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What should the normal blood sugar be?

Updated on August 10, 2014

Average Blood Sugar Level

In the United States, blood sugar levels are measured in mg/dL. This is known as the glucose serum test and can be measured at the lab via a blood test or it can be measured using a $20 glucometer that you buy at your local drug store without a prescription. (Although the meter is inexpensive, the test strips may be more costly). However, the blood test at the lab may be more accurate than the glucometer which can sometime go off-calibration.

Average blood sugar should be around 70 to 100 mg/dL. It is okay for blood sugar to temporarily go above 100 (such as after a meal or when under stress) -- but not when it is chronically high.

Your doctor will often ask for a fasting blood sugar test where you would not have any food for 8 to 10 hours so that your "fasting blood sugar" was not affected by the food you ate.

DiabetesDaily writes ...

"In a person without diabetes, blood sugars tend to stay between 70 and 100 mg/dL (3.8 and 5.5 mmol). After a meal, blood sugars can rise up to 140 mg/dL or 7.8 mmol. It will typically fall back into the normal range within two hours."

Diabetes and pre-diabetes is when blood sugar level are chronically above normal levels.

In general, Type 2 diabetics have to worry about blood sugar getting too high. And Type 1 diabetics have to worry about blood sugar getting too low (especially during sleep in the middle of the night).

Low blood sugar or hypoglycemia is when blood sugar drops below 70 -- you don't want that either. Signs of low blood sugar during the middle of the night may include night sweats, nightmares, and headaches.

Normal level of Hemoglobin A1C

Another blood test for blood sugar is the Hemoglobin A1C test. This one you have to do via a lab. While the glucose blood test measure the sugar of the blood at the instance when the blood is drawn, the Hemoglobin A1C will give you an indication of your three month average of your blood sugar. Actually it measures what percent of your red blood cells have been glycated (damaged) by excessive sugar in the bloodstream.

So a Hemoglobin A1C of 6.0 means that 6% of your red blood cell have been damaged by excessive sugar. Red blood cells live about 3 months before they turn over and newly created blood cells take their place.

WebMD writes that normal Hemoglobin A1C is 4% and 5.6%.

5.7% to 6.4% is pre-diabetes. And 6.5% or higher is diabetes.

What should blood sugar be after a meal?

After eating, your blood sugar level should return back to baseline after 3 hours. If not, it may be that you ate too much carbohydrate for you sugar tolerance level for that meal. Diabetics have lower tolerance for sugar and hence need to eat a lower carb meal to keep blood sugar in check after a meal. Also doing movement (such as walking) after a meal will keep prevent blood sugar spikes after a meal.

Chris Kresser provides some more numbers as to what you blood sugar should be one hour, two hours, and three hours after a meal -- also known as post-meal blood sugar.

What should blood sugar be in the morning?

This is known as the fasting blood sugar in morning when you wake up without eating food for over 8 hours. writes ...

"A morning blood sugar reading below 70 indicates a hypoglycemic reaction, or low blood sugar condition. Blood sugar readings over 130 are considered high..."

Sometimes blood sugar can be high in the morning due to "dawn phenomenon" or the Somogyi effect.

The dawn phenomenon is the body's natural production of growth hormone, cortisol, and catecholamines during the latter half of sleep which tends to increase blood sugar.

The Somogyi effect is kind of like a "rebound hyperglycemia" when blood sugar drops too low during the night and the body counter regulates by increasing blood sugar, but then swinging slightly too high in the other direction.


This article was written in 2014 and is only opinion at the time of writing. I am not a doctor and this should not be considered medical advice.


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    • BlissfulWriter profile image

      BlissfulWriter 3 years ago

      For international units, is a good reference. A fasting blood sugar of above 6 mmol/l is a bit high and is something that one should watch out for.

    • manatita44 profile image

      manatita44 3 years ago from london

      Useful article.

      As individuals vary so much, I have found that 4.5 to 8.5 mmols/lto be relatively normal. One allows for 4mmols/l or 10 mmols/l on the higher scale but not more.

      Constant swings in diabetes creates potentially major problems for the heart, eyes, feet and kidneys in later life.

      Great article. Keep it up. Peace.