Why Would I Need This Test
You might need this test if you are at risk of developing diabetes, or if you have had any symptoms or test results suggesting diabetes.
The standard blood glucose tests measure your blood sugar level at a particular time. The OGTT measures how you respond to glucose.
Pregnant women can develop a particular type of diabetes called gestational diabetes, and will be asked to have an OGTT around 24 to 28 weeks of pregnancy. Gestational diabetes usually goes away after the baby is born.
Requirements Prior To The Test
- You are to remain on a normal, unrestricted diet for at least 3 days prior to test.
- You have had no acute significant illness for 2 weeks prior to test.
- Fasting is required for a period of 8-10 hours prior to the test. You may have sips of water if you are thirsty.
- Due to the nature of the test, testing is generally done in the morning.
- Maintain normal activity prior to the test.
- Bring a list of any current medications with you to the collection centre.
- Avoid smoking for one hour before and during test.
- Before drinking the glucose, please inform the collection staff if you have any allergies.
Other Blood Tests That Require Fasting
People may be asked to fast for:
- Blood glucose test: This tests the sugar in a persons blood and can help confirm or rule out diabetes.
- Liver function test: This
When people eat food and drink alcohol, the food and liquid get broken down in their stomach and absorbed into the bloodstream. This can affect the levels of certain substances in the blood, such as blood glucose or cholesterol.
Measuring the levels of these substances is crucial to diagnose certain conditions, such as:
- high cholesterol
For correct diagnosis of these conditions, it is important that a person fasts. Eating or drinking before the test may raise the levels of a particular substance in the blood, leading to inaccurate results. Incorrect results could in turn lead to an incorrect diagnosis.
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Medication And Blood Tests
Even if you are asked to fast for blood work, you should take your prescribed medications with water, unless specifically requested not to do so.
The exception to this is vitamins and supplements. These may affect certain lab tests, so they should be held the morning of a lab test.
Discuss what medications you are taking with your healthcare provider and clarify ahead of time if you have any questions on holding medications before blood work.
How To Lower Your Blood Glucose Levels
Even if you have a normal glucose screening and never test positive for glucose in your urine, its still important to follow a healthy diet during pregnancy, which can help stabilize your blood sugar levels.
Here are some tips on what to eat to keep blood sugar spikes at bay, plus other smart strategies:
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Avoid Sugars And Refined Carbs
Dont eat high-sugar foods or simple carbs the morning of your glucose screening. The body breaks these foods down quickly, leading to a spike in blood sugar levels. That means avoiding breakfast favorites like:
- Orange juice and other fruit juices
- Sweetened toppings like jam or syrup
- Pancakes, waffles and French toast
Can You Drink Alcohol If Youre Fasting Before A Blood Test
Some blood tests, such as those that assess liver health or triglyceride levels, may require you to not drink any alcohol for a full 24 hours. Trace amounts of alcohol can remain in your bloodstream for several days. If you have any concerns about alcohol consumption, discuss this with your doctor when you schedule your test.
Also ask your doctor if you can smoke cigarettes before the test, or if you should refrain from smoking during your fast.
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Can You Drink Water Before A Blood Test
Typically, water is the one thing you can have while fasting for a blood test. Drinking water can actually be useful before your test.
Drinking water before a blood test can help hydrate and plump up your veins. This can make it easier for the technician to find your veins and draw your blood. Water can also help keep your blood pressure from dropping during the blood draw.
What Are Blood Glucose Tests Used To Diagnose
Glucose testing is primarily done to diagnose or manage type 1 diabetes, type 2 diabetes, and gestational diabetes. Diabetes is a condition that causes your blood glucose levels to rise.
The amount of sugar in your blood is usually controlled by a hormone called insulin. But if you have diabetes, your body either doesnt make enough insulin or the insulin produced doesnt work properly. This causes sugar to build up in your blood.
If left untreated, chronically elevated levels of blood sugar can lead to other serious conditions including kidney disease, blindness, and heart disease.
In some cases, blood glucose testing may also be used to test for hypoglycemia. This condition occurs when the levels of glucose in your blood are too low, usually lower than 70 milligrams per deciliter .
Hypoglycemia can occur in people with diabetes if they take too much of their medication, like insulin, exercise more than usual, or skip a meal. Less commonly, hypoglycemia can be caused by other underlying conditions or medications.
Doctors consider very low blood sugar to be a medical emergency, as it can lead to seizures, coma, and even death.
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Gain The Right Amount Of Weight
Gaining too much or too quickly during pregnancy can increase the chances for GD, so talk to your doctor about what you should be seeing on the scale. In general, you should aim to gain 25 to 35 pounds if your pre-pregnancy body mass index was in the normal range, 15 to 25 pounds if you were overweight before becoming pregnant, and 11 to 20 pounds if you were obese before coming pregnant.
