Diabetes Mellitus


Diabetes Diagnosis and Monitoring

The diagnosis of diabetes requires drawing a blood sample to measure the concentration of glucose.  Like any disease, though, not every patient needs to be tested at every office visit.  Health professionals use risk factors and signs and symptoms as hints that testing for diabetes may be necessary.

Signs and Symptoms of Diabetes

The classic symptoms of
diabetes are excessive
thirst and frequent urination.

The classic symptoms of diabetes are polyuria (excessive urination) and polydipsia (excessive thirst).  As glucose begins to enter the urine, the concentrated sugar draws water out of the body, resulting in rapid urine production and frequent need to urinate.  As water is lost, the body responds by stimulating thirst centers in the brain.  The patient drinks, but the cycle of water loss and thirst continues as long as blood glucose is elevated.  Other symptoms include excessive hunger, fatigue, and blurry vision.  However, many patients with diabetes will experience no symptoms at all.  If you do find yourself suffering from these symptoms, mention them to your doctor.  He or she will assess your diabetes risk factors and help you decide whether diabetes testing is right for you.

Diagnostic Glucose Testing

There are several ways blood glucose can be checked.  The simplest method is to measure glucose in a random blood sample drawn from a vein in the arm.  While a very high value in this test (> 200 mg/dL) can be diagnostic of diabetes, it is possible for someone to have a higher-than-normal glucose level and not truly have diabetes.  For example, shortly after a meal, the blood glucose level may be briefly elevated even in a non-diabetic person.  A more accurate test is the fasting glucose level.  For this test, the patient is instructed to have no food or drink (except water) after midnight or on the morning of the test.  This gives the body plenty of time to store any excess blood glucose.  When glucose is measured in a fasting blood sample, a value > 126 mg/dL indicates a diagnosis of diabetes.  Usually the test is repeated at a later visit for confirmation. 

Diabetes is diagnosed by measuring glucose in the blood

The final test that may be used is the glucose tolerance test.  The preparation is the same as for the fasting test (no food or drink after midnight), but after the fasting blood is drawn, the patient is given a drink with a high concentration of glucose.  Two hours later, another blood sample is drawn.  Comparing the levels provides a good assessment of how well the body is able to process glucose.  Your doctor may have other variations of the test, including a special diet for several days beforehand or different intervals of blood sampling.  While the glucose tolerance test is the most sensitive way to detect diabetes (lowest chance of missing the diagnosis), it is not frequently performed due to preparation, cost, and time commitment constraints.  Your doctor will consider your symptoms and risk factors for diabetes when recommending which test to perform.

Follow-Up Testing

The portable glucose monitor
is a quick and inexpensive
way to check blood glucose levels.

Diagnosing diabetes is only the first step.  Once a treatment plan is agreed upon by you and your doctor, frequent check-ups are needed to how well the glucose level is being controlled.  One way is simply to check the blood glucose level, which can be done using a hand-held glucose monitor.  This test is not as accurate as the formal tests discussed above, but it is inexpensive, quick, and less uncomfortable and provides a pretty good assessment of current glucose levels.  The kit usually includes a small pin or device for pricking the finger to produce a small droplet of blood.  This sample is blotted onto a test strip, and the electronic monitor gives a reading in just a few seconds.  These glucose checks will likely be done at each visit to your doctor, and you may even be prescribed a monitor for home use, especially if you are using insulin or other glucose lowering medicines.

The one drawback of the glucose monitor is that it only gives the current blood glucose value, giving no information about long-term glucose control.  A patient may go 2 months with unacceptably high glucose levels only to skip breakfast on the day of the doctor’s visit and get a “normal” glucose reading.  Fortunately, another test, the Hb-A1C level, provides the missing information.  Hemoglobin (Hb) is a protein found in the blood that carries oxygen to all parts of the body.  When there is too much glucose in the blood, the glucose “sticks” to Hb, creating an alternate form called Hb-A1C.  This form persists for weeks unchanged.  If glucose levels have been high in the few weeks before your blood is drawn, even if the glucose level that day is normal, Hb-A1C will be elevated, indicating that better glucose control is needed.

Next, we will review the treatment options that are available for diabetes.

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