Back to Basics: Abnormal Blood Sugar Levels and the Diagnosis of Diabetes

by Cindy

Diabetes Mellitus: Understanding Blood Sugar Levels

High Blood Glucose
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Diabetes is a complex medical condition that affects more than 25 million Americans and this number continues to grow by approximately one million new patients per year!  This disorder is characterized by the disruption in the normal blood sugar levels, or homeostasis, within the body due to a series of metabolic changes.  Any disruption in this process can lead to abnormal glucose readings.

What are Normal Blood Sugar Levels?

  • Fasting:  Normal fasting blood sugar levels range between 60 to 100 mg/dl when fasting before meals but it takes a complex series of chemical reactions within the body to keep normal blood sugar in range.
  • Non-fasting:  Your blood glucose levels should remain lower than 140 mg/dl after meals.

Isolated readings that are outside of this range do not always mean that you have developed diabetes.  Read on to learn more about how this complicated process is regulated by several different hormones, the symptoms of this disorder, and what blood sugar levels are required to diagnose diabetes.

How the Body Regulates Blood Sugar Levels

As previously mentioned, diabetes is characterized by a disruption in the way that the body naturally processes glucose, or sugars.  Glucose is important because it is the body’s primary energy source.  Glucose is obtained through dietary intake of foods such as carbohydrates and fats.  There are several chemicals, or hormones, that are produced by the body which help it to regulate blood sugar levels in the correct range.  The hormones that are involved with regulation of normal blood sugar levels are insulin, glucagon and glucagon-like polypeptide-1 (GLP-1). Together they keep your blood sugar levels in a normal range.

What is Insulin? Insulin is a hormone that is produced by the beta cells within the pancreas.  This hormone is needed to remove sugars from the bloodstream and to send the glucose into cells where it can be used by the body for energy.

  • Insulin and Fasting Glucose Levels: Insulin is constantly released by the body to keep blood sugar levels in the normal blood sugar range of 60 to 100 mg/dl while fasting.
  • Insulin and Glucose Levels After Meals: Insulin is also released following meals to store sugars from your meal.  Blood sugar levels after eating typically remain less than 140 mg/dl.  When blood glucose rises beyond 140 mg/dl after meals this is considered impaired fasting glucose and represents that there is a disruption in normal insulin production.  When blood glucose after eating is higher than 200 mg/dl, this is diagnostic for diabetes.
  • Insulin and Diabetes: Proper function of insulin is critical in regulating normal blood sugar levels.  When too little insulin is produced it results in abnormal blood sugar levels that are outside of the acceptable range.  In addition, cells can become resistant to insulin which results in high blood glucose levels.  A combination of insulin resistance and decrease insulin production leads to the development of type 2 diabetes.

What is Glucagon?  Glucagon is another hormone that plays a role in regulating blood sugar levels.  When blood sugar levels within the body become too low, this hormone is used to release glucose that is stored within the liver and muscles.

What is GLP-1?  This hormone is produced within the intestinal tract and it is used to stimulate the release of insulin.  GLP-1 also decreases the release of the glucagon.  This hormone also plays a role in helping people to feel full after meals.  There are several medications, such as Byetta, which target the GLP-1 hormone to help the body regulate its own hormonal balance and keep glucose in the normal blood sugar range.

When this careful balance between insulin, glucagon and GLP-1 is disrupted, blood sugar levels can rise creating a state called hyperglycemia.  Diabetes occurs when this balance is disrupted by deficient, ineffective, and/or absent insulin.  Insulin deficiency can occur by many different mechanisms and can result in both partial and complete loss of the effectiveness and production of the hormone.  Once insulin deficiency occurs, blood glucose levels will begin to rise outside of the normal blood sugar range and patients will eventually be diagnosed with diabetes.

Types of Diabetes

There are three common types of diabetes that are characterized by differences in how the normal balance of glucose is disrupted; type 1 diabetes mellitus, type 2 diabetes mellitus and gestational diabetes mellitus.

Type 1 Diabetes: In type 1 diabetic patients, the pancreas is attacked by the immune system resulting in destruction of the insulin producing cells of the pancreas.  When this occurs, insulin is no longer produced by the body and hyperglycemia, or high sugar levels, result.

