Diabetes
Glucose Monitoring
Intepreting Postprandial Glucose Readings
ByMichelle Pugle
Updated on August 22, 2024
Medically reviewed byMichael Menna, DO
Fact checked byNick Blackmer
Blood sugar levels after eating can vary by age, but a reading below 140 milligrams per deciliter (mg/dL) is generally considered normal. In contrast, levels over 200 mg/dL or higher may suggest that you have diabetes.
Postprandial glucose is the name for the level of glucose (sugar) in your blood after eating, which tends to spike one hour after eating and return to normal within two hours.
There are different ways to measure this, including a two-hour postprandial glucose (PPG) test, an oral glucose challenge, and a device called a glucometer. These tests can either help diagnose diabetes or determine if you're taking the right amount of insulin with meals.
Meaning of Normal and Abnormal Blood Sugar After Eating
Glucose is your body's main source of energy, which you obtain from carbohydrates you eat. Insulin is the hormone that regulates this process and helps move glucose into cells for fuel. Any unused glucose is converted into a form called glycogen and stored in the liver.
Under normal circumstances, blood sugar levels rise after you eat and fall again as cells take up glucose. Within two hours of eating, your insulin and blood sugar levels should return to normal.
However, if blood sugar levels don't fall as much as they should, it could be a sign of type 2 diabetes or prediabetes.
On the other hand, if you have diabetes, high postprandial blood sugar may be a sign that you are not managing your condition or the condition is getting worse.
Different tests and tools are available to measure postprandial blood sugar. Some are used for diagnostic purposes, while others are used to manage and monitor diabetes.
Two-Hour Postprandial Glucose Test
A two-hour postprandial glucose (PPG) test is a simple blood test used to measure the amount of glucose in your blood after eating. It involves measuring your blood sugar before and after drinking a controlled amount of a sugary solution.
Why the Test Is Used
Also known as an oral glucose tolerance test (OGTT), the two-hour PPG can determine whether you have prediabetes, type 2 diabetes, or gestational diabetes (a form of the disease affecting roughly 10% of people with pregnancy).
The PPG test may be recommended if you have symptoms of diabetes, like:
- Frequent urination
- Unusual thirst
- Blurred vision
- Chronic fatigue
- Repeated infections
- Sores that heal slowly
How the Test Is Performed
The two-hour PPG test is performed after a minimum of eight hours of fasting. The test is relatively easy to perform and involves three simple steps:
- A blood test is taken to measure your blood sugar after fasting.
- You are given a syrupy solution to drink containing 75 grams of sugar.
- Two hours later, another blood test is taken to measure your blood sugar.
An abbreviated version of the test, called an oral glucose challenge, is used for gestational diabetes. The test, routinely done between weeks 24 and 28 weeks of pregnancy, also involves three steps:
- A blood test is taken to measure your blood sugar after fasting.
- You are given a syrupy solution to drink containing 50 grams of sugar.
- One hour later, another blood test is taken to measure your blood sugar.
What the Results Mean
The two-hour PPG and oral glucose challenge are both used for diagnostic purposes. The results are typically described in milligrams per deciliter (mg/dL) but are sometimes measured in millimoles per liter (mmol/L).
The interpretations can vary by lab but are generally described as follows:
| Test | Interpretation | Result |
|---|---|---|
| Two-hour PPG test | Normal | Less than 140 mg/dL (7.8 mmol/L) |
| Prediabetes | Between 140 and 199 mg/dL (7.8 and 11 mmol/L) | |
| Type 2 diabetes | 200 mg/dL (11.1 mmol/L) or higher | |
| Oral glucose challenge | Normal | Less than 140 mg/dL (7.8 mmol/L) |
| Prediabetes | Between 140 and 199 mg/dL (7.8 and 11 mmol/L) | |
| Gestational diabetes | 190 mg/dL (10.6 mmol/L) or higher |
If results are inconclusive or borderline, your healthcare provider may recommend a three-hour PPG in which you are provided three sugary solutions and your blood is tested four times. The results of the three-hour test are especially useful in diagnosing gestational diabetes.
Glucose Monitoring
A glucometer is a simple device used to monitor your blood glucose levels if you have type 1 diabetes, type 2 diabetes, or gestational diabetes.
Why the Test Is Used
A glucometer is a self-test commonly used in people with diabetes. It is especially useful if you have type 1 diabetes (the type in which the pancreas makes little or no insulin) or are taking insulin to control your blood sugar.
A glucometer can be used to:
- Check your blood sugar levels and overall control
- Determine if you are taking enough insulin with meals
- Check glucose levels in response toexerciseorstress
- Check glucose levels before bedtime to proactively treat high and low levels
How the Test Is Performed
Depending on your condition, you may need to monitor your blood sugar as few as two times a day to as much as 10 times a day.
Testing should be done two hours after a meal. This information can help you and your provider assess if you need to change your insulin or medication doses.
This may include testing yourself:
- When waking up
- Before and after meals and snacks
- Before and after exercise
- If you have symptoms of low blood sugar (hypoglycemia)
- If you have symptoms of high blood sugar (hyperglycemia)
- Before bedtimes (and sometimes in the middle of the night)
Most glucometers work by drawing a little blood from your finger, placing it on a test strip, and then placing the strip in the device to obtain a reading.
