Oral Glucose Tolerance Test (OGTT)

What is Oral Glucose Tolerance Test?

The oral glucose tolerance test (OGTT), also known as the glucose tolerance test, is a lab test to how your the body’s ability to metabolize glucose, or clear it out of the bloodstream. In this procedure the The patient is asked to take a glucose drink and their blood glucose level is measured before and at intervals after the sugary drink is taken. The test can be used to diagnose diabetes, gestational diabetes  or prediabetes.

The test is a more substantial indicator of diabetes than finger prick testing

Why OGTT is Done?

According to webmd.com the Oral Glucose Tolerance Test is done to:

• Check pregnant women for gestational diabetes. You have an increased chance of developing gestational diabetes if you:
• Have had gestational diabetes during a previous pregnancy.
• Have previously given birth to a baby who weighed more than 9 lb (4.1 kg).
• Are younger than age 25 and were overweight before getting pregnant.
• Diagnose prediabetes.
• Diagnose Insulin resistance, and
• Reactive hypoglycemia

How to Prepare the Test?

For those who taking the test to diagnose diabetes or prediabetes, you must need first to prepare before performing the diagnostic test:

• You must eat a balanced diet that contains at least 150 grams (g) of carbohydrate per day for 3 days before the test. Fruits, breads, cereals, grains, rice, crackers, and starchy vegetables such as potatoes, beans, and corn are good sources of carbohydrate.
• Fasting at least 8 to 12 hours before your first blood sample is taken. Do not eat, drink, smoke, or exercise strenuously during the fasting.
• Must tell your doctor about all prescription and nonprescription medicines you are taking, because it will affect the test results. You may be instructed to stop taking certain medicines before the test.

How is Done?

After the preparation, on the day of testing, the following steps will be done:

• A blood sample will be collected when you arrive. This is your first blood taken to measure your blood sugar (glucose) level before the test. 
• The next stage is to take a very sweet tasting, glucose drink. It is best to drink the liquid quickly. For the standard glucose tolerance test, you will drink 75 grams or 100 grams. Pregnant women drink 75 grams of glucose.
• Further blood samples will then be taken either at regular intervals of say 30 or 60 minutes or a single test after 2 hours. The test could take up to 3 hours.Since activity can interfere with test results, you will be asked to sit quietly during the entire test. Do not eat during the test. You may drink only water during this time.

The Blood Test

The health professional taking a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

What Should the Test Result be?

For people without diabetes:

• Fasting value (before the test): under 6 mmol/L
• At 2 hours: under 7.8 mmol/L

For people with impaired glucose tolerance (IGT)

• Fasting value (before the test): under 6.0 to 7.0 mmol/L
• At 2 hours: under 7.9 to 11.0 mmol/L

For diabetic levels

• Fasting value (before the test): under 7.0 mmol/L
• At 2 hours: over 11.0 mmol/L

What do these OGT Test Results mean?

If you fall in the range within the impaired glucose tolerance, you will likely be advised to make lifestyle changes. In some cases, blood glucose lowering medication may be advised.

If you fall within the diabetic range, it is quite likely that blood glucose medication will be prescribed to help your body keep your blood glucose levels down.

National Institutes of Health (NIH) stated, that the OGTT it is better able to diagnose high blood glucose after a glucose challenge than the fasting blood glucose test. A doctor may recommend it if he or she suspects diabetes in cases where a patient’s fasting blood glucose level is normal. However, the test is more time-consuming and complicated than the fasting blood glucose test.

Source & References:

1. Glucose Tolerance Test - diabetes.co.uk Retrieved last February 26, 2013
2. Oral Glucose Tolerance Test  - Webmd.com. Retrieved last February 26, 2013 
3. Glucose Tolerance Test - nlm.nih.gov . Retrieved last February 27, 2013 
4. Image source: http://www.diabetesinfo.org.au/webdata/images/Glucose%20Tolerance%20Test.jpg. Retrieved last February 26, 2013

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Gestational Diabetes

What is Gestational Diabetes?

Gestational diabetes develops during pregnancy (gestation) - usually around the 24th week. About 2 and 10 percent of expectant mothers develop this condition, making it one of the most common health problems of pregnancy. Like other types of diabetes, gestational diabetes affects how your cells use sugar (glucose) in your body's main fuel. 

