Post-meal blood sugar testing, or postprandial testing, involves checking blood sugar levels 1-2 hours after eating a meal.
It’s used to determine the impact of a meal on blood sugar levels. It’s also helpful in gauging how effective a mealtime insulin dose is at regulation blood glucose.
People on insulin usually combine long-acting basal insulin and shorter-acting insulins to mimic the pancreas’ normal function.
Without diabetes, a functioning pancreas normally secretes a small amount of insulin constantly, as well as releasing a larger amount in response to the rise in blood sugar from eating.
Many people with diabetes, especially type 1 diabetes, take a short- or rapid-acting insulin at mealtimes. This helps to control the natural rise in blood sugar after eating.
These insulins work quickly and peak ineffectiveness within minutes to a couple of hours, which is why they are most safe and effective when taken with a meal. Their effectiveness can be gauged by checking postprandial glucose levels.
What do preprandial blood sugar levels show?
Pre and post meal testing allows you to see how your meal and, where relevant, your medication for that meal affects your blood glucose levels.
Postprandial blood sugar measurements are commonly taken two hours after you have eaten.
Pre-prandial and post-prandial means the same thing as before meal and after meal testing.
If blood sugar levels are high before breakfast, it often means that the person might need their medications adjusted to help improve their fasting blood sugar.
Many people are in a fasted state (no eating within the past eight hours or longer) when they wake up, so if the pre-breakfast blood sugar is high, it’s usually not because of a meal. Some exceptions to this include if the person woke up in the middle of the night to eat or if they work night shifts, so don’t eat at typical times.
Preprandial blood sugars give some insight as to how the previous meal impacted blood sugar levels. Because they are taken at different times throughout the day, preprandial blood sugar levels can also reveal normal fluctuations in insulin levels and insulin resistance.
For instance, if blood sugar levels two hours after eating breakfast were normal but pre-lunch blood sugars were high again, it might mean that the person is experiencing more insulin resistance around that time and needs to adjust their basal medications.
Insulin resistance is a term for the body, not responding to insulin as well as it should. Insulin is a hormone that helps reduce blood sugar levels by allowing the sugar to be taken in by cells to use as energy. Without enough insulin, blood sugar builds up in the bloodstream, unable to enter the cells where it’s needed. Chronic insulin resistance increases the risk of developing type 2 diabetes as well as gestational diabetes, which is diabetes occurring in pregnancy.
If preprandial blood sugar levels are high, it’s a good idea to evaluate the last meal, which was consumed. Keeping a food and blood sugar diary is a very useful tool to learn the impact different foods have on your blood sugar level.
For example, someone might notice that their pre-lunch blood sugar is lower when they eat a vegetable omelet for breakfast compared to when they eat a higher carbohydrate/sugar breakfast, such as waffles with a side of fruit.
If preprandial blood sugar levels are low (hypoglycemia), it’s most often due to too much insulin being administered earlier. Medication dosages should be adjusted in the case of chronic hypoglycemia. It can also be a sign that not enough carbohydrates were consumed, given how much insulin was injected, so diet changes may also be warranted.
What are recommended pre-meal blood sugar levels?
A blood sugar level less than 140 mg/dL (7.8 mmol/L) is normal. A reading of more than 200 mg/dL (11.1 mmol/L) after two hours indicates diabetes. A reading between 140 and 199 mg/dL (7.8 mmol/L and 11.0 mmol/L) indicates prediabetes.
According to the American Diabetes Association (ADA), the recommended pre-meal blood sugar range is between 80-130 mg/dL. The American Association of Clinical Endocrinologists (AADE) has more strict blood sugar goals than the ADA but doesn’t have a specific pre-meal blood sugar recommendation.
Instead, the AADE recommends that fasting blood sugars are below 110 mg/dL and blood sugars two hours after a meal are less than 140 mg/dL (compared to the ADA’s recommendation of less than 180 mg/dL 1-2 hours after a meal).
Blood sugar goals for women with gestational diabetes are the most strict, as a high blood glucose level during pregnancy can lead to adverse outcomes in the mother and baby. It’s recommended that women with gestational diabetes maintain blood sugar less than 95 mg/dL before meals.
How long does it take for blood sugar to stabilize after eating?
Blood sugar levels should stabilize about 1-2 hours after eating a meal, which is why post meal blood sugar guidelines fall within that range. Everyone is different, so the time it takes to stabilize depends on the individual as well as the type of meal eaten.
Eating a meal rich in fat can delay the rise in blood sugar because fat takes the longest to digest compared to carbohydrates and protein. A high-fat meal stays in the stomach longer, meaning the parts of the meal that raise blood sugar won’t be released into the bloodstream as quickly.
