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What to Know about Glucose Tolerance Test in Pregnancy

Glucose tolerance test enables the doctors to detect whether or not you have prediabetes, gestational diabetes or type 2 diabetes. To conduct these tests, you can drink glucose only and the doctor checks your blood to find out how the body reacts. Diabetes is related to certain conditions in which your body cannot process glucose effectively due to deficiency of insulin or resistance to insulin at the cellular level. This may be the reason for high blood sugar levels. As per research, diabetes is one of the major causes of death and each year the pregnant women experience gestational diabetes which will resolve after pregnancy.

Early diagnosis may be a key factor to proper treatment and lessen the risk of further complications. The doctors use glucose challenge test or oral glucose tolerance test (OGTT) for diagnosing diabetes. Go through this blogpost to know what these tests mean, when doctors perform them, what your results denote and other ways to be confirm you have diabetes.

How it works

Both OGTT and challenge test calculate the glucose levels in your body. The healthcare professional compares glucose levels before and after you take any sugary drinks. This allows them to know how your body will process glucose. The challenge test usually requires one hour while OGTT takes at least 2 to 3 hours. If you do not have diabetes, the glucose level will increase after which you can eat sugary foods and then return back to your routine habits. A person having diabetes find their sugar level becomes high and these tests help to measure this response.

Suitable candidate to conduct a glucose tolerance test

The test results help to denote whether or not the glucose level falls within prediabetes, diabetes or normal range.

People need to conduct the test when they are at greater risk of developing diabetes or have symptoms that indicate they have diabetes.

Pregnant women have to conduct this challenge test as the first step for toward ruling out their gestational diabetes. A person who is at lower risk of gestational diabetes will usually need to perform this test at 24–28 weeks of gestation.

In case of higher risk, the doctor may conduct the test early. If the test results are above their normal range, a person will usually perform the OGTT for confirmation.

Doctors may use challenge test and OGTT in non-pregnant women. There are some cases when they prefer fasting plasma glucose test which is easy and inexpensive than the OGTT.

What you can expect from the test

The test may be somewhat different based on whether a person is pregnant.

For pregnant women

They need to perform OGTT and glucose tolerance test in pregnancy. The procedure is as follows:

  • Glucose screening or challenge: The person conducts a blood test without fasting and takes glucose drink. After this, there is another blood test in the next 1 hour. If the result is 135–140 mg/dL or higher, the doctor may ask to perform OGTT.
  • OGTT: The person has fasting blood test and takes drink. Then there are further blood tests 1, 2, and maybe 3 hours later too.

Research shows that the doctor may have to draw blood in every hour for 2–3 hours to check for gestational diabetes. If two or more readings denote the person has high blood sugar levels, they may have gestational diabetes.

For non pregnant women

Women should probably undergo the glucose test during pregnancy. On the other hand, non pregnant women will have to conduct OGTT and they have to fast for at least 8 hours before performing the test.

It is necessary to inform the doctor early if you:

  • take regular medications
  • follow exercise regimens
  • have health problems

Research suggests that a person may eat typical diet that includes at least 150 grams of carbohydrates per day such as rice, pasta, bread and crackers for 3 days before the test.

The doctor may advise on how to take regular medications during the fasting period.

On the day of your test, the healthcare professional will:

  • take the blood sample before starting the test
  • ask you to take a sugary drink which has glucose and water
  • take blood samples 30, 60, 90, and 120 minutes  after you consume the drink

Test results

The test result denotes whether a person has diabetes or is at higher risk of developing it. When the result denotes you have prediabetes or diabetes, the doctor will discuss about possible treatment options.

Certain medications as well as other factors cause high blood glucose levels. Sometimes, a doctor will perform different tests or repeat the tests again for confirming the results.


If the test results suggest that the blood sugar levels are high, the doctor may suggest:

  • follow a healthy diet for gestational diabetes
  • monitor the blood sugar levels
  • use supplement insulin in certain cases
  • monitor blood sugar levels
  • have frequent prenatal care visits

The healthcare professionals will advise on the requirements and treatment plan of the person since diabetes affects everyone in a different way.

See our doctors at Private Blood Tests London to conduct glucose challenge test and get the results on time.