Hyperglycemia vs. Hypoglycemia: Recognizing the Signs of High and Low Blood Sugar

17 Sep 2025 By Omar M. Ghanem, M.D.

Hyperglycemia vs. Hypoglycemia: Recognizing the Signs of High and Low Blood Sugar

Maintaining stable blood sugar levels is crucial for overall health, especially for individuals with diabetes. When these levels fluctuate beyond the normal range, it can lead to two distinct conditions: hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar). Understanding the differences between these conditions, recognizing their signs, and knowing how to respond appropriately can prevent serious health complications. Fasting Blood Glucose 101 Why This Simple Test Is So Important

Hyperglycemia occurs when there is too much glucose in the blood, often due to insufficient insulin, insulin resistance, overeating, or lack of physical activity. Conversely, hypoglycemia happens when blood glucose levels drop too low, typically caused by excessive insulin, skipped meals, or intense exercise. Both conditions can manifest with various symptoms, and chronic or severe episodes can have detrimental effects on the body.

What is Hyperglycemia (High Blood Sugar)?

Hyperglycemia refers to a condition where the blood glucose levels are higher than the target range. Generally, a blood sugar level above 130 mg/dL before a meal or above 180 mg/dL two hours after a meal is considered hyperglycemia. This condition can develop gradually over hours or days and, if left untreated, can lead to serious health issues.

Common Causes of Hyperglycemia:

Insufficient Insulin: In people with type 1 diabetes, the body does not produce insulin. In type 2 diabetes, the body may not produce enough insulin or may not use it effectively.
Insulin Resistance: Cells become resistant to insulin, requiring more insulin to achieve the same effect.
Dietary Factors: Consuming excessive carbohydrates, especially sugary drinks and processed foods, can lead to elevated blood sugar.
Inactivity: Lack of physical activity can reduce the body’s sensitivity to insulin.
Stress and Illness: Stress hormones and illness can raise blood sugar levels.
Medications: Certain medications, such as corticosteroids, can increase blood glucose levels.

Recognizing the Signs of Hyperglycemia:

Recognizing the early symptoms of hyperglycemia is crucial for timely intervention. Common signs include: - Frequent Urination: The kidneys try to eliminate excess glucose through urine. - Increased Thirst: Due to fluid loss from frequent urination. - Blurred Vision: High blood sugar can affect the lens of the eye. - Fatigue: Cells are unable to access glucose for energy. - Headaches: Fluctuations in blood sugar can cause headaches. Mastering Your Blood Sugar A Guide To The Glycemic Index Gi

Severe Hyperglycemia can lead to more serious symptoms such as: - Nausea and Vomiting: High blood sugar can upset the digestive system. - Shortness of Breath: Especially if ketoacidosis develops (more on this below). - Dry Mouth: Indicating dehydration. - Weakness: Severe lack of energy. - Confusion: Brain function is impaired by high glucose levels. - Abdominal Pain: Associated with ketoacidosis.

Complications of Untreated Hyperglycemia:

If hyperglycemia is left unmanaged, it can lead to several serious complications, including:

Diabetic Ketoacidosis (DKA): A life-threatening condition primarily occurring in type 1 diabetes, where the body produces ketones (acids) due to insufficient insulin. Symptoms include rapid breathing, fruity-smelling breath, and loss of consciousness.
Hyperosmolar Hyperglycemic State (HHS): More common in type 2 diabetes, characterized by extremely high blood sugar and dehydration, leading to confusion, seizures, and coma.
Long-Term Complications: Chronic hyperglycemia can damage blood vessels and nerves, leading to cardiovascular disease, kidney disease (nephropathy), nerve damage (neuropathy), eye damage (retinopathy), and poor wound healing.

Table: Hyperglycemia - Causes, Symptoms, and Complications

| Feature | Description | |--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | Causes | Insufficient insulin, insulin resistance, overeating, inactivity, stress, illness, certain medications. | | Symptoms | Frequent urination, increased thirst, blurred vision, fatigue, headaches, nausea, shortness of breath, dry mouth, weakness, confusion, abdominal pain (in severe cases). | | Complications | Diabetic Ketoacidosis (DKA), Hyperosmolar Hyperglycemic State (HHS), cardiovascular disease, kidney disease, nerve damage, eye damage, poor wound healing. |

What is Hypoglycemia (Low Blood Sugar)?

