Updated 14th April 2022

Why should you test your postprandial blood sugar?

Postprandial blood sugar — the level of sugar in your blood after you eat and drink — is an important indicator of metabolic and overall health. Monitoring your postprandial blood sugar levels can help you to understand your personal responses to the foods you eat. 

It’s normal for your blood sugar to rise after you eat and then fall again as the cells in your body take in the sugar from your blood to use for energy or to store for later.

But blood sugar that's consistently too high isn’t good for your body and can be a sign of type 2 diabetes. 

There are recommended target ranges for postprandial blood sugar for people living with diabetes.

But for those without the condition, the current postprandial blood sugar thresholds are designed for healthcare professionals making a diabetes diagnosis after consuming a special sugary drink. There are currently no targets for when you are eating your normal diet.

At ZOE, we run the largest scientific study of postprandial blood sugar and blood fat responses in the world, with over 15,000 participants so far. Part of our ongoing research is investigating postprandial target ranges for people without diabetes.

The ZOE at-home test analyzes your blood sugar after you eat, along with your blood fat levels and your gut health, all of which are important factors in your health. Together, we use these to recommend the best foods for your overall health and unique blood sugar responses. 

Take our free quiz to find out what ZOE can do for you.

What are normal and high levels of postprandial blood sugar?

Typically, blood sugar levels peak between 1 and 2 hours after eating, when the carbohydrates in your food have been broken down into glucose — or sugar — and this has entered your bloodstream. 

To test your postprandial blood sugar responses, healthcare professionals can use an oral glucose tolerance test (OGTT).

For this test, a healthcare professional measures your blood glucose before and 2 hours after you drink a special sweet drink that contains 75 grams of glucose. The results indicate the following:

  • A postprandial blood sugar measurement below 140 mg/dL (7.8 mmol/L) is considered normal.

  • If your levels are between 140 and 199 mg/dL (7.8 and 11 mmol/L), it indicates that you may have prediabetes.

  • A reading of 200 mg/dL ( 11.1 mmol/L) or higher suggests that you have diabetes, but your doctor may use more than one test to make a diagnosis.

These values are specific for the OGTT test and the high amounts of sugar in the drink that you consume as part of it. 

For adults who are living with diabetes, the American Diabetes Association recommend specific postprandial blood glucose target ranges to aim for during everyday life:

For people without diabetes, there aren’t any guidelines for postprandial blood sugar levels when eating their normal diet.

The thresholds that healthcare professionals use for making a diabetes diagnosis are specific to the OGTT test. 

Why is your postprandial blood sugar important?

Postprandial blood sugar levels are important for people both with and without diabetes.

For people with diabetes, postprandial blood sugar, along with fasting blood sugar — your levels when you haven’t eaten — is an important part of overall diabetes management. Consistently high levels could mean that your treatment plan may need to be adjusted. 

Left uncontrolled, elevated blood sugar can increase your risk of diabetes complications such as heart disease, kidney disease, stroke, blindness, and other health conditions.

If you don’t have diabetes, postprandial blood sugar measurements can give you clues about your metabolic health. 

If your levels remain high a couple of hours after you eat, it’s an indication that you may have insulin resistance, which is when your cells aren’t able to take in glucose from the blood as well. 

Check with a healthcare professional if you are concerned about your postprandial blood sugar levels, as they will be able to do a number of tests to establish if your blood sugar levels are within a healthy range. 

Gradual increases in blood sugar after you eat, followed by gradual drops, are a normal part of digestion and are nothing to be concerned with. 

However, if your blood sugar regularly spikes too high or stays high for too long, and dips below your baseline afterward, you could experience both immediate and long-term health effects.

In the short term, sharp increases and dips in blood sugar may result in:

  • Increased appetite: ZOE researchers found that people who experience drastic spikes and dips in blood sugar are more likely to feel hungry again sooner, and eat more calories throughout the day, than those who have more moderate changes.

  • Mood changes: One study linked large spikes in blood sugar to a 38% higher score for depression and a 55% higher score for overall mood disturbances.

  • Fatigue: A review of research involving over 1,200 participants found that spikes in blood sugar are associated with tiredness and feeling less alert within an hour after eating.

  • Inflammation: Studies suggest elevated postprandial blood sugar levels can promote increased short-term inflammation in your body, which can lead to serious health implications over time. 

