If you’re living with type 2 diabetes (also known as diabetes mellitus), you understand how important it is to keep glucose (blood sugar) levels within a normal range. Even if you take all the right precautions, you’re still at risk of hypoglycemia (glucose levels dropping too low) or hyperglycemia (high glucose).

In severe cases, low or high blood sugar levels can become dangerous and even life-threatening. Knowing the differences between these two conditions can help you act quickly and get the treatment you need.

Monitoring Your Blood Sugar Levels

In type 2 diabetes, your cells are resistant to insulin — they have trouble using this hormone to take in glucose from your blood. As a result, your blood sugar levels rise over time. Your pancreas tries to make more insulin to compensate, but eventually, it can’t keep up. As a result, your blood sugar levels can fluctuate, even without you knowing it’s happening.

Regularly monitoring your blood sugar levels can help you keep them under better control. Depending on your type 2 diabetes, your doctor may recommend checking your blood sugar with a glucose meter once or twice a day. If your blood sugar is well controlled, you may need to check only a couple of times per week. Testing around mealtimes is the best way to find out which foods cause your blood sugar to spike.

If you have type 2 diabetes, your blood sugar levels are also affected by your diabetes treatment. You may take sulfonylureas that stimulate your pancreas to make more insulin, or you may inject insulin directly to help control your diabetes. These therapies can cause low blood sugar, leading to hypoglycemia symptoms.

When checking your blood glucose levels around mealtimes or to see how your medications are affecting you, it’s important to know what readings are too high or too low. Numbers to remember include:

• Normal blood sugar — 70 to 140 milligrams per deciliter (mg/dL) or 3.9 to 7.8 millimoles per liter (mmol/L)
• Hypoglycemia — Less than 70 mg/dL or 3.9 mmol/L
• Hyperglycemia — More than 180 mg/dL or 10 mmol/L

If you notice that your blood sugar levels are often outside of the normal range, or if you begin experiencing symptoms of hypoglycemia or hyperglycemia, it may be time to talk to your doctor. However, symptoms — and how they differ between the two conditions — may not always be obvious, so here are some important details to know.

1. Hypoglycemia May Make You Hungry

Your body sends signals to your brain, communicating what you need to stay healthy. When your blood sugar levels dip too low, it can be a sign that you’re running out of glucose to use as fuel. Your body stores extra glucose in your liver and releases it when you’re hungry, but you need to replenish these sugar stores by eating.

To raise your low blood glucose levels in a pinch, you can take glucose tablets or drink a glass of fruit juice or soda. You can also eat chocolate or bread for a quick dose of carbohydrates, but these foods may take longer to work.

2. Hyperglycemia Can Increase Thirst and Urination

When your pancreas can’t make enough insulin or you have insulin resistance, your blood sugar levels begin to climb. The only way your body can get rid of extra glucose — other than using it as fuel — is by excreting it in your urine. Your kidneys begin working overtime to clear out the excess sugar, along with any extra fluid in your body. You’ll begin urinating more frequently than usual, often a first sign of hyperglycemia.

You can quickly become dehydrated, which can cause extreme thirst and lead to dry mouth. The more fluids you drink to replenish what you body has lost, the more you continue to urinate.

3. Your Heart May Beat Faster During a Hypoglycemic Episode

Hypoglycemia pushes your body into survival mode to make sure your brain continues to get enough glucose for fuel. In response, your body releases adrenaline to raise your heart rate and constrict (narrow) your blood vessels. As a result, more blood is pulled away from your extremities and sent to your brain, keeping it fed with energy.

You’ve likely experienced an adrenaline rush before. Along with having a rapid, racing heartbeat, you may begin sweating or feeling shaky or dizzy as well.

4. Hyperglycemia May Affect Your Breathing

Left untreated, extremely high blood glucose levels can lead to a complication known as diabetic ketoacidosis (DKA). If your insulin levels are too low, your cells can’t use sugar to make energy. Instead, your body begins to break down fat, releasing ketones — a type of acid — that can accumulate to poisonous amounts. According to the American Diabetes Association, DKA is more common in people with type 1 diabetes, but it can also occur in those with type 2 diabetes.

Normally, your kidneys help filter out ketones and excrete them in your urine. However, in DKA, your body is making ketones faster than your kidneys can clear them. Your body tries to compensate by having you breathe out carbon dioxide and ketones through your lungs, which can lead to Kussmaul breathing, a form of rapid or labored breathing. Ketones have a fruity scent, so if you or someone around you notices that your breath smells fruity, you need to seek medical attention immediately.

5. Sudden Loss of Focus or Balance May Signal Hypoglycemia

Low blood sugar levels can affect your brain. Without the necessary energy to keep its cells fueled, your brain reduces its oxygen use. You may find it hard to concentrate or become confused. Your brain also controls coordination and balance, so you may also have trouble walking. These symptoms can appear suddenly, so it’s best to be prepared with glucose tablets or a sugary snack. (Hyperglycemia can eventually affect the brain, but the process is slower and doesn’t cause immediate symptoms.)

Symptoms of Hypoglycemia vs. Hyperglycemia

Here’s a roundup of major symptoms of low blood sugar and high blood sugar, some of which the conditions share.

What To Do If You Experience Hyperglycemia

If you’re at risk of hyperglycemia, it’s best to work with your doctor to create a treatment plan you can follow at home in case of an emergency. Taking steps to control your blood sugar early during a hyperglycemic episode can help prevent DKA and potential hospitalization.

Steps you can take to treat hyperglycemia at home include:

• Taking an appropriate dose of insulin — Insulin acts quickly to help your cells absorb glucose from your bloodstream, lowering your blood sugar.
• Drinking extra fluids — Rehydrating with plenty of water or sugar-free beverages can help dilute your blood sugar and make up for lost fluid from frequent urination.
• Replenishing your body with electrolytes — Low insulin levels can drain your body of sodium, potassium, and other electrolytes (minerals in body fluid) needed to keep your muscles, nerves, and heart functioning properly.

If you begin to notice signs of DKA or your blood sugar levels aren’t falling, you should head for the emergency room.You’ll be given IV insulin and fluids to get your levels back under control. You may have to stay at the hospital for observation for a few days.

Talk to Your Doctor

If you’d like more information about hypoglycemia or hyperglycemia symptoms and what to do if they occur, talk to your health care professional. They can help you make an emergency treatment plan or adjust your medications if you’re experiencing these symptoms.

Talk With Others Who Understand

DiabetesTeam is the online social network for people with diabetes and their loved ones. On DiabetesTeam, more than 127,000 members come together to ask questions, give advice, and share their stories with others who understand life with diabetes.

Have you experienced an episode of hypoglycemia or hyperglycemia? Do you have an emergency plan to follow if you notice symptoms? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.