Hypoglycemia occurs when blood glucose levels drop below the normal range, typically defined as below 70 mg/dL. This condition is especially concerning for individuals with diabetes who are taking insulin or certain oral medications that stimulate insulin production. Hypoglycemia can develop rapidly and requires immediate attention to prevent severe consequences.

Common Causes of Hypoglycemia:

Excessive Insulin: Taking too much insulin can lead to a rapid drop in blood sugar.
Skipped or Delayed Meals: Not eating enough or skipping meals can cause blood sugar to drop, particularly when taking insulin or other diabetes medications.
Intense Exercise: Physical activity can lower blood sugar levels, especially if it is prolonged or strenuous.
Alcohol Consumption: Alcohol can interfere with the liver’s ability to release glucose into the bloodstream.
Certain Medications: Some non-diabetes medications can lower blood sugar as a side effect.
Kidney or Liver Problems: These organs play a role in regulating blood sugar, and their dysfunction can lead to hypoglycemia.

Recognizing the Signs of Hypoglycemia:

Early recognition of hypoglycemia symptoms is critical to prevent progression to severe stages. Common signs include: - Shakiness: The body's stress response can cause tremors. - Sweating: Another sign of the body's stress response. - Dizziness: Low blood sugar can affect brain function. - Hunger: The body signals the need for glucose. - Irritability or Confusion: Brain cells are sensitive to low glucose levels. - Rapid Heartbeat: The body attempts to compensate for low glucose.

Severe Hypoglycemia can result in more serious symptoms: - Loss of Coordination: Neurological function is impaired. - Difficulty Concentrating: Cognitive function is compromised. - Slurred Speech: Similar to intoxication. - Seizures: Severe lack of glucose can cause seizures. - Loss of Consciousness: A critical state requiring immediate intervention. - Coma: Prolonged severe hypoglycemia can lead to coma. Fasting Blood Glucose What Your Results Mean For Your Long Term Health

Complications of Untreated Hypoglycemia:

Untreated hypoglycemia can lead to significant health risks, particularly:

Seizures: Insufficient glucose supply to the brain can trigger seizures.
Loss of Consciousness: Severe hypoglycemia can cause individuals to pass out.
Brain Damage: Prolonged or recurrent severe hypoglycemia can lead to irreversible brain damage.
Coma: A prolonged state of unconsciousness, requiring immediate medical attention.
Death: In extreme cases, severe and prolonged hypoglycemia can be fatal.

Table: Hypoglycemia - Causes, Symptoms, and Complications

| Feature | Description | |--------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------| | Causes | Excessive insulin, skipped meals, intense exercise, alcohol consumption, certain medications, kidney or liver problems. | | Symptoms | Shakiness, sweating, dizziness, hunger, irritability, confusion, rapid heartbeat, loss of coordination, difficulty concentrating, slurred speech. | | Complications | Seizures, loss of consciousness, brain damage, coma, death. |

Immediate Actions to Take

For Hyperglycemia:

Check Blood Sugar Levels: Use a glucose meter to confirm the high blood sugar reading.
Drink Water: Stay hydrated to help flush out excess glucose.
Administer Insulin: If you take insulin, follow your doctor's instructions for correction doses.
Engage in Light Exercise: Exercise can help lower blood sugar, but avoid strenuous activity if ketones are present.
Monitor for Ketones: If blood sugar is consistently high, check for ketones using a urine or blood ketone test. If ketones are present, seek medical attention immediately.
Adjust Diet: Avoid sugary drinks and high-carbohydrate foods.

For Hypoglycemia:

Check Blood Sugar Levels: Verify that blood sugar is below 70 mg/dL.
Consume Fast-Acting Carbohydrates: Eat or drink 15-20 grams of fast-acting carbohydrates, such as:
4 ounces of juice or regular soda
1 tablespoon of honey or sugar
Glucose tablets or gel
Recheck Blood Sugar: After 15 minutes, recheck blood sugar levels. If still low, repeat the carbohydrate intake.
Eat a Snack or Meal: Once blood sugar is above 70 mg/dL, eat a snack or meal that contains both carbohydrates and protein to stabilize blood sugar.
Emergency Glucagon: If the person is unconscious or unable to swallow, administer glucagon (if available) and call for emergency medical help immediately.

