It’s a fact of life that blood sugar fluctuates throughout the day. These ups and downs depend on a handful of factors, like when you wake up, what you eat, the medications you take, and how you manage stress. So, some variation is normal, to the point that you might not even notice it.
Ignoring blood sugar level changes altogether, though, means you’re ignoring a valuable marker of your health. Especially if you start to have new or unfamiliar symptoms like fatigue, thirst, or brain fog (to name a few). Learning these symptoms and their causes will give you the tools to better understand your own body, then take the right actions for better long-term metabolic health.
What is high blood glucose (aka “hyperglycemia”)?
To fully understand your blood glucose levels, it’s important to know: a) what values are actually considered high, and b) factors that can cause your elevated reading in the first place.
High blood glucose, also known as hyperglycemia, occurs when there is too much sugar in the bloodstream. Low blood sugar, or hypoglycemia, is the result of too little glucose in the bloodstream. Hyperglycemia usually occurs because your body doesn’t produce enough insulin or can’t properly use the available insulin to remove the glucose from the bloodstream.
Using milligrams of glucose per deciliter of blood (mg/dL) for measurement, high blood glucose readings after a meal indicating prediabetes can fall between 140 and 199 mg/dL. Levels reaching 200 mg/dL two hours after eating indicate you may already be insulin resistant or diabetic, though that diagnosis will need to come from your doctor. By comparison, the typical standard for normal glucose readings is to remain under 140 mg/dL throughout the day and under 100 mg/dL after eight hours of fasting.
A range of lifestyle factors, habits, and health conditions can cause high blood sugar. To debunk common hyperglycemia myths, review causes and symptoms, and discuss the best ways to address them, we spoke with two experts on high blood sugar levels: registered dietitian and For The Love of Diabetes creator Lori Zanini and registered dietitian nutritionist and diabetes management expert Mary Ellen Phipps.
Myths about high blood glucose
There are a handful of misconceptions surrounding high blood glucose. Some you might have heard before, some you may not even know are myths.
“Only diabetics get high glucose values”
While a high glucose value can indicate diabetes, nondiabetics can also have higher values than normal. When researchers studied people wearing a continuous glucose monitor who did not have a diabetes diagnosis, they found 93% of individuals reached glucose levels that are considered dangerous, with 10% spending over 2 hours per day in these dangerous levels. Traditional glucose measurements, like a single point in time blood glucose value, are unable to capture these abnormalities.
There are actually several causes of high blood sugar unrelated to diabetes that the CDC recognizes. These include certain foods, like artificial sweeteners and coffee. Other factors like stress can do it, too. If you live with an endocrine or pancreatic condition, had surgery recently, or are experiencing intense physical stress (say, from a sunburn), you may also see your glucose value rise.
“All carbs are created equal”
Phipps explains that, despite containing similar amounts of carbohydrates, one serving of pasta could have a hugely different effect on your blood glucose levels than one serving of rice. Likewise, that serving of pasta may have an entirely different effect on your blood glucose levels than your friends’ or even family members’. “We’re all unique,” Phipps says.
“I feel fine, so I don’t need to test my levels”
Zanini points out that having high blood glucose can come as a surprise to anyone. “It's possible they didn't notice any symptoms or were simply feeling 'more tired than usual,’” she says. “It's easy to attribute being tired to many other things. . .so this is why regular physicals with your healthcare provider are important.” The bottom line? Listen to your body, take note of symptoms as they arise, and consider monitoring your continuous glucose values.
“High glucose isn’t preventable”
According to the CDC, managing stress, staying active, and maintaining a balanced diet of fiber, protein, and fat, can help prevent the development of type 2 diabetes. You can also work with your doctor and a registered dietitian to devise a routine that's both preventative and sustainable.
“If my A1C is normal, my glucose is good”
An A1C result that’s below 5.7% is normal by the CDC’s standards, but having a result below that number isn’t the end of the story. Pregnancy, hemoglobin variants, anemia, liver disease, and certain medications can cause inaccurate A1C results.
Additionally, the A1C test is measuring your average glucose value over the past 3 months, but averages inherently do not capture highs and lows. So, you could have a normal average while also having abnormal glucose spikes. The A1C test should only supplement your regular blood sugar testing, not replace it completely.
Is having high blood glucose dangerous?
In short, it can be. Zanini says that untreated high blood glucose can lead to a wide range of health issues—some of the most common being chronic inflammation, heart disease, vision impairment, kidney disease, nerve damage, tooth decay, damaged blood vessels, and periodontal disease.