This can cause delayed high blood sugar (hyperglycemia), as well as potential hypoglycemia (low blood sugar level) if short or rapid-acting insulins are used. Studies have found that adding 35 grams of fat to a meal can significantly increase blood sugar levels at five hours post-meal.
Tips to regulate blood sugar levels
- Keep a blood sugar/food log: Identifying trends in blood sugar responses with different types of foods can help make adjustments to achieve desired blood sugar after eating. People might notice a blood sugar spike with specific foods and then make changes to their eating habits to improve their glycemic control. This can help you to set a blood sugar goal.
- Eating consistent, balanced meals: When you eat a balance of carbohydrates, protein, and fat (otherwise known as the Plate Method), blood sugar tends to rise more slowly and not drop quickly.
Foods rich in fiber are helpful for promoting stable blood sugars, such as whole grains, fruits, vegetables, legumes, nuts, and seeds. Foods with a high glycemic index, such as sugary foods, white bread and rice, can cause blood glucose to rise.
Having a good source of protein with carbohydrates is also good for promoting healthy blood sugar levels. Some protein sources include meat, eggs, fish, dairy products, legumes, nuts, and seeds. Eating protein with carbohydrates can also help reduce reactive hypoglycemia (low blood sugar after eating, especially carbohydrate-based foods) in people without diabetes.
- Exercise regularly: Being active helps lower both insulin resistance and blood sugars. Muscles take up sugar for energy, so doing a mix of cardiovascular exercises like walking as well as weight training (bodyweight exercises or lifting weights) is ideal. Increasing muscle mass can help reduce insulin resistance as well since muscle tissue takes up glucose regardless of how much insulin is present.
- Take medications as prescribed: It’s important for those with diabetes to take diabetes medications as prescribed. Skipping doses, or taking more than prescribed, can be detrimental. Never adjust diabetes medications on your own; always consult with a healthcare provider.
- Check blood glucose regularly: People who check their blood sugar regularly tend to have better-controlled blood sugar overall. Checking blood sugar levels after eating helps to monitor sugar trends and glucose spikes.
It can also help people identify how their lifestyle habits affect their blood sugar and make adjustments to achieve better blood sugar control. To achieve this, some people use a continuous glucose monitor. This is a small device that you wear just under your skin. It measures your glucose (sugar) levels continuously throughout the day and night, letting you see trends in your levels and alerts you to highs and lows.
- Practice good sleep hygiene: Poor sleeping habits and shift work have been associated with increased blood sugar levels. Lack of sleep or a disrupted circadian rhythm seems to interfere with the body’s insulin response, leading to insulin resistance. The National Sleep Foundation also recommends several things to improve sleep hygiene, such as:
- Limiting daytime naps
- Avoiding caffeine and other stimulants close to bedtime
- Exercising during the day
- Avoiding heavy, fatty, or spicy foods close to bedtime
- Being exposed to natural light during the day
- Establishing a relaxing bedtime routine
- Keeping the sleeping environment comfortable, e.g., temperature between 60-67 degrees, using white noise machines, etc.
- Manage stress: Some studies have suggested a link between stress and the increased risk of developing type 2 diabetes. Stress stimulates our body’s fight or flight response, resulting in increased blood sugar levels and insulin resistance. Stress can also lead to poor eating habits, low-quality sleep, and other aspects of reduced self-care, contributing to higher blood sugars. Finding ways to manage stress can help improve both mental and physical health.
- Watch your weight: Being at a higher weight (“overweight” or “obese” according to body mass index) is associated with an increased risk of insulin resistance. Studies have found that a 5% reduction in body weight in those considered overweight or obese significantly reduced their risk of developing type 2 diabetes. Losing weight can also help reduce high blood sugar levels in people with existing diabetes.
Normal blood sugar levels are important for promoting overall health and wellbeing. It’s important to keep your blood sugar levels in your target range as much as possible to help prevent or delay long-term, diabetic complications, such as heart disease, vision loss, and kidney disease.
Many things impact blood sugar levels, including diet, exercise, stress, medications, and more. A person’s eating habits have a major impact on blood sugar levels, so learning how different foods and drinks impact blood sugar can help with diabetes management.
Blood sugar levels before meals are called preprandial, and after meals are called postprandial. Checking blood sugar before meals give an idea of how the previous meal affects your glucose level. If preprandial blood sugars are low or high, it can be a sign that the diet and/or diabetes medicines need to be adjusted to help achieve ideal blood sugars.
Blood sugars can be regulated through lifestyle changes such as healthy eating, being active, managing stress, and practicing good sleep hygiene. Medications may also be adjusted to help regulate blood sugars and achieve target preprandial blood sugars.