Diabetes Mellitus (cont.)
What are diabetes symptoms?
- The early symptoms of untreated diabetes are related to
elevated blood sugar levels, and loss of glucose in the urine. High amounts of
glucose in the urine can cause increased urine output and lead to
dehydration.
Dehydration causes increased thirst and water consumption.
- The inability of
insulin to perform normally has effects on protein, fat and carbohydrate
metabolism. Insulin is an
anabolic hormone, that is, one that encourages storage of fat and protein.
- A
relative or absolute insulin deficiency eventually leads to
weight loss despite an
increase in appetite.
- Some untreated diabetes patients also complain of fatigue,
nausea and
vomiting.
- Patients with diabetes are prone to developing infections
of the bladder, skin, and vaginal areas.
- Fluctuations in blood
glucose levels can lead to blurred vision. Extremely elevated glucose levels can
lead to lethargy and
coma.
How is diabetes diagnosed?
The fasting blood glucose (sugar) test is the preferred way to diagnose
diabetes. It is easy to perform and convenient. After the person has fasted
overnight (at least 8 hours), a single sample of blood is drawn and sent to the
laboratory for analysis. This can also be done accurately in a doctor's office
using a glucose meter.
- Normal fasting plasma glucose levels are less than 100
milligrams per deciliter (mg/dl).
- Fasting plasma glucose levels of more than 126
mg/dl on two or more tests on different days indicate diabetes.
- A random blood glucose test
can also be used to diagnose diabetes. A blood glucose level of 200 mg/dl or
higher indicates diabetes.
When fasting blood glucose stays above 100mg/dl, but in
the range of 100-126mg/dl, this is known as impaired fasting glucose (IFG).
While patients with IFG do not have the diagnosis of diabetes, this condition carries with it
its own risks and concerns, and is addressed elsewhere.
The oral glucose tolerance test
Though not routinely used anymore, the
oral glucose tolerance test
(OGTT)
is a gold standard for making the diagnosis of type 2
diabetes. It is still commonly used for diagnosing gestational diabetes and in
conditions of pre-diabetes, such as
polycystic ovary syndrome. With an
oral glucose tolerance test, the person fasts overnight (at least eight but not more
than 16 hours). Then first, the fasting plasma glucose is tested. After this
test, the person receives 75 grams of glucose (100 grams for pregnant women). There are
several methods employed by obstetricians to do this test, but the one described
here is standard. Usually, the glucose is in a sweet-tasting liquid that the
person drinks. Blood samples are taken at specific intervals to measure the
blood glucose.
For the test to give reliable results:
- the person must be
in good health (not have any other illnesses, not even a cold).
- the person
should be normally active (not lying down, for example, as an inpatient in a hospital), and
- the person should
not be taking medicines that could affect the blood glucose.
- For three days before
the test, the person should have eaten a diet high in carbohydrates (200-300
grams per day).
- The morning of the test, the person should not smoke or drink
coffee.
The classic oral glucose tolerance test measures blood
glucose levels five times over a period of three hours. Some physicians simply get a
baseline blood sample
followed by a sample two hours after drinking the glucose solution. In a person
without diabetes, the glucose levels rise and then fall quickly. In someone with
diabetes, glucose levels rise higher than normal and fail to come back down as
fast.
People with glucose levels between normal and diabetic have impaired glucose
tolerance (IGT). People with impaired glucose tolerance do not have diabetes,
but are at high risk for progressing to diabetes. Each year, 1%-5% of people
whose test results show impaired glucose tolerance actually eventually develop
diabetes. Weight loss and
exercise may help people with impaired glucose
tolerance return their glucose levels to normal. In addition, some physicians
advocate the use of medications, such as
metformin (Glucophage), to help
prevent/delay the onset of overt diabetes.
Recent studies have shown that
impaired glucose tolerance itself may be a risk factor for the development of
heart disease. In the medical community, most physicians are now understanding
that impaired glucose tolerance is nor simply a precursor of diabetes, but is
its own clinical disease entity that requires treatment and monitoring.
Evaluating the results of the oral glucose tolerance test
Glucose tolerance tests may lead to one of the following diagnoses:
- Normal response: A person is said to have a normal response when the 2-hour
glucose level is less than 140 mg/dl, and all values between 0 and 2 hours are
less than 200 mg/dl.
- Impaired glucose tolerance: A person is said to have impaired glucose
tolerance when the fasting plasma glucose is less than 126 mg/dl and the 2-hour
glucose level is between 140 and 199 mg/dl.
- Diabetes: A person has diabetes when two diagnostic tests done on different
days show that the blood glucose level is high.
- Gestational diabetes: A woman has gestational diabetes when she has any two
of the following: a 100g OGTT, a fasting plasma glucose of more than 95 mg/dl, a
1-hour glucose level of more than 180 mg/dl, a 2-hour glucose level of more than
155 mg/dl, or a 3-hour glucose level of more than 140 mg/dl.
Next: Why is blood sugar checked at home? »
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