Having high blood glucose also puts us at risk of mitochondrial dysfunction and oxidative stress. The former is a condition in which mitochondria fail to produce energy for cells. The latter occurs when free radicals outnumber antioxidants in the body and increase the risk of disease and other damage.
Phipps notes to avoid these risks, catching high blood glucose early on, then taking action to treat it is extremely important.
What causes high blood glucose?
Experts are still learning about all the factors that can contribute to high blood glucose. With that in mind, these are the main known causes of high blood glucose.
Causes related to personal health
Insulin resistance
This condition occurs when the cells in your muscles, fat, and liver are unable to use the glucose in your bloodstream for energy. Your pancreas responds to this increase in glucose by producing more insulin to help your body process it. This excess amount of insulin in the bloodstream can eventually cause your body to lose insulin sensitivity or build resistance to it, leading to higher blood glucose levels.
Bodyweight and body fat
Research connects being overweight and having a higher body fat percentage with high blood glucose levels. In fact, a high body fat percentage might be a clearer indicator of high blood sugar and diabetes than weight or body mass index (BMI).
Other health conditions
Certain conditions could make you more likely to have high blood glucose. These include Cushing’s disease, polycystic ovarian syndrome (PCOS), and gestational diabetes. Blood glucose may also rise as the result of common illnesses like a head cold or the flu.
Hormonal changes
It isn’t just stress and sleep that can cause fluctuations in hormones. Illness, physical pain and trauma, menopause or menstruation can as well. In any of these instances, your blood glucose levels may rise due to the changes in your hormone levels.
Medications
Certain medications, including steroids and beta-blockers, can disrupt insulin’s effectiveness. Others, like second-generation antipsychotics and certain antibiotics, may contribute to high blood sugar. However, research to learn why this happens is ongoing.
Gut issues
A growing body of research links imbalances in the microbiota living in our guts to an inability to regulate glucose levels in the blood. This is sometimes due to antibiotic use or infection.
Genetics
A family history of high blood sugar and specific genes may increase a person’s chances of having high blood glucose and developing diabetes. People with African American, American Indian, Asian American, Pacific Islander, or Hispanic heritage may face greater risks.
Causes related to diet
Processed foods and sugar
Diet and how it relates to blood glucose values can vary immensely from person to person. But, research suggests that eating processed foods (particularly ones high in sugar and fat) can increase blood glucose.
Overeating or grazing
It’s a common belief that snacking throughout the day (a.k.a. “grazing”) will keep blood glucose levels steady. But, a 2013 study found that eating two large meals per day helped reduce blood glucose more effectively than six small meals per day. It’s also important to keep our meals to the right proportions, as overeating can raise blood glucose levels as well.
Dehydration
Some research has found a connection between low water intake and a greater risk of hyperglycemia. This is most likely because less water in the body means the concentration of glucose in the blood is higher.
Vitamin and mineral deficiencies
Research into this cause is ongoing. Yet, studies suggest diets lacking micronutrients like chromium, magnesium, or vitamin D may contribute to high blood glucose.
Causes related to lifestyle
Physical inactivity
Exercising prompts your body to burn more energy than usual, and, as a result, consume more glucose. Maintaining a low level of physical activity, on the other hand, means more glucose will remain in the bloodstream. This raises your overall blood glucose values in the process.
Exercise also makes our body more insulin sensitive, which means we will require less insulin for the rest of the day to control glucose levels.
Stress
Part of the body’s fight-or-flight response to stress is to produce additional glucose. Another facet of that response is an increase in the hormone cortisol. High cortisol can reduce the body’s sensitivity to insulin. As a result, blood glucose levels may also increase.
Poor sleep
A lack of quality sleep can inhibit how much insulin your body can release. It can also cause the production of cortisol, which makes it harder for insulin to work. When your body’s insulin cannot properly metabolize the glucose in your blood, the glucose remains there and your glucose levels rise.
10 main symptoms of high blood glucose
While an individual can have no noticeable symptoms and still have high blood glucose, knowing what kinds of symptoms tend to accompany high blood glucose helps us take the right action before things get worse. If for no other reason, keeping these markers of high blood glucose in mind can help you identify it more quickly in yourself.
The most common symptoms to be aware of are:
- Thirst
- Frequent urination
- Blurry vision
- Headaches and brain fog
- Increased cravings for carbs and sweets
- “Hanger”
- Poor energy levels or midday crashes
- Fatigue
- Unintentional weight loss
- Slow-healing cuts
How to diagnose high blood glucose
Doctors use four main tests to gauge patients’ blood glucose levels:
1. Fasting blood glucose test
Conducted after fasting for eight hours; a reading of 100 mg/dL or more is considered high or a sign of prediabetes, while a reading of at least 126 mg/dL indicates type 2 diabetes. However, for optimal health, we recommend aiming for a fasting glucose value below 90 mg/dL.
