Step 13: Glucose Monitoring

Glucose is the principal carbohydrate found in blood and serves as an energy source. Glucose is also found in urine, cerebrospinal fluid and semen.

The glucose test screens for glucose disorders such as liver dysfunction and hypoglycemia—a low blood glucose level. Another glucose disorder is hyperglycemia, which is a high blood glucose level. Hyperglycemia may indicate diabetes mellitus, Cushing’s syndrome or an acute response to stress.

There are many portable glucose analyzers designed for both personal use and the medical office.

There are a variety of testing methods to diagnose, evaluate and monitor glucose. Let’s discuss a few of these.

Fasting Blood Glucose

Examining a patient’s fasting blood glucose (FBG) levels can screen for diabetes mellitus. A normal fasting serum value is less than 100 deciliters (dL). According to the American Diabetes Association, the prediabetes range is between 100 mg/dL and 125 mg/dL. Diabetes is diagnosed at fasting blood sugar of greater than or equal to 126 mg/dL.3

Diabetes mellitus is a chronic syndrome of insufficient insulin production that leads to the body’s inability to metabolize carbohydrates, protein and fat. The disease has a genetic component, but its development also depends on the individual’s environment and lifestyle, including diet, weight and exercise habits. Diabetes mellitus occurs as type 1 or type 2 diabetes.

Type 2 diabetes is the result of a problem in the way the body produces or uses insulin. This is the most common form of diabetes. Family history and genetics play a large role in the development of type 2 diabetes. Low activity levels, poor diet and excess body weight—especially around the waist—significantly increase the risk for type 2 diabetes.

Type 1 diabetes is a chronic disease that occurs when the pancreas does not produce enough insulin to properly control blood sugar levels. In type 1 diabetes, the body cannot make its own insulin; therefore, the patient must take insulin every day. For this reason, the condition is also known as insulin-dependent diabetes. In the past, type 1 diabetes was known as juvenile onset diabetes because, although it can affect any age, it is most often diagnosed in children, adolescents or young adults.

Secondary diabetes mellitus is defined as a diabetic condition that does not result from genetics or environmental conditions; it is always caused by another condition or event.

In order to accurately test patients’ FBG levels, they’ll need to fast for 12 hours before the test. Patients can drink water, though. Some medications such as oral contraceptives, diuretics and steroids can alter the test results, so the physician may have patients avoid them if possible. Patients should have written and verbal instructions in order to properly prepare for the glucose test.

Online Learning

Build on what you are learning by watching the video and reading the article Control your blood sugar levels.

Two-hour Postprandial Blood Glucose

Blood glucose can also be tested after eating using the two-hour postprandial blood glucose test. The two-hour postprandial screens blood glucose levels for diabetes and can help monitor insulin dosage. Usually, the patient is asked to fast after midnight and prescribed a meal or solution with a certain number of carbohydrates. Two hours later, a blood specimen is drawn and tested for glucose levels.

Only a minority of patients with diabetes mellitus have the classic symptoms of polyuria, polyphagia, polydipsia and weight loss. The two-hour postprandial glucose is extensively used to establish the diagnosis of diabetes mellitus. It may be used along with FBS to follow patients with impaired glucose tolerance.

Glucose Tolerance Test

The glucose tolerance test (GTT) is used to test insulin response and diagnose diabetes. The most common glucose tolerance test is the oral glucose tolerance test (OGTT). Like other glucose tests, the patient needs to fast for the GTT. The patient should only have water during the 10 hours prior to the test.

In order to make sure the patient can take the GTT, you have to determine the patient’s FBG level once he arrives for the test. If the level is more than 200 mg/dL, then a urine sample is taken and you draw blood through venipuncture. Make sure these specimens are labeled as fasting specimens along with the date and time of the draw. In addition, the physician should be notified.

If the FBG level is less than 200 mg/dL, then the patient can continue with the GTT. The patient must consume 75 to 100 grams of glucose solution within five minutes. Note what time the patient has finished the solution. Then, the patient’s urine and blood are tested at 30 minutes, one hour, two hours, three hours and sometimes six hours after ingestion. These tests will help determine how the patient deals with increased glucose.

During the testing period, the patient should not smoke, eat or chew gum. Otherwise, the test results could be incorrect. Drinking water is allowed.

After two or three hours, the patient may experience symptoms such as weakness, faintness and increased perspiration. However, if the patient complains of a headache, faints or is behaving and speaking oddly, the patient may be suffering from hypoglycemic shock—contact the physician immediately.

After two to three hours, a patient without diabetes will have a glucose level equal to his fasting level. A patient with diabetes will have increased glucose levels even at the end of the test. With the OGTT, diabetes is diagnosed at two hours with blood sugar of greater than or equal to 200 mg/dL.4

Automated Glucose Analyzers

Handheld, inexpensive glucose meters are instruments that measure glucose levels and provide rapid results when analyzing glucose. As with all instruments, it must be used correctly to get accurate results. One type of glucose meter, or analyzer, uses photometry to measure glucose levels. Photometry is the science of the measurement of light, as perceived by the human eye. A microcuvette, or small plastic container holding reagents, fills with blood from a capillary puncture and is placed into the photometer. In 45 to 240 seconds, a glucose concentration is displayed.

Another system uses reflectance photometry for glucose testing. Blood is applied to a test strip, which reacts with reagents in the pad. The reaction causes a color to form. Usually, the darker or more intense the color, the more glucose is present. Then, the test strip is inserted into a test chamber and a light shines on it. The photometer measures the amount of light that is reflected from the colored strip.

A glucose meter (glucometer) is a medical device for determining the approximate concentration of glucose in the blood; it assists patients to better manage their diabetes by tracking fluctuations in their blood glucose levels. There are a variety of different hand-held glucometers on the market that have unique features, but they all test in the same way. Glucometers are portable glucose meters that test a drop of blood on a test strip. These are convenient for the diabetic patient. As technological advances are made, the tests are becoming less painful, making testing compliance more consistent. There are now monitors that attach to the belt or skin that test throughout the day.

Often, the blood sample can be collected with a capillary puncture. However, a blood draw may be necessary. For the glucose blood draw, the phlebotomist will fill the green tube for a plasma specimen. You will use the gray top tube for a fasting glucose specimen.

Virtual Lab: Screen Glucose Level

 

 

Equipment Needed: Glucose analyzer, control solution, test strips for analyzer, gloves, goggles, lancet, alcohol swab, dry cotton balls, paper towel, sharps container

1. Turn on the analyzer.
2. Identify the patient and explain the procedure. Verify that the patient has met the pretesting requirements.
3. Wash your hands.
4. Put on gloves and protective goggles.
5. Record the control ranges, lot number and test strip lot number.
6. Perform the analyzer check test and control test. If both tests are within range, proceed to the glucose test.
7. Remove a test strip from the bottle.
8. Perform the capillary puncture. Place the used lancet in a sharps container immediately.
9. Apply a large drop of blood to the test strip.
10. Blot the test strip with a tissue as recommended by the manufacturer.
11. Insert the test strip into the test chamber.
12. Read the glucose results at the appropriate time interval.
13. Document the reading.
14. Dispose of all waste in a biohazard waste container.
15. Remove gloves and dispose of in a biohazard container.
16. Wash your hands.

 

If you prefer to take notes by hand, you can type them into the box below. These notes will be added to your Notes & Highlights page and can only be seen by you. This is also where you can disable My Notebook if you don't want to use it. Click the blue "My Notebook" box below to show or minimize it.

vertical_align_top

• Highlight
 
• Underline
 
• Bold