Many people think of their blood glucose meters as a sort of sophisticated electronic toy. But the numbers they display after you check your blood really are meaningful.

In the United States, those numbers are a measure of how much glucose is in your blood expressed in milligrams per deciliter (mg/dl). A normal fasting level is below 100 mg/dl. The rest of the world measures blood glucose in millimoles per liter (mmol/l).

To convert mg/dl to mmol/l, divide by 18.

If you dislike pricking your finger to get a drop of blood for the meter, you might consider how we checked our levels before blood glucose meters were invented. Checking urine isn’t nearly as accurate; it’s also somewhat inconvenient and unpleasant and has to be done in private. Your meter really proves its value when you undergo personal changes, such as changes in your physical health, stress level or amount of exercise.

And now, our top 10 reasons your meter is your friend:
10. If you think that your blood glucose may be too low, your meter will be glad to check it for you. If the number is 70 mg/dl or less, you have low blood glucose. You will usually—but not always—have some symptoms. If your number is low, you need to treat it right away by taking glucose tablets or eating some fast-acting carbohydrates.

9. You may not even suspect that your blood glucose is too high until your meter tells you. In the short term you might or might not have symptoms. The long-term results of high blood glucose are any number of diabetes complications. Exercise (or fast-acting insulin, when indicated) will quickly bring down your level. But people with type 1 diabetes should avoid exercise if their fasting glucose levels are more than 250 mg/dl and ketones are present (measured by a urine ketone test or a blood ketone test with one type of meter, the Precision Xtra), or if their glucose levels are over 300 in any case, according to the American Diabetes Association Clinical Practice Recommendations.

8. Your meter will be glad to give you an education in how meals, physical activity and medicine affect your blood glucose level.

7. If you have a job in which poor control could cause safety problems, your meter is a friend who can document how well your blood glucose is controlled.

6. Your meter is your designated tester. It will help you decide if it is safe to drive or perform other tasks that require concentration if you are taking insulin or have had low blood glucose.

5. If you change your diabetes or other medicine, your diet, exercise routine or activity level, your meter is ready on a moment’s notice to report back to you.

4. If your level of stress increases, you can ask your meter for biofeedback on your blood glucose level.

3. If you are sick, your blood glucose level might go way up. But only your meter knows for sure.

2. Your meter can even help you socially. If you are at a dinner party and are served a food that you really dislike, you can test and then exclaim, “Oh, I guess I can’t eat that!”

1. If you are nervous, your friendly meter will give you something to do with your fingers.