Hypoglycemia vs. Hyperglycemia

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Hypoglycemia and hyperglycemia refer to blood sugar levels that are too low or too high, respectively. A fasting blood sugar level below 70 milligrams per deciliter (mg/dL) is referred to as hypoglycemia, while a fasting blood sugar level over 130 mg/dL is called hyperglycemia.

Blood sugar changes, whether a dip or a spike, can cause symptoms and serious complications. These conditions are common in people with diabetes but can also be caused by other factors and occur in people without diabetes.

Person taking blood sugar on middle finger

Mntri Thiph Sr / EyeEm / Getty Images

Causes and Risk Factors

Hypoglycemia
  • Unbalanced diet

  • Skipping meals

  • Exercise

  • Medications

Hyperglycemia
  • Family history

  • Medications

  • Major illness

  • Smoking

  • Injury

Hyperglycemia Causes

Hyperglycemia occurs when there is too much sugar in the blood. This happens either when your body has too little insulin (the hormone that transports glucose into the blood) or if your body can't use insulin properly like in the case of type 2 diabetes.

The causes of hyperglycemia in people with diabetes include:

  • The dose of insulin or oral diabetes medication that you are taking is not enough.
  • The amount of carbohydrates you are taking in when eating or drinking is not balanced with the amount of insulin your body is able to make or the amount of insulin you inject.
  • You are less active than usual.
  • Physical stress from an illness, such as a cold, the flu, or an infection, is affecting you.
  • Stress from family conflicts, emotional problems, or school or work is affecting you.
  • You are taking steroids for another condition.
  • The dawn phenomenon (a surge of hormones the body produces every morning around 4 a.m.–5 a.m.) is affecting you.

Other possible causes of hyperglycemia include:

Hypoglycemia Causes

Hypoglycemia occurs when there is too much insulin in the body, resulting in low blood sugar levels. It is common in people with type 1 diabetes, and it can occur in people with type 2 diabetes taking insulin or certain medications. 

For people without diabetes, hypoglycemia is rare. Causes of hypoglycemia in people without diabetes can include:

  • Having prediabetes or being at risk for diabetes, which can lead to trouble making the right amount of insulin
  • Stomach surgery, which can make food pass too quickly into your small intestine
  • Rare enzyme deficiencies that make it hard for your body to break down food
  • Medicines, such as salicylates (such as aspirin), sulfa drugs (an antibiotic), pentamidine (to treat a serious kind of pneumonia), or quinine (to treat malaria)
  • Alcohol, especially with binge drinking
  • Serious illnesses, such as those affecting the liver, heart, or kidneys
  • Low levels of certain hormones, such as cortisol, growth hormone, glucagon, or epinephrine
  • Tumors, such as a tumor in the pancreas that makes insulin or a tumor that makes a similar hormone called IGF-II

For people with diabetes, accidentally injecting the wrong insulin type, too much insulin, or injecting directly into the muscle (instead of just under the skin) can cause low blood sugar.

Other causes of hypoglycemia in people with diabetes include:

  • Being more active than usual
  • Drinking alcohol without eating
  • Eating late or skipping meals
  • Not balancing meals by including fat, protein, and fiber
  • Not eating enough carbohydrates
  • Not timing insulin and carb intake correctly (for example, waiting too long to eat a meal after taking insulin for the meal)

Symptoms

Hyperglycemia
  • Fatigue

  • Vision changes

  • Excessive thirst

  • Fruity breath

  • Increased hunger

  • Nausea, vomiting

Hypoglycemia
  • Headache

  • Shaking

  • Sweating

  • Hunger

  • Fast heartbeat

Hyperglycemia Symptoms

While hyperglycemia symptoms can start small and insignificantly, the longer your blood sugar is high, the worse these symptoms can become. Typically, hyperglycemia starts with fatigue, headache, frequent urination, and increased thirst. Over time, symptoms can progress to nausea and vomiting, shortness of breath, and coma.

Recognizing the symptoms of high blood sugar and treating them early are key to avoiding serious complications.

Hypoglycemia Symptoms

Hypoglycemia symptoms also tend to start slowly and may not be recognized at first, but without treatment, symptoms tend to become more serious.

The common symptoms related to low blood sugar include shakiness, hunger, fast heart rate (tachycardia), and sweating. They also can include irritability, inability to concentrate, and dizziness.

