Checking Your Blood Sugar

If you have diabetes, a single drop of blood can speak volumes. When placed on a test strip and fed into a blood sugar meter, that little drop can tell you whether, at that moment, your sugar level is too high, too low, or just about right.

You can also get an important glimpse into the future. If your blood sugar is too high for too long, you could be at risk for long-term complications such as blindness, heart disease, and amputations. By testing your blood sugar regularly, you can track the effectiveness of your medication, make informed decisions about meals and exercise, and head off problems such as high blood sugar or low blood sugar (hypoglycemia) before it's too late.

Checking blood sugar is an easy process, but it's possible to go astray. If you skip tests, don't record the information properly, or misuse the meter, your sugar levels could still be a mystery. Your doctor or diabetes educator can help you avoid these traps. Be sure to ask plenty of questions, and don't stop until you feel ready to measure your sugar levels on your own. Different patients have different needs, but some basic tips apply to everyone.

When should I check my blood sugar?

Your diabetes educator or your doctor can help you set your schedule. According to the Joslin Diabetes Center, most patients on insulin have to check their blood sugar several times a day. You may also need to do daily monitoring if you are newly diagnosed with diabetes, if your blood sugar is not well-controlled, or if you're making major changes in your food intake or energy expenditure that could influence your blood sugar. If any of these applies to you, you may want to check your blood sugar once in the morning, an hour before each of the three major meals, and right before bedtime. Your doctor may also suggest checking two or more hours after meals to see how food affects your sugar levels.

No matter what time of day it is, you should check your sugar levels if you start feeling the symptoms of low blood sugar (such as sweating, shakiness, or dizziness). You may also need to start checking more often throughout the day if you have a sudden illness, if you're pregnant, or if there's been a change in your medicine or treatment. If you are not on insulin and doing well with your blood sugar, you may not need to check your levels more than once a week.

What type of meter should I use?

There are many types of meters on the market today: You're bound to be able to find one that works well for you. You may need to get a meter for your specific needs, and your doctor or diabetes educator may recommend a particular brand. If you have trouble reading small numbers, for example, you'll need a meter with a large display. If you want to avoid a little record-keeping, you can pay extra for a meter that records and stores your numbers, or one that can download your records into a computer.

Unlike older meters, the new versions are smaller and lighter, with carrying cases for lancets and strips; most meters come with the battery installed. You may decide you want one that does not require test strips, or the one that gives the fastest reading. Some meters deliver a reading immediately. Some are so easy to use that even children find them a snap, according to diabetes educators.

Cost may be the deciding factor. Some insurance plans will only cover certain types of meters, and often pay for only a limited number of test strips per month. Find out before you order.

If you use a meter that works with an insulin pump, select a brand that allow you to transfer your glucose data wirelessly from the meter to your pump. The insurance company should cover the cost of your meter because it works as part of the pump "unit." See this article from Diabetes Forecast magazine for more advice on what to look for in a meter: http://www.diabetesforecast.org/2015/mar-apr/meters-does-your-device-measure-up.html

How should I draw the blood?

There are several different devices for drawing blood, ranging from old-fashioned lancets to spring-loaded models. Depending on the meter you use, you may be able to draw blood from your forearm, thigh, or hand. These sites are convenient, but, according to the FDA, they may not be the best places to get an accurate reading of your blood sugar, especially if your sugar levels are changing rapidly.

Most patients draw blood from their fingertips. You can avoid some discomfort by poking the side of the fingertip, the part that doesn't get much use, or by testing on a hand that you use less often. To make it easiest to get the blood, wash your hand in warm water, shake it below your waist a few times, and squeeze your finger to pool blood near the tip. Use a fresh lancet for each stick. Make sure you cap the lancets and throw it and the test strips away as soon as they're used. That way they don't get mixed up with unused supplies.

How can I make sure the meter is accurate?

Have your doctor or diabetes educator show you how to use your meter before you take it home. Even a nurse or a physician's assistant at your doctor's office can give you a quick lesson. You should also know how to keep your meter clean. Some can be washed regularly with soap and water, while others must be cleaned by the manufacturer. Once a year, test yourself in front of your doctor or diabetes educator to make sure your technique is still sound.

Here are some other tips:

  • Make sure that your meter is set to the same number as the bottle of test strips you're using. Each bottle comes with a numbered code -- ask your diabetes educator what this means and how to test the meter's calibration. If it doesn't match, you could end up with a wrong reading.
  • Your meter is a machine, so make sure you don't drop it.
  • Check your booklet to make sure you know how to tell when the meter is not working correctly.
  • Even if you're very careful, your meter can make mistakes. If the number doesn't seem believable -- if, for instance, it's much higher than normal but you feel fine -- test yourself again.

How should I keep track of the readings?

Even if your meter automatically records your blood sugar levels, a diabetes calendar can be a helpful tool for your blood sugar control. Your diabetes educator can give you forms (or the URL for an online form) that allow you to record the time and date of each reading. You'll also have space to write down important information such as the medicine you took that day, your exercise, or your diet. Such records can uncover patterns in your blood sugar fluctuations and help fine-tune your treatment.

What do the numbers mean?

Your meter measures the total amount of sugar in your blood. The level is expressed as milligrams of glucose (sugar) per deciliter of blood (mg/dl). A person without diabetes would normally have a reading below 100 on an empty stomach and below 140 two hours after a meal. According to the American Diabetes Association, the basic goal for people with diabetes is a reading between 70 and 130 on an empty stomach and less than 180 two hours after the start of a meal. Your diabetes educator may set different targets for you. Don't be discouraged, for example, if your blood sugar levels are higher than you expect; work with your health care team to get those numbers down. Do call your doctor if your blood sugars are unusually high or low -- he or she will want to know about these changes and help you adjust your treatment program so that you stay out of trouble and reach your goals.

It's important to realize that most lab tests measure the amount of sugar in your plasma, not your whole blood. According to the FDA, plasma readings tend to be about 10 to 15 percent higher. Many meters automatically adjust their measurements to give you a "plasma blood glucose" reading. If your meter doesn't have this feature, you and your doctor will have to adjust your goals accordingly.

References

American Diabetes Association. Checking your blood glucose.

Joslin Diabetes Center. Blood glucose monitoring: Your tool for diabetes control.

U.S. Food and Drug Administration. Glucose meters and diabetes management.

American Academy of Family Physicians. Diabetes: Monitoring your blood sugar level.

Joslin Diabetes Center. Goals for blood sugar control.

American Diabetes Association. Hypoglycemia.

Children with Diabetes.com. Glucose Meters Overview.

American Diabetes Association. Diagnosis and Lab Tests. http://www.diabetes.org/type2/medical/lab/default.jsp

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