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What Are Normal Blood Sugar Levels?

Updated on December 26, 2015
What are normal blood sugar levels? Let us first look at how blood glucose behaves both in fasted and fed conditions
What are normal blood sugar levels? Let us first look at how blood glucose behaves both in fasted and fed conditions | Source

Sugar goes by many names and comes in many different forms in the food we eat.

Blood sugar is a measure of how much glucose is present in one’s blood. Blood tests done in the lab can determine if one’s body is processing glucose properly.

Minutes after consuming a meal, the digestive system begins breaking down carbohydrates into smaller usable molecules called glucose. Glucose molecules are then absorbed into the blood stream resulting to a rise in blood glucose level. Glucose-rich blood travels throughout the body and stimulates the pancreas to secrete insulin, a peptide hormone that triggers the uptake of glucose into cells where glucose can be metabolized to generate ATP – the main fuel for all body cells. Insulin also stimulates liver cells to convert glucose into glycogen which is the storage form for glucose in the liver. Insulin response is what drives down blood glucose back to normal – homeostasis.

After a meal, the pancreas drives blood sugar back to normal
After a meal, the pancreas drives blood sugar back to normal | Source

During fasting or prolonged exercise when blood glucose falls below normal, the pancreas jumps in to bring the blood glucose back up to normal. The pancreas secretes a hormone called glucagon which has an opposite effect to that of insulin. Glucagon promotes the conversion of glycogen stored in the liver back to glucose driving blood glucose back up to normal – homeostasis.

Glucose homeostasis is the tendency for the body to maintain stable blood glucose levels through careful regulation by hormone signals. That is, if blood glucose levels strays out of normal limits, the amount of insulin and glucagon are adjusted accordingly.

Normal Blood Sugar Levels

Blood glucose fluctuates throughout the day depending on food intake, exercise and other factors. Self-monitoring of blood glucose can be done by using a glucose meter. The standard unit for measuring blood glucose in the USA and Europe is milligrams per decilitre (mm/dL). In the UK, the most common unit for measuring blood glucose is millimol per litre (mmol/L).

  • Normal Fasting Blood Sugar Levels

Let’s now get to the nitty-gritty of which blood glucose levels are considered ‘normal’, hereafter referred to as normal blood sugar levels.

A preprandial blood sugar measurement is one taken before meal. It is usually measured after fasting for at least 8 hours, hence also referred to as fasting blood sugar. The normal fasting blood sugar in a healthy adult is around 80 mg/dL (that is 4.4 mmol/L). According to the American Diabetes Association (Standard of Medical Care in Diabetes), a normal fasting blood sugar for a non-pregnant adult should be between 70 and 100 mg/dL (which is 3.9 and 5.6 mmol/L).

Profile of normal blood sugar levels throughout the day
Profile of normal blood sugar levels throughout the day | Source
  • Normal Post-Meal Blood Sugar Levels

After a normal meal (postprandial), blood sugar level gradually goes up. In a healthy adult, about 45 minutes after the start of a meal, blood sugar spikes temporarily without reaching 140 mg/dL (7.8 mmol/L). It then starts dropping and will get below 100 mg/dL (5.6 mmol/L) at 2 hours after the start of the meal. Beyond 2 hours, it will return to fasting blood sugar range until the next meal. According to the American Diabetes Association (Standard of Medical Care in Diabetes), a normal blood glucose measured 1 to 2 hours after the start of a meal is one that is less than 140 mg/dL (7.8 mmol/L).

Type
Normal Range
Fasting Blood Sugar Level
70 – 100 mg/dL (3.9 to 5.6 mmol/L)
2 hours After Meal
under 140 mg/dL (under 7.8 mmol/L)
Source: Standard of Medical Care in Diabetes – 2008, American diabetes Association
Diabetes
Type I diabetes is when a person loses the ability to produce insulin. In Type II diabetes, a person has insufficient insulin to trigger the uptake of glucose into cells. There are people with type II diabetes who have sufficient insulin but the problem is that their cells are resistant to it.

Glucose Meter

Hypoglycemia
Hypoglycemia is a life-threatening condition that occurs when the amount of glucose in the blood drops to a dangerously low level. Hypoglycemia episodes are common in diabetics who use insulin or other glucose lowering medications. An attack can be caused by a very high level of insulin in the blood.

Abnormal Blood Sugar Levels

If your blood sugar measurements are persistently above the upper limits of normal, this may suggest that your body is not regulating blood sugar properly, this can be due to diabetes. On the other hand, when your blood sugar gets below 70 mg/dL, you develop low blood sugar referred to as hypoglycemia.

It is important to keep tabs on your blood sugar. there are many people walking around with a high risk of developing diabetes and they don’t even know it. Normal blood sugar level is individualized; it is based on your personal health situation, demographics and other factors.

So, talk to your doctor about your blood sugar test results and how often you need to check your blood sugar.

More on Diabetes

Final Comment

Normal blood sugar levels have not yet been accurately define. Normal ranges for blood sugar are used as a guide and they may vary from lab to lab.

Normal ranges for blood sugar is individualized; a more or a less strict normal range may be appropriate per individual depending on health and other factors. A normal blood sugar level is not necessarily a healthy blood sugar level. Even though the term ‘normal blood sugar levels’ is used, a result at the upper or lower border of the ‘normal’ range may still be indicating a health issue. Be sure to talk to your health care provider about your blood sugar.

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