones are present.

Extra Checks for New Medications or Insulin

If you have type 2 diabetes and take oral medication, finding the best dose can be tricky. You will need to monitor frequently when you are starting a new medication or trying to find the best dose of medication. Check your blood glucose once or twice a day (before breakfast and one other time during the day) to avoid low blood glucose. Occasionally you may want to check 2 hours after meals to see how well the medication works with your meal plan. Your monitoring records will help you and your health care provider decide what changes, if any, are needed.

Starting or changing an insulin plan will also mean more blood glucose monitoring. Read up on the specifics of insulin in chapter 13.

Other Times for Extra Checks

• Before you drive (if you take insulin)

• When you are more physically active than usual

• When you have lost or gained weight

• If you start taking a medication for another condition that affects blood glucose levels or your ability to recognize low blood glucose warning signs

• If you have hypoglycemia at night or wake up with high blood glucose levels

• When your levels have been outside your target range more often than in your range

• If you don’t feel well. Checking helps you determine whether your glucose level needs attention

• If you’re pregnant

Extra Checks during Stress

Everyone seems a little stressed out these days—and living with diabetes can add even more stress to your life. Stress can produce hormones that raise blood glucose levels. Stress can also be a hidden contributor to unexpected swings in blood glucose levels.

Therefore, you’ll want to check your blood glucose more often when you’re experiencing stress. The effects of stress on your blood glucose can’t be measured as easily as units of insulin or calories burned during exercise. However, stressful situations could be throwing your blood glucose out of range (for example, if you have a bad day at work), so make sure to check your blood glucose when you feel stressed.

When you can’t figure out why your blood glucose level is so high despite “doing everything right,” think about the stresses in your life and how you respond to them. Do you eat when you are under stress? These extra calories, plus stress hormones, could raise your blood glucose.

Extra Checks during Illness

Being sick is another kind of stress on your body that can raise blood glucose. Your body releases hormones to fight the illness, but these hormones also counteract the effect of insulin and raise blood glucose. Sickness can cause your diabetes to go out of control. Extremely high blood glucose levels caused by illness can also lead to diabetes emergencies, including coma and death.

Blood glucose monitoring is especially important during any illness. Even if you have type 2 diabetes and only monitor once a day, you may want to check more often during times of illness. In general, you’ll want to check your blood glucose every 3–4 hours. Read more about handling sickness under the “Illness” section in chapter 8.

Tips on Using Results of Self-Monitoring

Throughout the book, you’ll find more advice about using the results of self-monitoring. Your results will help you develop your diabetes management plan, including your goals for meals, physical activity, and treatment.

Sometimes, you’ll need to take immediate action based on a blood glucose reading, while many other times you’ll use the information to interpret a pattern and make future adjustments. This is particularly true for people who are not taking multiple, daily injections of insulin.

Self-monitoring is also important for identifying blood glucose emergencies. Chapter 8 will describe some common blood glucose emergencies and how to handle them.

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