What Are the Signs of High and Low Blood Sugar?

One of the challenges of managing diabetes is maintaining consistent blood sugar (glucose) levels. Even with diligence, some situations can cause high blood sugar, or hyperglycemia, while others can bring on low blood sugar, or hypoglycemia.

After all, it’s not just carbohydrate intake that influences the amount of glucose coursing through your bloodstream when you have type 2 diabetes. Emotional stress and certain medications can increase your blood sugar levels, and a boost in activity can cause it to drop, says Megan O’Neill, CDCES, a medical science liaison for diabetes care at Abbott healthcare company in Monterey, California. Sometimes, people experience a spike in their blood sugar early in the morning due to the “dawn phenomenon,” a temporary surge of hormones that occurs as the body prepares to wake, according to the Cleveland Clinic.

“For people with diabetes, managing blood glucose levels is especially important,” O’Neill says. “Levels that are too low or high can result in complications that affect your kidneys, heart, and vision, reduce your quality of life, require expensive interventions, or even be fatal.”

RELATED: 5 Strategies to Help Avoid Diabetes Complications

The more prepared you are to spot the signs of both high and low levels, the better able you’ll be to quickly and easily bring them back within a desired range and stay healthy.

What’s the right range for you? The answer is slightly different for everyone, and your doctor can help you pinpoint yours. The American Diabetes Association (ADA) generally recommends trying to stay within these blood sugar targets:

• Between 80 and 130 milligrams per deciliter (mg/dL) before meals
• Less than 180 mg/dL two hours after meals

The first step to staying in these ranges, and course-correcting high and low blood sugar levels along the way, is to monitor your blood sugar levels with a glucose meter.

Clinical guidelines recommend that anyone taking insulin test their glucose at least four times per day and as many as 12 times per day. Those who are pregnant or have difficulty maintaining healthy blood sugar levels also need to test their blood sugar more often. Factors that increase the ideal testing frequency include the type of insulin, past levels of glucose control, and symptoms, O’Neill says. Some people with diabetes can benefit from continuous glucose monitoring, a device that allows you to get readings without finger pricks every five minutes, she says.

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About High Blood Sugar (Hyperglycemia)

High glucose levels occur when the body doesn’t have enough insulin or can’t properly use the insulin it has to shuttle glucose from the bloodstream to the body’s muscles, organs, and tissues for fuel, O’Neill says. As a result, the amount of sugar in the blood builds up.

Hyperglycemia typically happens when you consume more carbohydrates or bigger portions of food than usual, if you don’t take enough insulin or other diabetes medication as prescribed, and if you decrease your levels of physical activity, she says. Heightened stress levels can also increase blood sugar levels. Non-diabetes-related medications that are known to raise blood sugar levels include steroids, beta blockers, birth control pills, and many mental health medications, she explains.

Signs of high blood sugar include frequent urination, fatigue, dry or itchy skin, feeling thirsty, more frequent infections, and eating more food but not gaining as much weight as usual, says Athena Philis-Tsimikas, MD, the corporate vice president for the Scripps Whittier Diabetes Institute in La Jolla, California.

High blood sugar levels can cause these symptoms through various mechanisms, according to the Mayo Clinic. For example, high blood sugar levels damage blood vessels and nerves throughout the body. They can also deprive organs of energy and can cause fluid to accumulate in the eyes. And in an attempt to get your blood sugar to a healthier level, your body will often increase urine output.

A blood sugar reading above 180 milligrams per deciliter (mg/dL) is considered above normal and can bring on these symptoms, although it’s possible to have high blood sugar without any symptoms, Dr. Philis-Tsimikas says.

A reading above 300 mg/dL can be dangerous, according to the University of Michigan, which recommends immediately informing your doctor if you have two or more readings of 300 mg/dL in a row. In severe cases, very high blood sugar levels (well above 300 mg/dL) can result in coma. If you experience mental confusion, nausea, or dizziness, proceed to the emergency room.

Ways to treat high blood sugar include:

• Take your medications as directed. Missing doses or taking insulin or other diabetes-managing medications at incorrect times can lead to large fluctuations in blood sugar levels up or down, O’Neill says. Apps such as Medisafe, which is free to download on the App Store and on Google Play, can help you stay on top of your medication regimen. The top-rated app allows you to plug your meds into your calendar and set reminders so you never miss a dose.
• Eat carbohydrates in moderation. The ADA recommends an individualized carb count for everyone with diabetes. Higher intakes can result in hyperglycemia and lower intakes in hypoglycemia. Count carbs by using an app such as the Carb Manager keto diet app, which is top rated and free to download on the App Store and Google Play. It’s not just for those on the ketogenic diet; with the free version, you can record food, track your carb and calorie intake, monitor weight loss, and log workouts.
• Exercise regularly with your doctor’s guidance. Exercise can lower blood sugar in the short term by using glucose for fuel. It can also help you manage your blood sugar over the long term by increasing insulin health, O’Neill says. Plenty of exercise apps and free online resources exist; work with your CDCES to come up with an individualized exercise plan.

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About Low Blood Sugar (Hypoglycemia)

Low blood sugar levels happen when there’s too little glucose left in the bloodstream to continue supplying fuel to your organs, muscles, and tissues. It most often occurs when you don’t eat enough food, especially carb-containing foods, given your blood-sugar-lowering medications and physical activity levels, O’Neill says. Levels can decrease gradually or suddenly.

When the amount of glucose in the bloodstream drops to too-low levels, the body reacts by releasing epinephrine, also called adrenaline or the “fight or flight” hormone. Epinephrine revs your heart rate and can cause sweating, shaking, anxiety, and irritability. If not enough glucose is able to reach the brain, the result may be difficulty concentrating, confused thinking, and slurred speech. In extreme cases, a lack of glucose within the brain can lead to seizures, coma, and even death, she says.

People with low glucose levels (lower than 70 mg/dL) can use the ADA’s “15-15 Rule,” which advises people consume 15 g of carbs, wait 15 minutes, and check their levels again. If the number is still low, repeat until reaching at least 70 mg/dL. It’s recommended that you check glucose with a traditional glucometer, not a continuous glucose monitor, given the lag time of the latter.

You can find 15 g of carbs in:

• 1 slice of bread
• 1 small piece of fresh fruit
• ? cup of yogurt
• ½ to 1 cup of juice, skim milk, or regular soda
• Three to four hard candies (such as Jolly Rancher or Werther's Original)
• Glucose tablets (such as ReliOn and TRUEplus) as indicated on the label
• Glucose gel (such as Glutose 15 and Insta-Glucose) as indicated on the label

Once your glucose levels are back to normal, the ADA suggests going ahead and eating your next scheduled meal or snack, which will help prevent levels from dropping again.

But if your symptoms don’t stop, call your doctor or seek medical attention. If you experience more than two blood sugar readings below 70 mg/dL in a week, notify your doctor and go over your treatment plan.

RELATED: 10 Warning Signs of Low Blood Sugar

A Few Final Notes on Keeping Blood Sugar Stable

Taking an active, intentional approach to your blood sugar levels is crucial to your quality of life and overall health, O’Neill says. Avoiding too-high or too-low blood sugar levels will help you avoid adverse symptoms and health complications, and staying within your target range can enable you to feel your best and do whatever you want to do in life, she says.

Test your blood sugar regularly, listen to your body, and don’t ever hesitate to reach out to your doctor.

Additional reporting by Karen Appold.