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Living with diabetes means learning to understand your blood glucose (blood sugar). Over time, you may begin to notice trends and patterns that can help you manage your condition more effectively. Checking your blood sugar regularly can reveal these patterns and help you identify what may lead to hyperglycemia (high blood sugar levels).
Eating — or skipping a meal — is one of many factors that can affect your blood sugar. That’s why your doctor may recommend checking your blood glucose before and after meals. In this article, we’ll cover how food affects your blood sugar, how different types of foods can have different effects, and when to talk with your doctor about your blood sugar levels.
Your body gets its glucose from the foods and drinks you consume, so it makes sense that eating affects your blood sugar. Your brain and body rely on glucose as a source of energy, so it’s something your body needs to function.
People living with diabetes are at risk of having too much or too little glucose (called hypoglycemia). Both can cause short-term health problems and may contribute to diabetes complications in the long term.
Foods and beverages aren’t the only factors influencing your blood sugar, but your eating habits can affect your blood sugar in a few ways.
Eating naturally raises blood sugar, but eating too much in one sitting can lead to hyperglycemia. Eating too many calories — just like missing a dose of insulin — can cause your blood sugar to spike.
A member of DiabetesTeam offered a helpful tip for avoiding overeating and preventing a blood sugar spike. “Portion control. I plate all my food on a 7-inch plate before eating,” they said.
Not eating enough can have the opposite effect. If you eat too few calories or skip an entire meal, your blood sugar can drop. Some people might attempt to lose weight or control high blood sugar by severely restricting their calorie intake, but doing so can destabilize blood sugar and increase the risk of hypoglycemia.
Your blood sugar responds to what you eat — and the way it responds depends on the type and amount of nutrients in your meals and snacks. Knowing how different foods affect your glucose levels can help you make choices that support your health.
If you find that your eating habits are making it harder to manage your blood sugar, talk with your healthcare provider or a registered dietitian. They may recommend diabetes-friendly recipes and cooking substitutions to help keep your blood sugar in your target range.
Carbohydrates (or carbs) are a type of macronutrient, which is a nutrient your body needs in large amounts to function. Your body breaks carbohydrates down to create glucose, so eating a lot of carbohydrates can raise your blood sugar. The effect on your blood sugar depends on the type of carbohydrate and how much you eat.
Simple carbs are carbohydrates with a simple chemical structure, which means your body can break them down quickly and easily. This means they’re more likely to cause a spike in your blood sugar. After the spike, your blood sugar can rapidly drop.
Sugars in the foods you eat are a type of simple carbohydrate. Some sugars are in natural foods like fresh fruit and dairy, while others are added to packaged and processed foods — even those that don’t taste especially sweet.
You’ll often find added sugars in:
Complex carbs are foods with a more elaborate chemical structure, so it takes your body longer to break them down. Eating them still raises your blood sugar, but it happens more slowly and isn’t followed by a dramatic drop. These carbs include important vitamins and minerals your body needs.
Fiber is a specific type of complex carbohydrate that helps with digestion. Since you can’t fully digest fiber, it helps you feel full for a long time.
You can find lots of fiber in foods like:
Unlike other carb types, fiber isn’t broken down into glucose. In fact, eating fiber helps regulate your blood sugar and prevent spikes. Because fiber plays such an important role in controlling your blood sugar, research suggests a low-fiber diet can increase your risk of being diagnosed with type 2 diabetes.
Protein is another essential macronutrient. When you don’t eat enough carbs, your body can use protein as an energy source instead. However, protein isn’t usually turned into glucose the way carbs are.
Your body digests protein slowly, which means it helps you feel full for longer. Protein has little direct impact on blood sugar levels, which makes it a helpful part of meals and snacks for people living with diabetes.
Fat is the third major macronutrient your body needs to function well. While fat has sometimes gotten a bad reputation, your body needs healthy fats to support hormone production, cell growth, and energy.
Like protein, your body doesn’t break down fat into glucose. However, eating healthy sources of fat — like avocado, nuts, seeds, and olive oil — can help slow down digestion and may reduce or delay spikes in blood sugar when eaten with carbohydrates.