What causes Gestational Diabetes in Pregnancy? 

When you eat, your digestive system breaks most of your food down into a type of sugar called glucose. The glucose enters your bloodstream and then, with the help of insulin (a hormone made by your pancreas), your cells use the glucose as fuel. However, if your body doesn't produce enough insulin too much glucose remains in your blood instead of moving into the cells and getting converted to energy.

We don't know what causes gestational diabetes, but we have some clues. The placenta supports the baby as it grows. Hormones from the placenta help the baby develop. But these hormones also block the action of the mother's insulin in her body. This problem is called insulin resistance. Insulin resistance makes it hard for the mother's body to use insulin. She may need up to three times as much insulin. When insulin is not much sufficient to produce, the blood glucose levels rise too high, resulting in gestational diabetes.

Most women with gestational diabetes don't remain diabetic after the baby is born. Once you've had gestational diabetes, though, you're at higher risk for getting it again during a future pregnancy and for developing diabetes later in life.

How Gestational Diabetes can Affect your Baby?

Gestational diabetes affects the mother in late pregnancy, after the baby's body has been formed, but while the baby is busy growing. Because of this, gestational diabetes does not cause the kinds of birth defects sometimes seen in babies whose mothers had diabetes before pregnancy.

However, untreated or poorly controlled gestational diabetes can hurt your baby. When you have gestational diabetes, your pancreas works overtime to produce insulin, but the insulin does not lower your blood glucose levels. Although insulin does not cross the placenta, glucose and other nutrients do. So extra blood glucose goes through the placenta, giving the baby high blood glucose levels. This causes the baby's pancreas to make extra insulin to get rid of the blood glucose. Since the baby is getting more energy than it needs to grow and develop, the extra energy is stored as fat.

This can lead to macrosomia, or a "fat" baby. Babies with macrosomia face health problems of their own, including damage to their shoulders during birth. Because of the extra insulin made by the baby's pancreas, newborns may have very low blood glucose levels at birth and are also at higher risk for breathing problems. Babies with excess insulin become children who are at risk for obesity and adults who are at risk for type 2 diabetes.

Chances of Getting Gestational Diabetes

According to the American Diabetes Association your chances of getting gestational diabetes are higher if you...

• you're over 35 years old
• you're overweight
• have had gestational diabetes before
• have given birth to a baby weighing more than 9 pounds
• have a strongly family member with history of diabetes
• have high blood pressure
• have sugar in your urine.
• have too much amniotic fluid
• have had an unexplained miscarriage or stillbirth

A small number of women might be considered at such low risk that they might not have to get tested. You're part of this group if you meet all of the following criteria:

• You're younger than 25.
• Your weight is in a healthy range.
• You're not a member of any racial or ethnic group with a high prevalence of diabetes, including people of Hispanic, African, Native American, South or East Asian, Pacific Island, and indigenous Australian ancestry.
• None of your close relatives have diabetes.
• You've never had a high result on a blood sugar test.
• You've never had an overly large baby or any other pregnancy complication usually associated with gestational diabetes.

Symptoms of Gestational Diabetes

Usually there are no symptoms, or the symptoms are mild and not life threatening to the pregnant woman. The blood sugar (glucose) level usually returns to normal after delivery.

Symptoms may include:

• Blurred vision
• Fatigue
• Frequent infections, including those of the bladder, vagina, and skin
• Increased thirst
• Increased urination
• Nausea and vomiting
• Weight loss despite increased appetite

How will I Know if I have Gestational Diabetes?

Gestational diabetes usually has no symptoms. That's why almost all pregnant women have a glucose-screening test between 24 and 28 weeks.

However, if you're at high risk for diabetes or are showing signs of it (such as having sugar in your urine), your caregiver will recommend this screening test at your first prenatal visit and then repeat the test again at 24 to 28 weeks if the initial result is negative.

By the way, if you get a positive result on a glucose-screening test, it doesn't necessarily mean that you have gestational diabetes. It does mean that you'll need to take a longer follow-up test (a glucose tolerance test, or GTT) to find out.

References

1. Diabetes Basics Retrieved February 15, 2013
2. Gestational diabetes. Retrieved February 16, 2013 
3. Gestational diabetes. Retrieved February 18, 2013  

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