Dr. MJ Bazos MD,
Glucose, a form of sugar, is the body's main
fuel. Hypoglycemia, or low blood sugar, occurs when blood levels of glucose drop
too low to fuel the body's activity.
Carbohydrates (sugars and starches)
are the body's main dietary sources of glucose. During digestion, the glucose is
absorbed into the blood stream (hence the term "blood sugar"), which carries it
to every cell in the body. Unused glucose is stored in the liver as glycogen.
Hypoglycemia can occur as a
complication of diabetes, as a condition in itself, or in association with other
Blood Sugar Range
The normal range for blood sugar is
about 60 mg/dl (milligrams of glucose per deciliter of blood) to 120 mg/dl,
depending on when a person last ate. In the fasting state, blood sugar can
occasionally fall below 60 mg/dl and even to below 50 mg/dl and not indicate a
serious abnormality or disease. This can be seen in healthy women, particularly
after prolonged fasting. Blood sugar levels below 45 mg/dl are almost always
associated with a serious abnormality.
How Does the Body Control Glucose?
The amount of glucose in the blood is
controlled mainly by the hormones insulin and glucagon. Too much or too little
of these hormones can cause blood sugar levels to fall too low (hypoglycemia) or
rise too high (hyperglycemia). Other hormones that influence blood sugar levels
are cortisol, growth hormone, and catecholamines (epinephrine and
The pancreas, a gland
in the upper abdomen, produces insulin and glucagon. The pancreas is dotted with
hormone-producing tissue called the islets of Langerhans, which contain alpha
and beta cells. When blood sugar rises after a meal, the beta cells release
insulin. The insulin helps glucose enter body cells, lowering blood levels of
glucose to the normal range. When blood sugar drops too low, the alpha cells
secrete glucagon. This signals the liver to release stored glycogen and change
it back to glucose, raising blood sugar levels to the normal range. Muscles also
store glycogen that can be converted to glucose.
What Are the Symptoms of
A person with
hypoglycemia may feel weak, drowsy, confused, hungry, and dizzy. Paleness,
headache, irritability, trembling, sweating, rapid heart beat, and a cold,
clammy feeling are also signs of low blood sugar. In severe cases, a person can
lose consciousness and even lapse into a coma.
The symptoms associated with
hypoglycemia are sometimes mistaken for symptoms caused by conditions not
related to blood sugar. For example, unusual stress and anxiety can cause excess
production of catecholamines, resulting in symptoms similar to those caused by
hypoglycemia but having no relation to blood sugar levels.
Hypoglycemia in Diabetes
The most common cause of hypoglycemia
is as a complication of diabetes. Diabetes occurs when the body cannot use
glucose for fuel because either the pancreas is not able to make enough insulin
or the insulin that is available is not effective. As a result, glucose builds
up in the blood instead of getting into body cells.
The aim of treatment in diabetes is to
lower high blood sugar levels. To do this, people with diabetes may use insulin
or oral drugs, depending on the type of diabetes they have or the severity of
their condition. Hypoglycemia occurs most often in people who use insulin to
lower their blood sugar. All people with insulin-dependent diabetes mellitus
(IDDM, or type 1) and some people with noninsulin-dependent diabetes mellitus
(NIDDM, or type 2) use insulin. People with type 2 diabetes who take oral drugs
called sulfonylureas are also vulnerable to low blood sugar episodes.
Conditions that can lead to
hypoglycemia in people with diabetes include taking too much medication, missing
or delaying a meal, eating too little food for the amount of insulin taken,
exercising too strenuously, drinking too much alcohol, or any combination of
these factors. People who have diabetes often refer to hypoglycemia as an
Hypoglycemia in Diabetes
diabetes should consult their health care providers for individual guidelines on
target blood sugar ranges that are best for them. The lowest safe blood sugar
level for an individual varies, depending on the person's age, medical
condition, and ability to sense hypoglycemic symptoms. A target range that is
safe for a young adult with no diabetes complications, for example, may be too
low for a young child or an older person who may have other medical problems.
Because they are attuned to the
symptoms, people with diabetes can usually recognize when their blood sugar
levels are dropping too low. They can treat the condition quickly by eating or
drinking something with sugar in it such as candy, juice, or nondiet soda.
Taking glucose tablets or gels (available in drug stores) is another convenient
and quick way to treat hypoglycemia.
People with IDDM are most vulnerable
to severe insulin reactions, which can cause loss of consciousness. A few
patients with long-standing insulin-dependent diabetes may develop a condition
known as hypoglycemia unawareness, in which they have difficulty recognizing the
symptoms of low blood sugar. For emergency use in patients with IDDM, physicians
often prescribe an injectable form of the hormone glucagon. A glucagon injection
(given by another person) quickly eases the symptoms of low blood sugar,
releasing a burst of glucose into the blood.
Emergency medical help may be needed
if the person does not recover in a few minutes after treatment for
hypoglycemia. A person suffering a severe insulin reaction may be admitted to
the hospital so that blood sugar can be stabilized.