From the What to Expect editorial team and Heidi Murkoff, author of What to Expect When You’re Expecting. What to Expect follows strict reporting guidelines and uses only credible sources, such as peer-reviewed studies, academic research institutions and highly respected health organizations. Learn how we keep our content accurate and up-to-date by reading our medical review and editorial policy.
Blood Tests Used To Diagnose Diabetes
We will explain below the different blood tests that could be used to diagnose your diabetes. Your doctor will ask you about any symptoms you have and will then decide which type of blood test to use.
Having blood tests doesn’t need to be worrying, theyre straightforward and shouldnt take very long. Depending on the test you have you may be required to fast beforehand. If you do need to fast, a healthcare professional will let you know in advance.
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Random Blood Sugar Test
This measures your blood sugar at the time youre tested. You can take this test at any time and dont need to fast first. A blood sugar level of 200 mg/dL or higher indicates you have diabetes.
|140 mg/dL or below||N/A|
*Results for gestational diabetes can differ. Ask your health care provider what your results mean if youre being tested for gestational diabetes.Source: American Diabetes Association
If your doctor thinks you have type 1 diabetes, your blood may also tested for autoantibodies that are often present in type 1 diabetes but not in type 2 diabetes. You may have your urine tested for ketones , which also indicate type 1 diabetes instead of type 2 diabetes.
Is There Anything Else I Need To Know About Fasting Before A Blood Test
Be sure to talk to your health care provider if you have any questions or concerns about fasting.
You should talk to your provider before taking any lab test. Most tests don’t require fasting or other special preparations. For others, you may need to avoid certain foods, medicines, or activities. Taking the right steps before testing helps ensure your results will be accurate.
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How Can You Prepare Your Child To Fast Before A Blood Test
It can be difficult when your child requires any kind of test, including a blood test. However, there are ways you can help prepare yourself and your child ahead of time.
Ways to prepare your child for a blood test include:
- Explain things to them in advance.
- Stay positive, as you may feel more anxious than your child. Try to stay upbeat to keep them calm.
- Bring a distraction, such as their favorite toy.
- Ensure they are well hydrated before their blood draw.
- Let them look if they want to. Your instinct may be to cover their eyes, but this can increase their anxiety.
- Lend a hand. You may be asked to hold your child to provide comfort and help them stay secure.
- Bring a snack. If they are fasting, your child might be grateful to have a snack ready when the blood draw is complete.
How Long To Fast
Generally, you should fast for eight to 12 hours before lab work that requires it. Fasting for a blood sugar test, which is included in the basic metabolic panel, is generally eight to 12 hours.
You can always clarify how long to fast with your healthcare provider. If you are unsure, aim for 12 hours of fasting. For example, if you schedule your test for first thing in the morning, you should generally not eat anything after dinnertime the night before.
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Can I Skip Taking Glucose Tests
Yes, you can decline a glucose screening or test, but opting out is not recommended. Since most women with gestational diabetes don’t have any symptoms, getting tested may be the only way to find out if you have the condition.
Gestational diabetes puts you and your baby at risk of complications. Detecting gestational diabetes allows you to work with your provider on managing and reducing those risks so you can enjoy a healthy pregnancy.
Can You Drink Coffee If Youre Fasting Before A Blood Test
Even if you drink it black, coffee can interfere with blood test results. Thats because it contains caffeine and soluble plant matter, which might skew your test results.
Coffee is also a diuretic, which means that it will increase how much you pee. This can have a dehydrating effect. The less hydrated you are, the harder it can be for the nurse or other medical professional whos doing your blood test to find a vein. This can make the blood test harder or more stressful for you.
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What Are The Usual Treatments For Diabetes
For type 2 diabetes, which is the most common type of diabetes, losing excess weight, eating a healthy diet that is high in fiber and restricted in carbohydrates, and getting regular amounts of exercise may be enough to lower your blood glucose levels. In many cases, however, medications may be necessary to achieve the desired glucose level. With type 1 diabetes , insulin injections several times a day are necessary. See the article on Diabetes for more on treatment.
Is It Ok To Drink Water Before A Blood Test
Its fine to drink water before a blood test, unless youre instructed otherwise by your doctor. This is different from some surgical procedures, which may require you to have a totally empty stomach.
Tap or bottled water are both OK, but leave the squeeze of lemon for another time. Seltzer and club soda are off-limits. Carbonated beverages, flavored or otherwise, shouldnt be consumed during a fast, and neither should any type of tea.