2. Oral glucose tolerance test
Conducted after fasting for eight hours, drinking a high-sugar glucose solution, and waiting two more hours; a reading of at least 140 mg/dL is considered a sign of prediabetes. A reading of 200 mg/dL or higher is type 2 diabetes. For optimal health, you want to aim for a two-hour glucose of 110 mg/dL or lower.
3. Random blood glucose test
Conducted at any time throughout the day; a reading of at least 200 mg/dL indicates type 2 diabetes.
4. A1c test
Conducted at any time throughout the day; a result below 5.7% is considered normal. A result greater than 5.7% is considered an indication of prediabetes, and a result of 6.5% or higher indicates type 2 diabetes.
How to treat high blood glucose
Zanini says high blood glucose treatment is a hyper-individualized process based on several personal details. These include age, pre-existing conditions, current medications, and current blood glucose value. But, several overarching lifestyle changes can help reduce high blood glucose.
Address a poor diet
Everyone can benefit from consuming a diet rich in whole foods. It’s further beneficial to minimize intake of processed foods, such as foods containing sugar, flour, and vegetable seed oil. While there is no “best” diet for everyone, this golden rule of nutrition can help any person get more from their meals.
Personalized nutrition makes room for your unique differences and takes your individuality into account. The best way to find your perfect diet is to test different approaches, experiment, work with a dietitian, and use data such as glucose monitoring to assess if something is working or not.
Maintain an active lifestyle
Take breaks during a sedentary workday, add a walk around the block to your morning routine, or try a new form of exercise. These activities bring great benefit in both the short and long term while helping reduce your overall stress. Including regular strength training and aerobic exercise will help to lower glucose values, as well.
Manage stress
Make stress-relieving practices like reframing your thoughts and soothing breathing exercises part of your daily routine. Doing so will reduce your overall stress and, in turn, help prevent spikes in cortisol.
Get adequate sleep
Getting good rest will help regulate your hormones and reduce unwanted spikes in your blood glucose levels.
Maintain a healthy weight
According to the American Diabetes Association, maintaining a healthy weight can help reduce your risk of developing high blood glucose and diabetes. If you’re working toward a healthy weight, the ADA recommends creating a sustainable routine you can stick with and focusing your efforts toward realistic goals.
Take medication as prescribed by your doctor
A doctor may prescribe anti-diabetes medication like metformin to help lower your blood glucose levels. If you’re at high risk of developing diabetes, taking this medication is crucial for lowering high glucose levels.
When should you see a doctor?
Your yearly doctor’s appointment is an excellent time to check in on your blood glucose levels. This is especially true if your age (over 45 years old), weight, or family history put you at higher risk for developing diabetes in general.
If you suspect you may have high blood glucose already, Zanini says that any changes in your health count as cause to see your doctor. Make an appointment to undergo the diagnostic tests listed above and to discuss treatment options with your provider. If you have high blood glucose and experience trouble breathing, vomiting, confusion, extremely high thirst, or other symptoms of diabetic ketoacidosis, seek medical attention right away. This condition occurs when your body burns fat too quickly and converts it into ketones, which make your blood acidic. It can be life-threatening if left untreated.
How to tell if your blood glucose levels are high?
When learning more about your overall health and how your body responds to your routines, staying informed about your blood glucose levels should be a top priority. The following glucose monitoring options can help you get a better picture of your health:
Blood tests
As previously described, your doctor can conduct a series of blood tests to determine your blood glucose level. These may include a fasting blood glucose test or a random blood glucose test.
Oral glucose tolerance test
Your doctor may also conduct an oral glucose tolerance test. This procedure requires you to fast for eight hours, drink a high-sugar solution, and wait two more hours before your doctor tests your blood. From that test, they can identify your blood glucose level.
Glucometer
Also known as a glucose meter, this device tests your blood glucose level with a finger prick. It can provide you with on-demand readings of your blood glucose levels.
Continuous Glucose Monitor (CGM)
This option measures your levels through a small, painless device on the back of your arm, keeping you updated on your blood glucose 24/7 and showing your responses to food, exercise, and other routines in real time.
Prioritizing sleep, nutrition, and regular doctor’s visits are key for maintaining a healthy blood glucose level. They're also highly effective preventative measures. Keeping track of new symptoms or changes in your health, like weight loss, fatigue, or increased thirst and urination is also important.