There are also continuous glucose monitors that provide real-time readings 24 hours a day and can alert you if your blood sugar is too high or too low.
What the Results Mean
Normal postprandial blood sugar levels vary based on the type of diabetes you have and whether or not you use insulin. Normal levels are currently described as follows, measured in milligrams per deciliter (mg/dL):
| Group | Normal reading |
|---|---|
| Adults without diabetes | Under 140 mg/dL two hours after eating |
| Adults with type 1 or 2 diabetes | Under 180 mg/dL two hours after eating |
| Adults with type 1 or 2 diabetes who take mealtime insulin | Under 180 mg/dL two hours after eating |
| Adults with type 1 or 2 diabetes not taking mealtime insulin | Under 140 mg/dL two hours after eating |
| Pregnant adults with gestational diabetes | Under 140 mg/dL one hour after eating, and 120 mg/dL two hours after eating |
| Pregnant adults with preexisting type 1 or 2 diabetes | Under 110 to 140 mg/dL one hour after eating, and under 100 to 120 mg/dL two hours after eating |
| Children and teens under 18 with type 1 or 2 diabetes | Under 200 mg/dL one hour after eating, and under 180 mg/dL two hours after eating |
Based on the results, you may need to take steps to bring down your blood sugar if they are high. This includes taking fast-acting insulin or exercising to burn off excess glucose.
If levels are too low, you may need to eat or drink 15 grams of a fast-acting carbohydrate, such as three or four glucose tablets, four or five hard candies, or a 1/2 cup of fruit juice.
What Is the Best Time to Check Blood Sugar?
Why Monitoring Blood Sugar Is Important
For people with diabetes, postprandial blood glucose monitoring along with fasting blood glucose monitoring—meaning your blood sugar levels when you haven’t eaten—are important parts of diabetes management.
If left uncontrolled, chronic high blood sugar levels can start to damage multiple organ systems, leading to complications like:
- Diabetic neuropathy (diabetic nerve damage)
- Diabetic nephropathy (diabetic kidney disease)
- Diabetic retinopathy (diabetic vision damage)
- Increased risk of heart attack and stroke
- Foot damage
- Skin and mouth infections
- Hearing loss
Blood glucose monitoring helps you determine the appropriate strategy for controlling your blood sugar and avoiding these complications. This not only includes the use of insulin and diabetes medications but also lifestyle choices like diet and the foods you eat.
Role of Diet and Exercise
If you have diabetes, foods with a high glycemic index (GI)—meaning those that are rapidly digested and cause your blood sugar to spike—may need to be limited or entirely avoided in favor of foods with a low GI.
Here are just a few examples to consider:
High GI Food to Avoid
White rice
White bread
Potatoes
Cornflakes
Beets
Puffed rice cakes
Watermelon
Ice cream
Low GI Food to Eat
Brown rice
Whole-grain bread
Sweet potato, squash
Steel cut oats
Broccoli
Tree nuts, peanuts
Apples, oranges
Low-fat yogurt
Similarly, getting a minimum of 150 minutes of moderate-intensity exercise each week can help you better manage your diabetes. Moderate-intensity exercises are those—like brisk walking, jogging, swimming, dancing, or cycling—where you can talk during the workout but not sing.
The American Diabetes Association recommends that you break up your 150-minute weekly target into increments, such as 50 minutes of exercise three times a week, 30 minutes five times a week, or 25 minutes six times a week. Avoid going longer than 48 hours between workouts to reap the optimal benefits.
When to See a Healthcare Provider
People experience diabetes in different ways, and some may not even realize they have it until complications develop. This is why you need to to act if you suspect you have diabetes as it can lead to serious health concerns likevision loss,kidney disease,andstroke if left untreated.
Some common and uncommon signs of diabetes include:
- Skin problems: Including wounds that won't heal, recurrent skin infection, white patches or sores in your mouth, and skin discoloration in the armpits or groin
- Changes in vision: Including blurred vision, increased floaters, chronic eye pain, and light sensitivity
- Digestive and urinary problems: Including increased hunger or thirst, frequent urination, trouble swallowing, and unintended weight loss
- Other health concerns: Including persistent fatigue and tingling or pins-and-needles sensations in the hands and feet
If you are being treated for diabetes and have difficulty managing your blood sugar, see your provider. You may need an adjustment in your medications or changes in your diet or lifestyle to achieve tighter control.
Summary
Postprandial blood sugar is the level of glucose in your blood after eating. It tends to spike one hour after eating and normalize one hour later.
Postprandial blood sugar can be measured with a postprandial glucose (PPG) test to determine if you have prediabetes (140 to 199 mg/dL), type 2 diabetes (200 mg/dL and over), or gestational diabetes (190 mg/dL and over).
Postprandial blood sugar can also be monitored in people with type 1, type 2, or gestational diabetes using a device called a glucometer. The self-test can determine whether you are taking enough insulin with meals or need an adjustment in your diet or medications.
Dangerous Blood Sugar Levels in Diabetes
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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Michelle Pugle
Michelle Pugle writes health articles for award-winning websites, as seen in Healthline, Verywell, Everyday Health, Psych Central, and Health.com. She has a Master's degree, undergraduate degrees in English and Sociology, a diploma in Holistic Herbal Therapy, and is trained in mental health first aid, anti-violence work, and peer support work.
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