- Diabetes affects the body’s ability to move sugar out of the bloodstream and into cells.
- Eating too much sugar when you have diabetes increases blood sugar and may cause headaches, blurred vision and more.
- If you’re managing diabetes, be mindful of portion sizes of sugary foods and pair them with sources of fiber, protein and healthy fats.
Diabetes and prediabetes are conditions that affect many Americans. In fact, according to the Centers for Disease Control and Prevention, about 38 million adults and children in the United States have diabetes, with millions more who meet the criteria but haven’t been formally diagnosed.
When it comes to managing diabetes, there’s a lot of noise and misinformation about what you should and should not eat. One day a headline tells you to avoid sugar altogether, and the next it’s OK to eat only certain sugars. Believe me, even as a dietitian I know how confusing this can be.
That’s why we asked certified diabetes educators and registered dietitians to explain what happens to your body when you eat sugar if you have diabetes and share strategies for enjoying sweet treats while managing blood sugar levels.
Understanding Sugar and Diabetes
Sugar is a type of carbohydrate found in food. In addition to providing sweetness, it’s a source of energy, contributing 4 calories per gram. Sugar is found in plants and can also be made artificially in a lab. When talking about sugar in foods, it’s often divided into two categories:
- Natural sugars: These sugars are naturally present in the food itself and are not added by the manufacturer. For example, milk is naturally sweet thanks to a type of sugar called lactose, and unsweetened applesauce contains fructose, a sugar found in apples.
- Added sugars: Sugar that’s added to a food during processing or manufacturing is considered an added sugar. Common examples of added sugar include dextrose, sucrose, cane sugar, honey, maple syrup and concentrated forms of fruit and vegetables. For example, granola bars are often sweetened with honey or cane sugar.
Both natural and added sugars are carbohydrates and can affect your blood sugar levels. Whether you’re munching on an apple or a cookie, your body will break those sugar molecules down into glucose. The main difference is that natural sugar sources contain additional nutrients, like fiber, vitamins and minerals, that support your overall health.
How Sugar Affects Blood Glucose Levels
During digestion, sugar is broken down into glucose and released into the bloodstream. In healthy individuals without diabetes, the body responds by releasing insulin—a hormone that’s responsible for transporting glucose from the bloodstream into cells, effectively lowering blood sugar levels.
However, in the case of diabetes, the body’s ability to regulate blood sugar is affected. “When sugar is consumed, the person with diabetes either does not have enough insulin to transport the sugar into their cells for energy or their cells are resistant to insulin, forcing the sugar to remain in the bloodstream instead of in the cells for energy, resulting in elevated blood sugar levels,” explains New Jersey-based dietitian Erin Palinski-Wade, CDCES, author of 2 Day Diabetes Diet and creator of The Blood Sugar Fix.
Hyperglycemia 101
Over time, having frequently elevated blood sugar levels results in a condition known as hyperglycemia, or high blood sugars. Left untreated, hyperglycemia can lead to a host of symptoms and conditions that warrant medical care, including nerve damage, retinopathy, cardiovascular disease and more.
For people with undiagnosed diabetes, hyperglycemia is when fasting blood sugar levels are greater than 125 mg/dL or when blood sugar levels are over 180 mg/dL within two hours after their last meal. For reference, a “normal” blood sugar level in people without diabetes is less than 99 mg/dL fasting and less than 139 mg/dL after a two-hour glucose tolerance test.
For people with diabetes, hyperglycemia is usually considered a blood sugar level greater than 180 mg/dL up to two hours after eating, though this may vary by individual.
Potential signs of hyperglycemia include:
- Frequent urination
- Headaches
- Blurred vision
- Increased thirst
- Fatigue
- Poor wound healing
- Weight loss
- Skin infections
According to Virginia-based dietitian Jill Weisenberger, M.S., CDCES, CHWC, FAND, creator of The Prediabetes Meal Planning Crash Course, the best way to know whether your blood sugars are too high is by measuring your levels just before eating and again two hours later.