That said, eating too much fat may contribute to insulin resistance. This is especially true for saturated and trans fats, which are found in foods like fatty cuts of red meat, butter, full-fat dairy, fried foods, and many packaged snacks and baked goods. Having insulin resistance means your body doesn’t respond to insulin as well, which can make it harder to manage blood sugar levels. Over time, insulin resistance can increase the risk of prediabetes or type 2 diabetes.
A DiabetesTeam member asked, “How can we slow the digestion of carbs and lower the post-meal glucose spike?”
Other members suggested eating protein or fat with their carbs to avoid a blood sugar spike. “I never eat a naked carb!” said one.
“Eat protein or fats with your carbs; it slows down digestion (healthy fats, though),” suggested another.
If you’re living with diabetes, your doctor might advise caution around alcohol. Drinking alcohol can lower your blood sugar, especially if you drink too much, drink without eating, or combine alcohol with certain diabetes medications.
Hypoglycemia can sometimes feel like being tipsy or drunk, with symptoms like dizziness, shakiness, or confusion. That’s why it can be dangerous to drink alcohol if you have trouble distinguishing the signs of low blood sugar.
Your liver usually helps regulate your blood sugar by storing extra carbs and releasing them between meals so your blood sugar stays somewhat constant. When you drink, your liver focuses on processing the alcohol instead. This may delay or reduce glucose release, increasing your risk of hypoglycemia, especially if you haven’t eaten.
Alcoholic drinks can also be high in calories and added sugars, which may affect your overall blood sugar management. If you enjoy the occasional beer, cocktail, or glass of wine, talk with your doctor about how to drink safely while living with diabetes.
Your doctor might recommend checking your blood sugar two hours after meals to see how eating affects your blood sugar and determine if you need any adjustments to your medication doses. You can check your blood sugar with a glucose meter and test strips, which require a quick finger prick for a small blood sample.
Some people use continuous glucose monitors (CGMs) to track their blood sugar automatically. These are wearable devices that use a sensor under your skin to read the amount of glucose in the fluid between your cells. Because CGMs can fail or give inaccurate information, your doctor might recommend still using a glucose meter and test strips to compare readings.
Most glucose meters and CGMs save your blood sugar test results, but keeping your own record of what you eat, when you eat, and your blood sugar readings can help you and your doctor see patterns in what affects your blood sugar most.
Talk to your doctor about when and how often to test your blood sugar. If you need to check your blood sugar daily, your doctor will probably tell you to do so before meals and before bed.
If your doctor recommends checking your blood glucose levels after eating, you should test them about two hours after the start of your meal. You should also test your blood sugar when you’re drinking alcohol, if you skip a meal, or if you feel like you’ve eaten too much.
After eating, your blood sugar should be less than 180 milligrams per deciliter (mg/dL) if you have diabetes. A reading higher than this could mean your blood sugar has spiked because you ate too much or too many simple carbs. It could also mean your treatment plan needs to be adjusted.
A blood sugar spike can cause symptoms like headaches, intense hunger, and irritability, but you can have high blood sugar without these symptoms. Most people living with diabetes notice high blood sugar symptoms only if their blood sugar is 250 mg/dL or higher, which is why blood glucose monitoring is important.
Keeping a journal of your meals and postmeal blood sugar readings can help you spot patterns. Over time, you may notice which foods lead to spikes and which help keep your blood sugar steady. This can empower you to make food choices that support your health and well-being.
Talk to your doctor if your blood sugar levels are too high or too low and you don’t know why. High or low blood sugar could mean you ate too much or too little, forgot to take your insulin, or took the wrong amount of insulin. There might be other factors at play, too, like stress, a lack of physical activity, or a condition like fatty liver disease.
DiabetesTeam is the social network for people with diabetes and their loved ones. On DiabetesTeam, members come together to ask questions, give advice, and share their stories with others who understand life with diabetes.
Do you measure your blood sugar levels after eating? Have you noticed how your energy changes after eating certain foods? Share your experience in the comments below, or start a conversation by posting on your Activities page.
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