FAQs
Is 13 high for blood sugar? ›
Recommended Blood Sugar Targets
Before meals, your blood sugar should be: From 90 to 130 mg/dL (5.0 to 7.2 mmol/L) for adults. From 90 to 130 mg/dL (5.0 to 7.2 mmol/L) for children, 13 to 19 years old.
Physical or emotional stress triggers the release of hormones that can cause high blood sugar levels. Menstrual periods and menopause also cause changes in the hormones that affect blood sugar levels. Regular blood sugar testing can uncover patterns. This can help you and your health care team control your diabetes.
Is blood sugar level 14 high? ›If your blood sugar levels are consistently high (usually above 20 mmol/L in adults and above 14 mmol/L in children), you may have moderate to severe symptoms of high blood sugar.
Can you have high glucose and not be diabetic? ›Nondiabetic hyperglycemia means your blood glucose (sugar) level is high even though you do not have diabetes. Hyperglycemia may happen suddenly during a major illness or injury. Or, hyperglycemia may happen over a longer period and be caused by a chronic disease (diabetes type I or II).
What happens when blood glucose levels rise above normal? ›Having too much sugar in the blood for long periods of time can cause serious health problems if it's not treated. Hyperglycemia can damage the vessels that supply blood to vital organs, which can increase the risk of heart disease and stroke, kidney disease, vision problems, and nerve problems.
What is the normal blood sugar level for a 70 year old chart? ›Normal ranges of blood sugar levels are between 70 and 130 mg/dL before eating meals. The American Diabetes Association recommends seniors have blood glucose levels of less than 180 mg/dL two hours after eating.
Why is my blood sugar high in the morning when I haven't eaten anything? ›The dawn phenomenon
In the early hours of the morning, hormones, including cortisol and growth hormone, signal the liver to boost the production of glucose, which provides energy that helps you wake up. This triggers beta cells in the pancreas to release insulin in order to keep blood glucose levels in check.
Oatmeal offers a host of health benefits and can be a great go-to food for those with diabetes, as long as the portion is controlled. One cup of cooked oatmeal contains approximately 30 grams of carbs, which can fit into a healthy meal plan for people with diabetes.
Can anxiety raise blood sugar in non diabetics? ›Yes, emotions can affect your blood sugar. Anxiety, fear, even that happy feeling you had when you got that new job can be stressful sometimes. When we're stressed – whether it's physical stress or mental stress – our bodies produce hormones such as cortisol that can raise blood glucose even if we haven't eaten.
What is an unsafe blood sugar level? ›A level of blood sugar above 250 mg/dL or under 50 mg/dL is dangerous and requires medical emergency treatment. The optimal blood sugar level that you want to achieve is generally between 70 and 130 mg/dL.
What is a dangerously high blood sugar level? ›
If your blood sugar level goes above 600 milligrams per deciliter (mg/dL), or 33.3 millimoles per liter (mmol/L), the condition is called diabetic hyperosmolar syndrome.
Does high blood sugar make you tired? ›Fatigue is a common symptom of diabetes. It can result from high blood sugar levels and other diabetes complications. Some lifestyle changes can help a person manage diabetes fatigue.
Can something other than diabetes cause high blood sugar? ›Nondiabetic hyperglycemia means your blood glucose (sugar) level is high even though you do not have diabetes. Hyperglycemia may happen suddenly during a major illness or injury. Instead, hyperglycemia may happen over a longer period of time and be caused by a chronic disease.
What can cause false high blood sugar readings? ›However, various factors such as application errors, extreme environmental conditions, extreme hematocrit values, or medication interferences may potentially falsify blood glucose readings. Incorrect blood glucose readings may lead to treatment errors, for example, incorrect insulin dosing.
Does caffeine affect blood sugar? ›For most young, healthy adults, caffeine doesn't appear to noticeably affect blood sugar (glucose) levels, and having up to 400 milligrams a day appears to be safe.
What organ controls your blood sugar? ›The main function of the pancreas is to maintain healthy blood sugar levels. It is a large gland located behind the stomach. It produces insulin, glucagon, and other hormones. Diabetes occurs when the pancreas does not produce enough insulin or when the body does not use insulin properly (called insulin resistance).
What are the 10 signs of high blood sugar? ›- increased thirst and a dry mouth.
- needing to pee frequently.
- tiredness.
- blurred vision.
- unintentional weight loss.
- recurrent infections, such as thrush, bladder infections (cystitis) and skin infections.
5 Blood vessel damage can start at A1C levels above 7%. The risk of complications significantly increases at A1Cs above 9%.
