What is a Normal Fasting Blood Sugar?

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  • Written By: Erin J. Hill
  • Edited By: Bronwyn Harris
  • Last Modified Date: 25 June 2019
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Most health care professionals consider a normal fasting blood sugar level to be anywhere between 70 and 99 mg/dL. Fasting generally refers to the period of time between eating dinner at night and waking up for breakfast the next morning. Glucose levels should be lowest during this period, but should be no lower than 70mg/dL. If it has not been at least four hours since food was last consumed, levels may be slightly higher than normal. Blood sugar readings lower than normal mean that it may have been too long since food was last consumed.

It is important to maintain normal fasting blood sugar, and checking one’s levels is a good idea to determine if pre-diabetes or diabetes has become a threat. Levels at or above 100 mg/dL indicate pre-diabetes, and levels above 125 mg/dL indicate full-blown Type 2 diabetes. Sometimes readings can be inaccurate due to taking the test incorrectly or not waiting long enough after eating to test. For this reason, additional testing should be performed everyday for at least three days to determine if levels remain high.


Low blood sugar is as big a problem as high blood sugar. Anyone with readings below the normal fasting blood sugar levels should be checked by a doctor if they continue for a week or more. Any level at or below 40 mg/dL should be investigated further. Type 1 diabetes is caused by the body not producing enough insulin, and treatment is necessary to avoid serious health complications.

For the most accurate readings, patients should check for a normal fasting blood sugar level by visiting a doctor and having their blood sugarchecked there. Those who are believed to be diabetic will be instructed to check their blood sugar levels at set intervals, depending on the severity of the case. Most times levels will need to be checked very frequently at first, and more time may pass between testing once blood glucose levels have been stabilized with diet, exercise, and sometimes medication.

Common treatments for high blood sugar levels are dietary changes and exercise. Low blood sugar levels may require insulin injections so that the body can break down glucose more effectively. With proper diet, sometimes pre-diabetes can be reversed and the disease may never materialize. This will depend on the individual patient and how well he or she monitors blood sugar over time. Eating well and maintaining healthy sugar levels must be done over the duration of one’s life.



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Post 2

@ElizaBennett - According to WebMD, the fasting blood sugar test is usually the first test done when someone who is *not* pregnant is suspected of having diabetes or prediabetes.

On the other hand, the syrup test (or glucose tolerance test) is the typical test for pregnant women. What I don't know is why a different test would be preferred for pregnant women. The GTT test is apparently never (or almost never) used in people who are not pregnant. Maybe GD and "regular" diabetes are quite different?

Post 1

When I was pregnant, I had a fasting blood glucose test instead of the drink-the-syrup test, whatever that is.

I wasn't really comfortable with drinking the syrup; it doesn't seem to be a very useful test in women who do not have other signs of gestational diabetes (and there are almost always signs). And I just didn't like the idea of dumping all that sugar into my body when I try so hard *not* to eat much sugar!

My midwife suggested the fasting blood glucose test as an alternative. I just went in first thing in the morning before breakfast.

I'm not sure if that test was any more useful, but at least it was non-invasive!

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