What is hypoglycemia?
Hypoglycemia is the clinical syndrome that
results from low blood sugar. The symptoms of hypoglycemia can vary from
person to person, as can the severity. Classically, hypoglycemia is
diagnosed by a low blood sugar with symptoms that resolve when the sugar
level returns to the normal range.
Who is at risk for
hypoglycemia?
While patients who do not have any metabolic
problems can complain of symptoms suggestive of low blood sugar, true
hypoglycemia usually occurs in patients being treated for diabetes (type 1
and type 2). Patients with pre-diabetes who have insulin resistance can also
have low sugars on occasion if their high circulating insulin levels are
further challenged by a prolonged period of fasting. There are other rare
causes for hypoglycemia, 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 hypoglycemia
occurring with diabetes mellitus and its treatment.
Despite our advances in the treatment of
diabetes, hypoglycemic episodes are often the limiting factor in achieving
optimal blood sugar control. 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 become tighter blood sugar control.
I thought high blood sugar
was bad. Why is low blood sugar also bad?
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. 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 called gluco-neo-genesis (meaning to “make new sugar”) 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 drought).
Of all the organs in the body, the brain
depends on sugar (which we are now going to refer to as 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.
Can the body protect itself
from hypoglycemia?
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 above, 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 is
needs food by causing the signs and symptoms of hypoglycemia discussed
below.
What are symptoms of
hypoglycemia, and how low is too low?
The body’s biochemical response to
hypoglycemia usually starts when sugars are in the high/mid 60’s. At this
point, the liver releases its stores and the hormones mentioned above start
to activate. In many patients, this process occurs without any clinical
symptoms.
While there is some degree of variability
among people, most will usually develop symptoms suggestive of hypoglycemia
when blood glucose levels are lowered to the mid 50’s. The first set of
symptoms are called neuro-genic (or sympathetic) because they relate to the
nervous system’s response to hypoglycemia. Patients may experience any of
the following;
- nervousness,
- sweating,
- intense hunger,
- trembling,
- weakness,
- palpitations, and
- often have trouble speaking.
In most patients, these symptoms are easily
recognizable. The vast majority of patients with diabetes only experience
this degree of hypoglycemia if they are on medications or insulin. Patients
(diabetic or with insulin resistance) with high circulating levels of
insulin who fast or lower their carbohydrate intake drastically should also
be cautioned. These patients may also experience modest hypoglycemia.
Anyone who has experienced an episode of
hypoglycemia describes a sense of urgency to eat and resolve the symptoms.
And, that’s exactly the point of these symptoms. They act as warning signs.
At this level, the brain still can access circulating blood glucose for
fuel. The symptoms provide a person the opportunity to raise blood glucose
levels before the brain is affected.
If a person does not or cannot respond by
eating something to raise blood glucose, the levels of glucose continue to
drop. Somewhere in the 45 mg/dl range, most patients progress to
neuro-glyco-penic ranges (the brain is not getting enough glucose). At this
point, symptoms progress to confusion, drowsiness, changes in behavior, coma
and seizure.
How is hypoglycemia
treated?
The acute management of hypoglycemia involves
the rapid delivery of a source of easily absorbed sugar. Regular soda,
juice, lifesavers, table sugar, and the like are good options. In general,
10-15 grams of glucose is used, followed by an assessment of symptoms and a
blood glucose check if possible. If after 10 minutes there is no
improvement, another 10-15 grams should be given. This can be repeated up to
3 times. At that point, the patient should be considered as not
responding to the therapy and an ambulance should be called.
The equivalency of 10-15 grams of glucose
(approximate servings) are:
- Ten lifesavers
- 4 teaspoons of sugar
- 1/2 can of regular soda or juice
Many people like the idea of treating
hypoglycemia with cake, cookies, and brownies. However, sugar in the form of
complex carbohydrates or sugar combined with fat and protein are much too
slowly absorbed to be useful in the acute treatment of hypoglycemia.
Once the acute episode has been treated, a
healthy, long-acting carbohydrate to maintain blood sugars in the
appropriate range should be consumed. Half a sandwich is a reasonable
option.
If the hypoglycemic episode has progressed to
the point where the patient cannot or will not take anything by mouth, more
drastic measures will be needed. In many cases, a family member or roommate
can be trained in the use of glucagon. Glucagon causes a rapid release of
glucose stores from the liver. It is an injection given intramuscularly to a
patient who cannot take glucose by mouth. A response is usually seen in
minutes and lasts for about 90 minutes. Again, a long-acting source of
glucose should thereafter be consumed to maintain blood sugar levels in the
safe range. If glucagon is not available and the patient is not able to take
anything by mouth, Emergency 911 should be called immediately. An
intravenous route of glucose administration should be established as soon as
possible.
With a history of recurrent hypoglycemic
episodes, the first step in treatment is to assess whether the hypoglycemia
is related to medications or insulin treatment. Patients with a consistent
pattern of hypoglycemia may benefit from a dose adjustment. It is important
that patients check blood glucose values multiple times a day to help define
whether there is a pattern with meals or medications.
Is there anything else that
should be done to manage hypoglycemia?
Yes. Patients should wear identification
stating they have diabetes and whether they have recurrent hypoglycemia.
Patients at risk for hypoglycemia should be counselled on checking blood
sugars before they drive a car, operate heavy machinery and do anything
physically taxing. In addition, patients should carry a quick-acting glucose
source (such as those mentioned above) at all times, and keep a source in
their car, office, and by their bedside. Efforts should be made to minimize
the hypoglycemic effects of medication regimens and to avoid variable surges
in exercise, activity and alcohol consumption.
For more in-depth information about diabetes,
please read the
Diabetes article.
Last Editorial Review: 6/22/2005
© 2007 MedicineNet, Inc. All rights reserved.
MedicineNet does not provide medical advice, diagnosis or treatment.
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