Why You Should Check Your Blood Sugar After Meals

Checking your blood glucose (sugar) levels at least once a day may be part of your overall plan for managing type 2 diabetes. But if you’re not testing after you eat, you’re likely missing the full picture.

"Postprandial glucose levels — meaning ‘sugar after the meal’ — give you and your care team more important information about how the body is able to manage glucose after a meal," explains endocrinologist Pratima Kumar, MD, an associate professor at the University of Texas at Austin. “It informs us if the blood glucose has returned to normal after the meal intake.”

Food and Blood Sugar

“Glucose levels begin to rise about 10 minutes after the start of a meal and peak two hours after a meal,” Dr. Kumar says. “The glucose levels [then] return to premeal levels within two to three hours.”

Why Postprandial Glucose Measurements Are Important

“In patients who achieve their premeal glucose targets but whose A1C remains above target, postprandial glucose monitoring and therapy is recommended,” Kumar says.

Postprandial Glucose Data Is Vital Feedback

Your postprandial blood sugar data can also help you troubleshoot your diabetes management in many different ways.

First and foremost, these measurements give you direct feedback on your diet. If you’re not measuring after meals, you don’t know which foods contribute the most to your high blood sugar levels. And though you already know that foods with lots of added sugars and refined starches should be avoided or limited, you may be surprised to see the effects of the other foods you eat.

The data can also help your doctors refine your treatment strategies. “By measuring postprandial glucose, we can determine whether dietary modifications or pre-meal bolus insulin are needed to reduce these spikes,” Kumar says.

Who Should Check Blood Sugar After Meals?

There are no one-size-fits-all recommendations for blood sugar monitoring with type 2 diabetes. Diabetes specialists will tell some of their patients to check their blood sugar several times a day, and others to check only every once in a while, depending on their health status and individual goals.

You should work with your care team to devise a testing regimen that fits your unique situation. If you’re already meeting your A1C targets, it may be unnecessary to test your blood sugar after every meal. But if you are trying to improve your diabetes control, postprandial glucose checks can provide you and your clinician extremely valuable information.

• Use insulin, especially rapid-acting insulin before meals
• Are pregnant
• Have been unable to achieve their glucose targets
• Have experienced hypoglycemia (low blood sugar)
• Have a risk of diabetic ketoacidosis (DKA)

Even if you don’t think you have an enhanced need to check postprandial glucose levels, performing these checks intermittently can help flesh out your understanding of your blood sugar health.

“Blood glucose levels vary at different times throughout the day over a period of weeks,” Kumar says. “Thus, it’s important to check your blood glucose at regular intervals to provide accurate information to your physician.”

Consider a Continuous Glucose Monitor (CGM)

If an old-school fingerstick blood sugar test is like a snapshot, the continuous glucose monitor (CGM) provides high-definition video. This device, which attaches to the upper arm, continually estimates your blood sugar level and sends data to a smartphone app all day and night.

A CGM provides a far more complete picture of how your blood sugar rises and falls after a meal. This continuous data reveals not only the peak glucose level but also how fast it shot up and how quickly it dropped, potentially catching hidden spikes that traditional testing misses.

This immediate, personalized feedback allows you to instantly see the impact of specific foods, exercise, and medication timing, enabling you to make precise adjustments to your diet (and insulin doses) for far better overall control.

In the United States, most insurers will reimburse CGMs for people with type 2 diabetes who use insulin. CGMs are also now available over the counter.

The Takeaway

• If you’re not checking your blood sugar levels after meals, you have an incomplete picture of your health and the success of your diabetes management.
• Consistently high postprandial glucose spikes can be particularly damaging, potentially increasing the risk of cardiovascular disease, even more than high fasting glucose levels.
• Monitoring post-meal blood sugar provides critical feedback for making dietary adjustments and can also inform other lifestyle changes, such as activity levels, to better control glucose spikes.