What Sugar Does to Your Body If You Have Diabetes
“It’s normal and desirable for blood sugar levels to rise after eating foods with sugar or other carbohydrates. In someone without diabetes, blood sugar stays in a healthy range. Someone with diabetes could have blood sugar rises that stay in the healthy range or go into levels that can cause problems now or sometime down the road,” says Weisenberger.
Here’s a closer look at how sugar can affect your body if you have diabetes.
You May Experience High Blood Sugar Levels
Because diabetes affects the body’s ability to efficiently move glucose from the bloodstream and into cells, eating sugar can cause blood sugar levels to rise higher or for longer than in someone without diabetes.
If you’re taking diabetes medications, like fast-acting insulin, your blood sugar level should return to a normal range within an appropriate time frame, assuming your medication is dosed correctly. However, if you eat a large amount of sugar or your medication dose or prescription isn’t quite right for your needs, you may have prolonged high blood sugar levels that can cause other health issues, which we’ll mention later.
You May Experience Difficulty Concentrating & Headaches
Glucose is the main fuel source for your brain. When glucose is just hanging around in the bloodstream instead of being transported into cells, your brain isn’t getting the energy it needs to function properly. As a result, you may find it hard to concentrate or experience headaches. Oftentimes, Weisenberger notes, patients aren’t aware that their concentration troubles or headaches are related to high blood sugars, since these are common symptoms of a variety of conditions.
You May Experience Fatigue, Increased Thirst & Frequent Urination
Excess glucose circulating in your blood can cause your kidneys to become overwhelmed. In healthy individuals, the kidneys play a key role in maintaining steady blood sugar levels thanks to an intricate filtration system. However, when blood sugar levels are too high, this system can get overwhelmed, causing glucose to spill into the urine. This causes more water to be drawn into the urine, altering the body’s hydration status. As a result, you may feel thirstier or need to pee more often.
Palinski-Wade notes that patients who have consumed “a large amount of added sugar with little to no protein, fat or fiber to slow the absorption down may find a spike in blood sugar which can lead to fatigue, increased thirst and increased urination.”
You May Experience Blurred Vision
Ever noticed blurry vision after eating a high-sugar meal? Weisenberger explains that this temporary change in vision is due to fluid changes that occur when blood sugar levels are elevated. Thankfully, correcting blood sugar levels quickly can return your vision to its usual state. However, over time, poorly controlled blood sugar levels can cause irreversible damage to the eyes, known as diabetic retinopathy.
You May Increase Your Risk for More Serious Health Conditions
Occasional high blood sugar levels can have short-term consequences, like headaches, fatigue, blurred vision, increased thirst and increased urination. However, over time, consistently elevated blood sugar levels can increase your risk for more serious health conditions, including nerve damage, heart disease, impaired eyesight, kidney disease and more.
“Over the long term, high blood sugar causes a host of chronic problems. When there’s an excess of sugar in the blood, some of that sugar will attach itself to various cells, affecting nerves, blood vessels and more. Think about where blood travels—everywhere in the body—so long-term damage can occur [anywhere] throughout the body,” says Weisenberger.
Strategies to Enjoy Sugar If You Have Diabetes
While it can seem like sugar is the enemy, our experts agree that this is far from true. People with diabetes can certainly enjoy sugar. The key is being mindful of how these foods fit into your overall treatment plan. Here are a few expert strategies to keep in mind if you have diabetes.
- Focus on a balanced diet with appropriate macronutrients. “With diabetes, the amount of carbohydrate (including sugar) consumed at one sitting matters most, so sugar should be spread out throughout the day and not consumed all at once. Having carbohydrates/sugar along with a good source of fiber, lean protein and healthy fat can help to promote more steady blood sugar levels,” says Palinski-Wade. Curious what this looks like? These 24 diabetes-friendly recipes can provide some inspiration!