In the long term, the effects of regularly high postprandial blood sugar can increase your risk of many metabolic diseases, such as:

  • Heart disease: Researchers have found that consistently high levels of postprandial blood sugar can increase your risk of developing heart disease, whether you have diabetes or not.

  • Type 2 diabetes: Blood sugar levels that are regularly too high can damage your body’s ability to regulate blood sugar even further, increasing your risk of developing type 2 diabetes.

  • Overweight: A diet that regularly leads to sharp spikes in blood sugar, often one that includes a lot of ultra-processed foods, has been associated with an increased risk of developing overweight.

  • Chronic inflammation: Repeated postprandial blood sugar spikes can increase your risk of diseases linked to unwanted inflammation in your body, including obesity, type 2 diabetes, heart disease, and stroke.

Who should test their postprandial blood sugar?

Understanding your postprandial blood sugar levels can be important for everyone, regardless of your current health.

If you regularly notice any of the above symptoms after a meal, testing your postprandial blood sugar responses could help identify problems early.

But even if you’re not experiencing symptoms, blood sugar responses to the same food can vary hugely between different people. That’s why anyone can benefit from a better understanding of their blood sugar responses.  

Our research shows that nutrition is personal, and the foods that will give you big blood sugar rises will be different from another person’s. 

With ZOE’s at-home test, you can learn about your personal blood sugar responses by using a sensor called a continuous glucose monitor. This important tool allows you to measure your blood sugar levels before and after meals to see how you respond to the typical foods you eat, as well as our carefully balanced test muffins.

We compare your results with those of thousands of other people who have eaten the same standardized muffins and give you an in-depth picture of your blood sugar responses.

But blood sugar levels are only one part of your metabolic health.

ZOE’s at-home test kit also looks at your blood fat levels and your gut microbiome. These are linked to your responses to foods, too, and your risk of developing metabolic diseases like heart disease, stroke, and type 2 diabetes.

Getting the full picture of your body’s unique responses to what you eat allows us to provide you with personalized recommendations for the foods that are best for you.

You can take our free quiz to find out more about how ZOE can help you.

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Summary

Postprandial blood sugar — the amount of sugar in your blood after you eat — is an important indicator of metabolic health. If your blood sugar is high on a regular basis, you may be at higher risk of long-term health conditions, such as heart disease, stroke, and type 2 diabetes.

Healthcare professionals can measure your postprandial blood sugar levels after you drink a special sweet drink to see if you have diabetes.

If you are living with the condition, there are recommended target ranges to aim for, but your doctor will be able to work with you to set the right target range for you.

For people without diabetes, there currently aren’t official target ranges to aim for during everyday life. But our scientists are currently studying this. 

ZOE’s at-home test kit can help you to understand how your blood sugar responds to different foods and food combinations. It also looks at your blood fat levels and the makeup of your gut microbiome. Together, we use these to recommend the best foods for your body.

Take a free quiz to learn how ZOE can help you with your health goals.

Sources

Blood sugar level ranges. (2022). https://www.diabetes.co.uk/diabetes_care/blood-sugar-level-ranges.html

Blood sugar levels during pregnancy. (2022). https://www.diabetes.co.uk/diabetes_care/blood-sugar-levels-during-pregnancy.html

Carbohydrates and blood sugar. (n.d.) https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar

Diabetes complications. (2019). https://medlineplus.gov/diabetescomplications.html

Diagnosis. (n.d.). https://www.diabetes.org/diabetes/a1c/diagnosis

Gestational diabetes (n.d.). https://www.diabetes.org/diabetes/gestational-diabetes

Glycemic targets: standards of medical care in diabetes. Diabetes Care. (2018). https://diabetesjournals.org/care/article/41/Supplement_1/S55/29783/6-Glycemic-Targets-Standards-of-Medical-Care-in

Importance of postprandial glucose in relation to A1C and cardiovascular disease. Clinical Diabetes. (2019). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6640888/

Subjective mood and energy levels of healthy weight and overweight/obese healthy adults on high- and low-glycemic load experimental diets. Appetite. (2016). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5154680/

Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood. Neuroscience & Biobehavioral Reviews. (2019). https://www.sciencedirect.com/science/article/abs/pii/S0149763418309175

The big picture: checking your blood sugar. (n.d.). https://www.diabetes.org/healthy-living/medication-treatments/blood-glucose-testing-and-control/checking-your-blood-sugar

What is diabetes? (2021). https://www.heart.org/en/health-topics/diabetes/about-diabetes

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