Low Blood Sugar Symptoms and Ranges

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Quick GuideBlood Sugar Swings: Tips for Managing Diabetes & Glucose Levels

Blood Sugar Swings: Tips for Managing Diabetes & Glucose Levels

What is low blood sugar (hyperglycemia)?

Hypoglycemia or low blood sugar is syndrome that results from low blood sugar. The severity and symptoms of hypoglycemia can vary from person to person. Blood tests can diagnose low blood sugar, and symptoms resolve when the levels of sugar in the blood return to the normal range. The medical term for blood sugar is blood glucose.

Who gets low blood sugar?

While people who do not have any metabolic problems can complain of symptoms that resemble low blood sugar, but true hypoglycemia usually people with diabetes mellitus (type 1 and type 2) usually get it. People with pre-diabetes who have insulin resistance also can have low blood sugars on occasion if their high circulating insulin levels are further challenged by a prolonged period of fasting. There are other rare causes for the condition, such as insulin producing tumors (insulinomas) and certain medications. These uncommon causes of hypoglycemia will not be discussed in this article, which will primarily focus on the condition occurring with type 1 or 2 diabetes and its treatment.

Despite advances in the treatment of diabetes, low blood sugar episodes often are the limiting factor in achieving optimal blood sugar control, because many medications that are effective in treating diabetes carry the risk of lowering the blood sugar level too much, causing symptoms of the condition. In large scale studies looking at tight control in both type 1 and type 2 diabetes, low blood sugars occurred more often in the patients who were managed most intensively. This is important for patients and physicians to recognize, especially as the goal for treating patients with diabetes becomes tighter control of blood sugar.

Why is low blood sugar dangerous?

When the circulating level of blood glucose falls, the brain actually senses the drop. The brain then sends out messages that trigger a series of events, including changes in hormone and nervous system responses that are aimed at increasing blood glucose levels. Insulin secretion decreases and hormones that promote higher blood glucose levels, such as glucagon, cortisol, growth hormone, and epinephrine all increase. As mentioned previously, there is a store in the liver of glycogen that can be converted to glucose rapidly.

In addition to the biochemical processes that occur, the body starts to consciously alert the affected person that it needs food by causing the signs and symptoms of hypoglycemia.

The body needs fuel to work. One of its major fuel sources is sugars, which the body gets from what is consumed as either simple sugar or complex carbohydrates in the diet. For emergency situations (like prolonged fasting), the body stores a stash of sugar in the liver as glycogen. If this store is needed, the body goes through a biochemical process to make new sugar (gluco-neo-genesis) and converts these stores of glycogen to sugar. This backup process emphasizes that the fuel source of sugar is important (important enough for human beings to have developed an evolutionary system of storage to avoid a sugar deficit).

Of all the organs in the body, the brain depends on sugar (glucose) almost exclusively. Rarely, if absolutely necessary, the brain will use ketones as a fuel source, but this is not preferred. The brain cannot make its own glucose and is 100% dependent on the rest of the body for its supply. If for some reason, the glucose level in the blood falls (or if the brain's requirements increase and demands are not met) there can be effects on the function of the brain.

Medically Reviewed by a Doctor on 2/21/2017

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