Prevention Strategies

Preventing Hyperglycemia:

Follow a Healthy Diet: Choose whole grains, lean proteins, and plenty of fruits and vegetables.
Regular Exercise: Engage in regular physical activity to improve insulin sensitivity.
Medication Management: Take prescribed medications as directed and monitor blood sugar levels regularly.
Stress Management: Practice stress-reduction techniques like meditation, yoga, or deep breathing exercises.
Frequent Monitoring: Regularly check blood glucose levels to identify and address issues promptly.

Preventing Hypoglycemia:

Meal Planning: Eat regular, balanced meals and snacks to avoid blood sugar drops.
Medication Timing: Coordinate insulin or diabetes medication doses with meal times.
Exercise Precautions: Monitor blood sugar levels before, during, and after exercise, and adjust insulin or carbohydrate intake as needed.
Carry Fast-Acting Carbohydrates: Always have a source of fast-acting carbohydrates on hand for emergencies.
Alcohol Awareness: Drink alcohol in moderation and always with food.
Diabetes Education: Understand how different factors affect blood sugar and learn to adjust your treatment plan accordingly.

How to Monitor Your Blood Sugar Effectively

Effective blood sugar monitoring is essential for managing both hyperglycemia and hypoglycemia. Regular monitoring allows you to understand how different factors, such as food, exercise, and medications, affect your blood sugar levels. Here are the best practices:

Choose the Right Monitoring Device:
- Blood Glucose Meter (BGM): A standard device that requires a small blood sample, usually from a finger prick.
- Continuous Glucose Monitor (CGM): A device that continuously tracks glucose levels via a small sensor inserted under the skin.
Know Your Target Range:
- Consult your healthcare provider to determine your target blood sugar ranges, considering factors such as age, overall health, and diabetes type.
Establish a Regular Monitoring Schedule:
- People on Insulin: Test multiple times a day, including before meals, two hours after meals, at bedtime, and before/during/after exercise.
- People on Oral Medications: May need to test less frequently, but still regularly. Your doctor can advise on the frequency based on your medication and health status.
- When to Test More Frequently: During illness, stress, changes in medication, or if you experience symptoms of hypo- or hyperglycemia.
Proper Testing Technique:
- BGM:
  - Wash and dry your hands.
  - Insert a test strip into the meter.
  - Prick your finger with the lancet.
  - Apply the blood sample to the test strip.
  - Record the reading in a logbook or app.
- CGM:
  - Follow the manufacturer's instructions for sensor insertion.
  - Ensure the sensor is properly calibrated (if required).
  - Monitor your glucose levels via the device's display or paired app.
Review Your Results with Your Healthcare Provider:
- Bring your monitoring logs or CGM data to your appointments.
- Discuss any patterns or trends with your doctor.
- Make necessary adjustments to your treatment plan based on these discussions.
Troubleshooting Tips:
- Meter Errors: Ensure your meter and test strips are within their expiration dates. Clean the meter regularly.
- Inaccurate Readings: Check that the code on the test strip matches the meter. Make sure you apply enough blood to the test strip.
- CGM Calibration Issues: Follow the manufacturer's guidelines for calibration. If you suspect inaccurate readings, confirm with a BGM test.

Practical Example: Blood Sugar Monitoring Schedules

| Monitoring Goal | Frequency | | ---------------------------------------- | ---------------------------------------------------------------------------------------- | | Insulin Users – Intensive Management | Before meals, 2 hours post-meal, bedtime, before exercise, during exercise (if needed) | | Insulin Users – Basic Management | Fasting, before dinner, and bedtime | | Oral Medication Users – Well Controlled | Once or twice daily at varying times | | Before and After Exercise | Just before, during (for prolonged activities), and after exercise |

Conclusion

Distinguishing between hyperglycemia and hypoglycemia is vital for individuals with diabetes and those at risk. Early recognition of symptoms and appropriate management strategies can prevent serious health complications. Regular blood sugar monitoring, a healthy lifestyle, and close collaboration with healthcare providers are essential for maintaining optimal blood sugar levels and overall well-being. Knowing when and how to act in response to both high and low blood sugar can make a significant difference in managing your health effectively.