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Why, When & How to Test Your Blood Glucose

You have just returned home with your brand new blood glucose meter (BGM). You know how to use it, but what do you do with the numbers? You have been diagnosed with diabetes in one of three ways: your fasting blood glucose was greater than seven mmol/L, random blood glucose tests were greater than 11 mmol/L., or either a glucose or an oral glucose tolerance test was greater than 11 mmol/L. The numbers on the meter let you know how you are managing your diabetes. They warn you of developing danger when they drop too low or rise too high. These numbers can show how quickly a new medication begins to work. By testing after a meal, you can find out how your body is handling carbohydrates and other food in your diet.

A blood glucose number is a snapshot of a moment in time. The more you test, the more you will know about how your body is managing the diabetes. Imagine going on a holiday and only taking one picture. It is easy to forget the details of your trip.

Testing at various times during the day allows you to make more informed decisions. Most health professionals now recommend testing at least once a day if you have type 2 diabetes, and three times a day if you have type 1 diabetes. Recording the numbers, along with a list of your activities, diet, and how you feel, gives a larger picture of your diabetes management. Make sure you bring your logbook to all of your medical appointments.

What is the target range?

Your diabetes educator will mention target values that may seem hard to attain. Many studies have shown that keeping blood glucose within target ranges most of the time can delay or prevent complications of diabetes. Typically, the target for blood glucose when you have not eaten is four to seven mmol/L.

After you have eaten, your blood glucose number will ideally fall within another target range. For most people, that range lies between five and 10 mmol/L. Blood glucose peaks usually two hours after you eat. Those with type 1 diabetes, who must use insulin to manage their diabetes, should also strive for a blood glucose number between five and 10 mmol/L two hours after eating. By checking blood glucose both before you eat and two hours afterward, you can see whether your meal fits into the healthy target range. If your value after you eat is greater than 10 mmol/L, it is outside of the goal range. You may want to adjust the type or amount of food. The next time you eat that meal, alter the quantity of carbohydrate or combine it with a protein. Test your blood glucose again to see whether the number is in the target zone. The goal is to avoid a high or low in blood glucose while still feel satisfied after eating a meal.

These numbers may be different for young children and those who have heart disease, live alone, or are pregnant. Check with your diabetes educator or doctor to determine the right target levels for you.

If you take insulin, it is important to check your blood glucose level before bedtime. Half of low blood glucose reactions happen during the night. If your value is less than seven mmol/L at bedtime, consider a carbohydrate and protein snack. Check your blood glucose again if you wake during the night. Do another test first thing in the morning to see whether you are still in the target range.

Checking your blood glucose before you get behind the wheel is part of being a responsible driver. If you are taking insulin or medication to increase insulin production, your blood glucose may fall too low to allow you to think properly. The brain needs carbohydrate as a fuel source to make decisions. Test before you drive, and if your blood glucose is less than five mmol/L, have a carbohydrate snack. Always carry dextrose or other quick-acting products in your vehicle as first aid for low blood glucose.

Driving, especially if it is stressful, can lower your blood glucose. By testing to ensure that your blood glucose is within range, you can eliminate emergency situations while driving.

What happens if blood glucose is too low?

The brain is usually one of the first body organs to recognize low blood glucose (hypoglycemia). The body needs carbohydrates to fuel it. When blood glucose is mildly low, you may feel anxious or hungry. As the blood glucose level drops further, headaches, vision changes, dizziness, irritability and difficulty concentrating are symptoms. At this point you may need help in treating your low blood glucose. If it drops more, you can become drowsy, feel weak and even lose consciousness. Since your family members may be the first to notice that you are having a low blood glucose reaction, they must know how to help.

The only way to be sure of your blood glucose level is by testing blood from your fingertip. Although some meters offer alternate site testing on areas like the arm, the fingertip is the best place to test when you think you are having a low blood glucose reaction. Blood in the fingertip is the first to show glucose changes.

If your blood glucose measures less than four mmol/L, you must treat it by taking in 15 grams of fast-acting carbohydrate. You might use three glucose tablets, three-quarters of a cup of regular pop, or eight hard candies. Test again within 15 minutes. If it is still low, treat the symptoms again.

Treatment changes when blood glucose levels are severely low. If you are conscious and able to swallow, 20 grams of fast-acting carbohydrate should be given to you. For instance, four glucose tablets or four teaspoons of sugar or honey might be used.

If you are unconscious, someone must give you glucagon by injection and call 911. Your blood glucose must be rechecked in 15 minutes and treated if it is less than four mmol/L.

Once your blood glucose is safely above four, have the meal or snack you usually would at that time of day. If a meal is more than an hour away, eat a snack (with carbohydrates and protein) to sustain your blood glucose. If you experience severe or frequent low blood glucose reactions, your body loses its ability to recognize them (called hypoglycemia unawareness). The only way to prevent this lack of awareness is to prevent low blood glucose reactions.

What happens if blood glucose is too high?

If the insulin the body makes is not used appropriately, or not enough insulin is given, you will experience high blood glucose. The symptoms are recognizable – you may be very thirsty, very tired and have to urinate often. You must test to find out the range of your blood glucose levels.

When there is not enough insulin, the body breaks down fat and muscle as a fuel source. This releases ketones into the blood stream. Ketones alter the chemical balance in the body, which can make you even sicker, and ketoacidosis may develop. When your blood glucose is over 14 mmol/L, test for ketones.

With type 2 diabetes, high blood glucose numbers may mean that your current treatment is not working. Even a few days of nausea, vomiting or diarrhea can put your electrolytes and blood glucose severely outside normal ranges. In this case, medical help is necessary. Go to the doctor or hospital. For both types of diabetes, you need to have a sick plan before illness strikes. Talk to your doctor or diabetes educator to make a sick day plan so you know when to call for help. Blood and urine ketone testing strips are available at your local pharmacy.
If your blood glucose is consistently outside the target ranges, talk to your doctor about changing your medications. Those with type 2 diabetes may need insulin as their diabetes progresses. It can be used short-term during an illness or long-term to help control blood glucose levels.

Exercise

Everyone needs physical activity to keep our minds and bodies healthy. One benefit of physical activity is that it makes the body more sensitive to the effects of insulin. If you take insulin or medications to increase your body’s insulin production, you must test before you exercise to ensure that your blood glucose levels are safe.
Depending on the activity, you may need to eat some carbohydrates to keep your blood glucose levels above four mmol/L. The amount of carbohydrate you require depends on the type and intensity of the activity. If you feel the symptoms of low blood glucose while you exercise, check your glucose level and treat it if necessary.
Physical activity can lower blood glucose for up to 24 hours, so test often during the day or so after adding a new exercise to your routine.

Those with diabetes have many choices. A variety of meters are available for purchase. You can choose different foods or portions of foods to fit in your goal ranges. Testing with your meter gives you an idea of how your body is managing the food you have eaten. If you test before you drive, you will be a safer driver.
Testing your blood glucose to manage your diabetes can help you enjoy a healthier lifestyle and avoid the complications of diabetes. Check your blood glucose to take some snapshots of how you and your body are managing the lifelong condition called diabetes.