If your blood sugar levels are dangerously low (below 54 mg/dL), severe symptoms can occur. These symptoms can include confusion, behavioral changes, slurred speech, clumsy movements, blurred vision, seizures, and loss of consciousness.

It should be noted that blood sugar levels may dip lower or rise higher than the normal range, but without accompanying symptoms, they won't be diagnosed as a hyperglycemic or hypoglycemic episode.

Treatment

Hyperglycemia
  • Fast-acting insulin

  • Regular exercise plan

  • Weight loss

  • Exercise

  • Surgery

  • Eating carbohydrates in moderation

Hypoglycemia
  • 15 grams of carbohydrate

  • Glucose tablets

  • Medications

  • Dietary changes

Hyperglycemia Treatments

For nonemergency episodes of hyperglycemia, a person can turn to fast-acting insulin to reduce blood sugar. Another quick way to lower blood sugar is with exercise.

Prevention should come first to ensure these spikes in blood sugar don't happen to begin with. Some ways to ensure that blood sugar stays level and doesn't go too high include following a regular exercise plan and eating a balanced diet. Maintaining a healthy weight, quitting smoking, and limiting alcohol intake can help prevent future hyperglycemic episodes.

Hypoglycemia Treatments

Hypoglycemia can usually be treated in a pinch with snacks or drinks you have on hand. The 15-15 rule states that you should raise your blood sugar gradually by first eating 15 grams of carbohydrate, waiting 15 minutes, and checking your blood sugar level. If your blood sugar is still below 70 mg/dL, repeat the steps until you feel better.

Glucagon can be used along with emergency treatment to manage low blood sugar. It comes in liquid form in a prefilled syringe or an auto-injector device for you to inject just under the skin. Glucagon is also available as a powder that can be mixed with a provided liquid to be injected into the skin, muscle, or vein.

After injecting glucagon, the patient should be turned onto their side to prevent choking if they vomit. Use glucagon injection exactly as directed. Do not inject it more often or inject more or less of it than prescribed by your healthcare provider.

To avoid low blood sugar symptoms and complications, discuss any changes and concerns with your healthcare provider. Some ways to avoid low blood sugar include keeping emergency medication or glucose tablets on hand, discussing your condition with loved ones, empowering them to assist you if needed, and wearing a medical identification card in case of an emergency.

If you don’t feel better after three tries of the 15-15 rule or if your symptoms get worse, call your healthcare provider or 911. Healthcare providers can use a medication called glucagon. They inject it with a needle or squirt it up your nose. 

Complications

Hyperglycemia
  • Eye damage

  • Kidney damage

  • Peripheral neuropathy (nerve damage outside the brain and spinal cord) and autonomic neuropathy (damage to nerves controlling involuntary bodily functions)

Hypoglycemia
  • Seizures

  • Loss of consciousness

  • Falls or accidents

  • Death

Hyperglycemia Complications

Complications of hyperglycemia can affect various body systems, from your eyes to your nerves. Additionally, ongoing high blood sugar can lead to worsening heart disease and peripheral arterial disease.

Treatment and outlook depend on the person's individual needs and circumstances. If hyperglycemia happens during pregnancy, it is considered serious since it can cause damage to the fetus and mother.

Pregnancy can change how the body regulates blood sugar levels. Gestational diabetes is a complication of pregnancy and should be closely monitored.

Parents of children experiencing high blood sugar should work closely with a healthcare provider. High blood sugar, especially when chronic, is a sign of starting for worsening diabetes.

Hypoglycemia Complications

Low blood sugar levels can lead to serious complications as well. The most common complications of severe hypoglycemia include seizures, loss of consciousness, and death. It should also be noted that people experiencing low blood sugar can fall or have accidents due to the shakiness and dizziness that the condition causes.

Summary

Hyperglycemia and hypoglycemia both can cause symptoms and serious complications if left untreated. While they can't be completely prevented, symptoms can be managed so you can get your blood sugar back to normal when they do occur.

A Word From Verywell

Blood sugar levels may be out of sight, out of mind for people without diabetes. However, it's still important to know the signs of hyperglycemia or hypoglycemia so you can take action or seek help immediately when symptoms start. Symptoms are treatable without medical attention most of the time, but if symptoms recur, aren't changing with treatment, or become severe, talk to your healthcare provider.

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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. MedlinePlus. Long-term complications of diabetes. Updated May 25, 2021.