- Maintain a regular eating schedule. Following a consistent eating schedule can make it easier to manage blood sugar levels and maintain a balanced diet. While fasting or skipping meals might be tempting from a weight-loss perspective, these habits are generally not recommended for people with diabetes, especially if you’re taking medication to manage your condition.
- Stay hydrated. “Drinking water to stay hydrated can also help to promote healthy blood sugar levels,” says Palinski-Wade. Focus on drinking zero- or low-sugar beverages, like plain or sparkling water, to keep the effect on your blood sugar levels to a minimum.
- Limit added sugars. The 2020–2025 Dietary Guidelines for Americans recommends limiting added sugar to no more than 10% of total daily calories. This amount is for everyone, not just those with diabetes. “When it comes to sweet treats, limit the amount. Think miniature brownies or an individual chocolate truffle, not a handful or a double scoop of ice cream. Sit down and love the heck out of it and forget the silly notion of cheating. Think treat, not cheat,” says Weisenberger.
- Manage stress levels. Having high levels of cortisol can wreak havoc on your blood sugar levels. Whether you enjoy journaling, yoga or therapy, it’s important to find ways to manage stress that you can do regularly.
- Get moving. When it comes to managing blood sugar, exercise is key. Even a short walk can make a meaningful difference in your blood sugar levels, especially after mealtime.
- Work with an expert. Registered dietitians and certified diabetes educators are invaluable resources when you have diabetes. By taking into account your medical history and lifestyle, they can develop a personalized treatment plan to help you manage your condition effectively.
Related: You Just Found Out You Have Type 2 Diabetes—Here Are 4 Things a Diabetes Educator Recommends Doing First
The Bottom Line
If you have diabetes, being aware of how sugar affects your body is crucial for managing your condition. Because diabetes affects the body’s ability to transport glucose into cells, eating sugar can cause increases in blood sugar levels, thirst and urination. It may also make it harder to concentrate or cause temporary changes in vision. The good news is just because you have diabetes doesn’t mean sugar is off the table.
When eating sugar-containing foods, nutrition experts recommend being mindful of portion sizes, limiting added sugars and incorporating them into an overall balanced meal to minimize blood sugar spikes. Whether you’re newly diagnosed or have had diabetes for years, working with a certified diabetes educator can help you create a meal plan that helps you achieve your blood sugar goals while still enjoying foods you love.
Frequently Asked Questions
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What happens to your body when your sugar stays high?
Elevated blood sugar levels can cause headaches, difficulty concentrating, blurred vision, increased thirst and increased urination. Long-term elevated blood sugar levels, also known as uncontrolled diabetes, can lead to more serious issues, like nerve damage, cardiovascular problems, kidney disease and eye damage.
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What brings down blood sugar immediately?
Both Palinski-Wade and Weisenberger agree that insulin is one of the best tools for lowering blood sugar levels. Weisenberger says, “If you take insulin for diabetes, you may need to adjust your dose. Sometimes, people who don’t use insulin to manage their diabetes may need it for a day or so. We see this when someone with diabetes is sick or injured, which often causes steep rises in blood sugar levels.”
Physical activity can also help lower blood sugar levels. “Without medication, movement can help to lower blood sugar levels quickly; however, strenuous exercise or exercising when ketones are present may further elevate blood sugar levels, so you should always speak to your physician first on the best strategy for you and your individual needs on lowering blood sugar levels,” says Palinski-Wade.
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Can people with diabetes eat sugar?
Yes, all foods can fit in a diabetes-friendly diet. While it’s best to prioritize minimally processed foods, like fruits, vegetables, lean proteins and healthy fats, Weisenberger agrees that people with diabetes can still enjoy sugary foods. “Remember the total amount of carbohydrate you eat is the greatest predictor of how high your blood sugar will go after eating. Simply count the sugar as part of your carbohydrate allotment for that meal or snack,” she adds.
