Blood Sugar Too High? Blood Sugar Too Low?

What Your Blood Sugar Readings Might Mean
All Rights Reserved

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

about 1 month, said...

hi, my blood sugars keep lowering at night, i actually went into a coma one night and almost died. what should i eat at dinner and i do take insulin

about 2 months, said...

is 192 mg/dl to high for type 2 diabetes right after last meal and ice tea

7 months, said...

Hello I have been to the doctor, and been tested for AC1 the doctor says pre diabetes, however I have been told I do have it, and no medication has been given. I have been doing some research, and my provider says yes I do have it, and wanted to know why my doctor has not given me anything for it. It has not been under 140, every day, and has averaged 140 even for 7 days. it stays that way or higher. yet even when I go to re search it still confirms what my provider says. what should I do to get my doctor to be serious about this? I am so tired all the time, and I try to do what I can. Is there anything I can do about this? I have had the A1c test, and it still said I am pre diabetes, and probably have it. what can I do????? any ideas?????

10 months, said...


over 1 year, said...

What is to high blood sugar level? One number may be to high for one person and ok for another person! No one seem to be able to give that info to me. When does damage acure at what high numbers? My numbers ranges anywhere from 125-280 even if I watch my eating very carefully it doesn't seem to matter my numbers will appear high no matter what I do. i am on insulin with the lantus pen 54 units a day and glimepiride 2mg a day. My a1c is 7.7 and Im 74 years old and had diabetes 2 for 18 years. Thanks my friends for and insight you can give me have a wonderful day!

over 2 years, said...

My blood test.. fasting.. results came too high they said that my glucose was 97mg is that too high ?? for a 27 year old female /5.5H/ 205 lb

over 2 years, said...

my blood sugar has'nt been over 155 in the last five months. I havent taken insliun in months. what causes this?

almost 3 years, said...

My wife sugar of blood

about 3 years, said...

always had problems with blood sugars ranging from 80 to 240 . I have had two heArt attacks thi past year they put in 4 stents. I am chasing my blood sugars which is making me nervous because I'm shooting insulin a lot ( humolog ) to keep sugers under 200, my range or goal where I feel goodis 150 to 180 anything under 120 I feel pins and needles and nervous I guess I'm not used to normal counts do you thing 150 to 180 is a safe range

almost 4 years, said...

Fasting and 103 glucose age 63. Is this diabetics

over 4 years, said...

my blood sugar levels are rising alot here is a three day reading one per day at random times during the day. what should i do????? sat. 208 at 3:30pm sun. 218 at 10:30am mon. 179 at 12:30pm. any info is helpfull and appreciated.

almost 5 years, said...

My husband levels are high all the time. Over 120 eating or not. As high ad 500.

almost 5 years, said...

It is a very good article about the diabetes melites. tell us more about symptoms and the treatment and prevention.

almost 5 years, said...

This is positive. Keep up the good work.

about 5 years, said...

what the blood levels are/what they should be as normal.

about 5 years, said...

I like the good descriptions and the ranges given. Thank you!

about 5 years, said...

Verygood article