Type 2 Diabetes: In type 2 diabetic patients, a condition called insulin resistance develops where more insulin is needed to achieve normal blood sugar levels. In these patients, the pancreas produces more insulin to combat rising sugar levels but eventually the body will be unable to keep up with this demand resulting in persistently high sugar levels and the type 2 diabetic state. Ninety percent of diabetic patients have type 2 diabetes mellitus!

Gestational Diabetes:Gestational diabetes is a form of abnormal glucose metabolism that occurs only in pregnancy.

For more information about these types of diabetes and if they can be cured, check out my article “Is there a diabetes cure? The answer is not be as straightforward as you think.”

What Causes Diabetes?

There is not one specific cause of diabetes.  In fact, it is not actually known what causes either type of diabetes but many theories exist and it is thought that the following each play a role:


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  • Genetics: It is common for diabetes to run in families but the risks differ between type 1 and type 2 diabetes.  It is suspected that multiple genes contribute to the development of diabetes among family members.
  • Viruses:  It has long been hypothesized that viral infections may trigger an immune response that destroys the insulin producing cells in patients with type 1 diabetes.
  • Obesity:  Current research demonstrates that obesity is a major risk factor for the development of type 2 diabetes.
  • Age: Type 2 diabetes is more common among people over age 40.
  • Diet: Poor food choices may be partially to blame for the development of type 2 diabetes.
  • Other Causes: Stress, illness, medications and hormonal imbalances may contribute to the development of type 2 diabetes.

What are the Signs and Symptoms of Diabetes?

The classic symptoms of diabetes caused by significantly high blood sugar levels are:


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  • Polyuria (frequent urination)
  • Polydipsia: (increased thirst)
  • Polyphagia: (increased hunger)
  • Weight Loss
  • Blurred Vision

Other symptoms that are suggestive of diabetes include:

  • Fatigue
  • Itchy skin
  • Slow healing
  • Yeast infections: frequent yeast infections are common signs of diabetes in women
  • Erectile Dysfunction: impotence and erectile dysfunction are common signs of diabetes in men
  • Nervous system problems: numbness, tingling, burning in extremities known as diabetic neuropathy.

Who Should be Tested for Diabetes?

  • All overweight (BMI > 25) patients after age 45
  • All overweight (BMI > 25) patients before age 45 with additional risk factors such as:
    • Sedentary lifestyle
    • Family history of diabetes
    • High risk of diabetes due to ethnicity
    • History of gestational diabetes
    • History of hypertension
    • Abnormal cholesterol levels
    • Diagnosis of PCOS
    • History of abnormal blood glucose levels on previous testing

How is Diabetes Diagnosed?

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Diabetes is diagnosed using simple blood tests that will give your doctor information about how your body processes glucose.  To look for abnormal blood sugar levels your doctor will order the following tests:

The blood sugar levels charts below give a brief summary of the information that the fasting blood glucose and oral glucose tolerance tests provide and also indicates the normal range for blood sugar.  Each test provides your physican with slightly different information about if your blood sugar is outside the normal range. To learn more detailed information about how what these tests mean, check out my article “My Pancreas Failed Me. Now What Should My Blood Sugar Be? and “Did I Pass or Fail? Decoding the A1c Blood Test.”

Fasting Blood Sugar Levels Chart

  • Normal Fasting Blood Sugar Levels For Men & Women:  < 100 mg/dl
  • Impaired Fasting Blood Glucose Levels For Women & Men: 101 to 125 mg/dl
  • Fasting Blood Sugar Levels Diagnostic For Diabetes: > 126 mg/dl

Oral Glucose Tolerance Test Levels Chart

  • Normal Blood Sugar Range For OGTT: < 140 mg/dl
  • Impaired Glucose Tolerance Range: 141 to 200 mg/dl
  • Diabetic Glucose Tolerance Range: >200 mg/d

Diabetes is a complex disorder that has numerous health implications and requires prompt treatment with oral diabetes medications or insulin.  For patients that are diagnosed with diabetes, it is important to arm yourself with knowledge. Explore our site at KnowYourSugar to learn more about your condition!

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