What is a good A1C for seniors? ›For functionally independent older adults, the IDF recommends an A1C goal of 7–7.5%, whereas for functionally dependent, frail patients or patients with dementia, an A1C goal of 7–8% is recommended.
What is a normal A1C for a 60 year old woman? ›A normal A1C level is below 5.7%. Normal eAG is below 117 mg/dL or 6.5 mmol/L. If someone's A1C levels are higher than normal, they may have diabetes or prediabetes. Their doctor might order a repeat test to confirm this.
What is a good blood sugar level in the morning? ›
What should your blood sugar be when you wake up? Whenever possible, aim to keep your glucose levels in range between 70 and 130 mg/dL in the morning before you eat breakfast, and between 70 and 180 mg/dL at other times.
What is a dangerously high blood sugar level? ›If your blood sugar level goes above 600 milligrams per deciliter (mg/dL), or 33.3 millimoles per liter (mmol/L), the condition is called diabetic hyperosmolar syndrome.
Is 12 high for blood sugar level? ›Hyperglycemia, the term for expressing high blood sugar, has been defined by the World Health Organisation as: Blood glucose levels greater than 7.0 mmol/L (126 mg/dl) when fasting. Blood glucose levels greater than 11.0 mmol/L (200 mg/dl) 2 hours after meals.
What does a blood sugar level of 15 mean? ›If your blood sugar level is 15 mmol/l or more, you should check your blood or urine for ketones. If ketones are present, it is likely that you do not have enough insulin in your body. This means you may need to increase your dose or give yourself an extra dose.
At what sugar level should I go to the hospital? ›According to the University of Michigan, blood sugar levels of 300 mg/dL or more can be dangerous. They recommend calling a doctor if you have two readings in a row of 300 or more.
What foods can diabetics eat freely? ›- vegetables. nonstarchy: includes broccoli, carrots, greens, peppers, and tomatoes. ...
- fruits—includes oranges, melon, berries, apples, bananas, and grapes.
- grains—at least half of your grains for the day should be whole grains. ...
- protein. ...
- dairy—nonfat or low fat.
Drinking water regularly may rehydrate the blood, lower blood sugar levels, and reduce diabetes risk ( 20 , 21 ). Keep in mind that water and other zero-calorie drinks are best. Avoid sugar-sweetened options, as these can raise blood glucose, drive weight gain, and increase diabetes risk ( 22 , 23 ).
At what A1C level does damage start? ›5 Blood vessel damage can start at A1C levels above 7%. The risk of complications significantly increases at A1Cs above 9%.
Why is my blood sugar high in the morning when I haven't eaten anything? ›The dawn phenomenon
In the early hours of the morning, hormones, including cortisol and growth hormone, signal the liver to boost the production of glucose, which provides energy that helps you wake up. This triggers beta cells in the pancreas to release insulin in order to keep blood glucose levels in check.
A growing body of evidence suggests a relationship between mood and blood-sugar, or glycemic, highs and lows. Symptoms of poor glycemic regulation have been shown to closely mirror mental health symptoms, such as irritability, anxiety, and worry. This should come as no surprise, as the brain runs primarily on glucose.
What are the 10 signs of high blood sugar? ›
- increased thirst and a dry mouth.
- needing to pee frequently.
- tiredness.
- blurred vision.
- unintentional weight loss.
- recurrent infections, such as thrush, bladder infections (cystitis) and skin infections.
Increase Insulin
Increase your dose. Take a fast-acting type before meals to help with swings in blood sugar after you eat. Take a long-acting type once or twice a day to help give you smoother blood sugar control. Use an insulin pump, which may make it easier to manage your blood sugar levels.
Metformin lowers your blood sugar levels by improving the way your body handles insulin. It's usually prescribed for diabetes when diet and exercise alone have not been enough to control your blood sugar levels.
Is oatmeal good for diabetics? ›Oatmeal offers a host of health benefits and can be a great go-to food for those with diabetes, as long as the portion is controlled. One cup of cooked oatmeal contains approximately 30 grams of carbs, which can fit into a healthy meal plan for people with diabetes.
What are 3 signs of a diabetic emergency? ›- hunger.
- clammy skin.
- profuse sweating.
- drowsiness or confusion.
- weakness or feeling faint.
- sudden loss of responsiveness.
Apples are an excellent fruit to include in your diet if you have diabetes. Most dietary guidelines for people living with diabetes recommend a diet that includes fruits and vegetables (21). Fruits and vegetables are full of nutrients such as vitamins, minerals, fiber, and antioxidants.