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Will The Glucose Tests Make Me Feel Sick
Some moms-to-be feel nauseated after drinking the glucose solution, and a few even throw up. It may help to eat something a few hours before the screening test. If you vomit soon after youâve gotten the drink down, youâll have to come back on another day and repeat the test.
Itâs actually more common for women to feel sick during the three-hour glucose tolerance test, because the solution for that test is twice as sweet or contains twice as much liquid as the one for the screening test, and you have to drink it after fasting.
What Is The Two
The two-hour glucose tolerance test is basically a shortened version of the three-hour tolerance test. If you get this test, you likely won’t do the screening test first, which is why the two-hour version is sometimes referred to as the “one-step” glucose tolerance test.
Overnight fast: Typically you’re instructed to eat a late meal the night before the test and then to eat or drink nothing after that, except for sips of water. The fasting period is usually 8 to 14 hours before the test, so you’ll want to schedule the test for first thing in the morning.
Here’s what to expect at the lab:
- First blood draw: When you arrive for the test, a blood sample is taken to measure your fasting blood glucose level.
- Sweet drink: Next, you’ll drink a very sweet drink, which usually contains 75 grams of glucose.
- Two more blood draws: Your blood will be drawn at one hour and two hours after the drink.
- Results: If any of your blood sugar readings are abnormal you will be diagnosed with gestational diabetes.
This chart shows the levels that the American Diabetes Association considers abnormal at each interval of the two-hour glucose tolerance test :
|2 hours||153 mg/dl or higher|
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Can I Eat And Drink Before Having A Blood Test
It depends on the type of blood test you’re having. The healthcare professional arranging your test will tell you if you need to do anything to prepare for it.
You can eat and drink as normal before some blood tests. But if you’re having a “fasting blood test”, you will be told not to eat or drink anything beforehand. You may also be told not to smoke before your test.
Why Do I Need A Glucose Tolerance Test
In pregnancy, women who will be offered a GTT will have been identified as having one of the following:
- A raised body mass index over 30kg/mÂ². BMI is a measurement of your weight in kilograms and your height in metres.
- A previous baby over 4.5kg .
- Confirmed gestational diabetes in a previous pregnancy.
- Family origin .
- First degree relative that has diabetes .
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Why The Test Is Performed
This test checks for gestational diabetes. Most pregnant women have a glucose screening test between 24 and 28 weeks of pregnancy. The test may be done earlier if you have a high glucose level in your urine during your routine prenatal visits, or if you have a high risk for diabetes.
Women who have a low risk for diabetes may not have the screening test. To be low-risk, all of these statements must be true:
- You have never had a test that showed your blood glucose was higher than normal.
- Your ethnic group has a low risk for diabetes.
- You do not have any first-degree relatives with diabetes.
- You are younger than 25 years old and have a normal weight.
- You have not had any bad outcomes during an earlier pregnancy.
Choose Healthy Carbohydrates Instead
Complex or unrefined carbohydrates such as whole grain breads and cereals, whole fresh fruits and even baked potatoes are absorbed more slowly into your bloodstream and are less likely to give you the large sugar jolts that can result in excess glucose filtering into your urine.
In fact, since complex carbohydrates contain more fiber, they actually slow the absorption of sugar into your bloodstream. Whats more, they provide lots of essential nutrients for pregnancy .
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How Long To Fast Before Glucose Test Pregnancy
How Long To Fast Before Glucose Test Pregnancy
The length of time you should fast before a glucose test during pregnancy depends on the type of glucose test you are having. For a fasting glucose test, you should fast for at least 8 hours before the test. For a glucose tolerance test, you should fast for at least 24 hours before the test.
How Is It Done
Youâll get the OGTT at your doctorâs office, a clinic, hospital, or lab. HereÃ¢s what happens:
- A nurse or doctor will take a blood sample from a vein in your arm to test your starting blood sugar level.
- Youâll then drink a mixture of glucose dissolved in water.
- Youâll get another blood glucose test 2 hours later.
During pregnancy, the test is shorter. Youâll drink a sweet liquid. Then youâll have a blood test about 60 minutes later.
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What Is Being Tested
This test measures the amount of glucose in your blood. Glucose is a simple sugar that provides energy for the body.
People with diabetes often monitor their own blood glucose at home. This is done using a finger-prick test and a special machine, rather than a blood sample taken from a vein.
You might have blood taken for a blood sugar level. You might or might not be asked to fast beforehand.
There is also a test called an oral glucose tolerance test, abbreviated as OGTT or GTT. For this test you fast, then have a blood sample taken, then drink glucose, then have a number of samples taken over a few hours.