Blood Sugar Too High? Blood Sugar Too Low?

What Your Blood Sugar Readings Might Mean
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If you have diabetes, your blood sugar doesn't call your cell phone and say, "My readings are too high right now." Instead, blood sugar rises slowly and gradually, causing complications that may damage your organs -- heart, eyes, kidneys, nerves, feet, and even skin are at risk.

Sometimes you wonder, "Is my blood sugar too high? Too low?" because "normal" levels are so important.

"Diabetes is not a 'one-size-fits-all' condition, and neither are blood sugar readings. Different targets are established for different populations," says Amber Taylor, M.D., director of the Diabetes Center at Mercy Medical Center in Baltimore, Maryland.

Targets may vary depending on a person's age, whether they have type 1 or type 2 diabetes and for how long, what medications they're taking, whether they have complications, and, if the patient is a female, whether she is pregnant.

"Patients on insulin may need to test more frequently than someone on oral agents," says Taylor. "Those with type 1 diabetes always require insulin, but many with type 2 diabetes also need it."

Target Blood Sugar Levels

If you have diabetes, these are target "control" blood glucose levels, using a rating of milligrams to deciliter, or mg/dl:

  • Blood sugar levels before meals (preprandial): 70 to 130 mg/dL

  • Blood sugar levels one to two hours after the start of a meal (postprandial): less than 180 mg/dL

  • Blood sugar levels indicating hypoglycemia or low blood glucose: 70 or below mg/dL

Types of Blood Sugar Tests

Blood glucose testing can screen, diagnose, and monitor. Glucose is measured either after fasting for eight to ten hours, at a random time, following a meal (postprandial), or as part of an oral glucose challenge or tolerance test.

You can compare your levels to these results for specific tests, based on clinical practice recommendations of the American Diabetes Association (ADA):

Fasting Blood Glucose Test Levels

  • Blood sugar levels from 70 to 99 mg/dL indicate normal fasting glucose.

  • Blood sugar levels from 100 to 125 mg/dL indicate impaired fasting glucose, or prediabetes.

  • Blood sugar levels 126 mg/dL and above on more than one testing occasion indicate diabetes.

Oral Glucose Tolerance Test Levels

(Blood drawn two hours after patient drinks 75 ounces of glucose drink.)

  • Blood sugar levels less than 140 mg/dL indicate normal glucose tolerance.

  • Blood sugar levels from 140 to 200 mg/dL indicate impaired glucose tolerance (prediabetes).

  • Blood sugar levels over 200 mg/dL on more than one testing occasion indicate diabetes.

Random Glucose Tests

Self-testing, done at a random time, is used to monitor diabetes, usually with a glucometer. "You don't need a prescription, and insurance usually covers test strips," Taylor says. "If you're using insulin, do it three to four times per day -- after fasting, before meals, at bedtime, and sometimes after meals."

The National Institutes of Health say that if you had a random blood glucose test, normal results depend on when you last ate. Most of the time:

  • Blood glucose levels will be below 125 mg/dL.

  • Levels of 200 mg/dL typically mean diabetes, and if you have diabetes, they may mean the diabetes is not well controlled.

If so, your healthcare provider will likely order a fasting blood glucose or a glucose tolerance test, depending on your random test result.

A1c Test

The hemoglobin A1c, or glycosylated hemoglobin, screens and provides a reliable marker of a three-month average blood sugar range without daily fluctuations -- it doesn't replace daily self-testing, says Gregory Dodell, M.D., an endocrinologist and diabetes and nutrition specialist in private practice in New York City and on the teaching staff at St. Luke's-Roosevelt Hospital Center.

"This test actually marks how much glucose is on the red blood cells or hemoglobin," Dodell says. "It's less cumbersome -- it doesn't matter what time of day we test, since no fasting is required."

For A1c, the ADA recommends:

  • A target blood sugar level of 7 percent.

What to Do if Your Blood Sugar Is Too High or Too Low

"The diagnosis of diabetes requires a new commitment to make lifestyle changes, many of which may be very difficult, but which will help ensure the prevention of diabetes-related complications," says Dodell.

"There are no 'good' or 'bad' blood sugars, but each value should give us more information about what is happening in the body," Taylor says. "If blood sugars run high or low, we need to make adjustments to the diabetes treatment regimen. Ultimately it doesn't matter how we get blood sugars to their target -- whether it is weight loss, exercise, oral medications, or insulin -- the numbers matter most."

Monitoring your blood glucose levels is a way to track how well your diabetes care plan is working -- but it's no reflection on you. It may indicate your diabetes plan needs changing. Keep a log to track levels, then share with your healthcare provider.

Remember: Severe stress like trauma, stroke, or heart attack might cause blood glucose levels to rise temporarily. Certain drugs can increase glucose measurements, including beta-blockers, corticosteroids, estrogens, and tricyclic antidepressants. Conversely, some substances can decrease measurements, like acetaminophen, alcohol, and monoamine oxidase inhibitors (MAOIs).

Stephanie Stephens

Stephanie Stephens has a Masters degree in journalism but had no degree in caregiving -- desperately needed when her mother was diagnosed with Alzheimer's disease. See full bio