People with diabetes can reduce or
prevent episodes of hypoglycemia by monitoring their blood sugar levels
frequently and learning to recognize the symptoms of low blood sugar and the
situations that may trigger it. They should consult their health care providers
for advice about the best way to treat low blood sugar. Friends and relatives
should know about the symptoms of hypoglycemia and how to treat it in case of
Episodes of hypoglycemia in
people with IDDM may become more common now that research has shown that
carefully controlled blood sugar helps prevent the complications of diabetes.
Keeping blood sugar in a close-to-normal range requires multiple injections of
insulin each day or use of an insulin pump, frequent testing of blood glucose, a
diet and exercise plan, and guidance from health care professionals.
Other Causes of Hypoglycemia
Hypoglycemia in people who do not have
diabetes is far less common than once believed. However, it can occur in some
people under certain conditions such as early pregnancy, prolonged fasting, and
long periods of strenuous exercise. People on beta blocker medications who
exercise are at higher risk of hypoglycemia, and aspirin can induce hypoglycemia
in some children. Drinking alcohol can cause blood sugar to drop in some
sensitive individuals, and hypoglycemia has been well documented in chronic
alcoholics and binge drinkers. Eating unripe ackee fruit from Jamaica is a rare
cause of low blood sugar.
To diagnose hypoglycemia in people who
do not have diabetes, the doctor looks for the following three conditions:
•The patient complains of symptoms of
•Blood glucose levels are measured while
the person is experiencing those symptoms and found to be 45 mg/dl or less in a
woman or 55 mg/dl or less in a man
•The symptoms are promptly relieved upon
ingestion of sugar.
For many years, the oral glucose tolerance
test (OGTT) was used to diagnose hypoglycemia. Experts now realize that the OGTT
can actually trigger hypoglycemic symptoms in people with no signs of the
disorder. For a more accurate diagnosis, experts now recommend that blood sugar
be tested at the same time a person is experiencing hypoglycemic symptoms.
The doctor will also check the patient
for health conditions such as diabetes, obtain a medication history, and assess
the degree and severity of the patient's symptoms. Laboratory tests to measure
insulin production and levels of C-peptide (a substance that the pancreas
releases into the bloodstream in equal amounts to insulin) may be performed.
A diagnosis of reactive hypoglycemia
is considered only after other possible causes of low blood sugar have been
ruled out. Reactive hypoglycemia with no known cause is a condition in which the
symptoms of low blood sugar appear 2 to 5 hours after eating foods high in
Ten to 20 years ago,
hypoglycemia was a popular diagnosis. However, studies now show that this
condition is actually quite rare. In these studies, most patients who
experienced the symptoms of hypoglycemia after eating glucose-rich foods
consistently had normal levels of blood sugar–above 60 mg/dl. Some
researchers have suggested that some people may be extra sensitive to the body's
normal release of the hormone epinephrine after a meal.
People with symptoms of reactive
hypoglycemia unrelated to other medical conditions or problems are usually
advised to follow a healthy eating plan. The doctor or dietitian may suggest
that such a person avoid foods high in carbohydrates; eat small, frequent meals
and snacks throughout the day; exercise regularly; and eat a variety of foods,
including whole grains, vegetables, and fruits.
Rare Causes of Hypoglycemia
Fasting hypoglycemia occurs when the
stomach is empty. It usually develops in the early morning when a person
awakens. As with other forms of hypoglycemia, the symptoms include headache,
lack of energy, and an inability to concentrate. Fasting hypoglycemia may be
caused by a variety of conditions such as hereditary enzyme or hormone
deficiencies, liver disease, and insulin-producing tumors.
In hereditary fructose intolerance, a
disorder usually seen in children, the body is unable to metabolize the natural
sugar fructose. Attacks of hypoglycemia, marked by seizures, vomiting, and
unconsciousness, are treated by giving glucose and eliminating fructose from the
Galactosemia, a rare genetic
disorder, hampers the body's ability to process the sugar galactose. An infant
with this disorder may appear normal at birth, but after a few days or weeks of
drinking milk (which contains galactose), the child may begin to vomit, lose
weight, and develop cataracts. The liver may fail to release stored glycogen
into the blood, triggering hypoglycemia.
Removing milk from the diet is the
A deficiency of
growth hormone causes increased sensitivity to insulin. This sensitivity occurs
because growth hormone opposes the action of insulin on muscle and fat cells.
For this reason, children with growth hormone deficiency sometimes suffer from
hypoglycemia, which goes away after treatment.
People with insulin-producing tumors,
which arise in the islet cells of the pancreas, suffer from severe episodes of
To diagnose these
tumors, called insulinomas, a doctor will put the patient on a 24- to 72-hour
fast while measuring blood levels of glucose, insulin, and proinsulin. High
levels of insulin and proinsulin in the presence of low levels of glucose
strongly suggest an insulin-producing tumor. These tumors are usually benign and
can be surgically removed.
cases, some cancers such as breast cancer and adrenal cancer may cause
hypoglycemia through secretion of a hormone called insulin-like growth factor
II. The treatment is removal of the tumor, if possible.