Hyperglycemia vs. Hypoglycemia: Understanding Blood Sugar Extremes

Explore the essential differences, causes, symptoms, and treatments for hyperglycemia and hypoglycemia—including how to recognize and manage both blood sugar emergencies.

By Sneha Tete, Integrated MA, Certified Relationship Coach

Created on Sep 26, 2025

Explore the essential differences, causes, symptoms, and treatments for hyperglycemia and hypoglycemia—including how to recognize and manage both blood sugar emergencies.

Blood sugar, or glucose, is the body’s main source of fuel. For many people, blood glucose remains within a normal range, but for people with diabetes or certain medical conditions, there can be dangerous swings—low blood sugar (hypoglycemia) or high blood sugar (hyperglycemia). Understanding the differences, symptoms, causes, and treatments for each is essential for effective management and long-term health.

What Is the Difference Between Hyperglycemia and Hypoglycemia?

Hyperglycemia refers to blood sugar levels that are too high, while hypoglycemia refers to blood sugar levels that are too low.
These conditions are essentially opposites but both pose key risks if not addressed promptly.

	Hypoglycemia (Low)	Hyperglycemia (High)
Definition	Blood sugar less than 70 mg/dL	Blood sugar over 125 mg/dL fasting or over 180 mg/dL post-meal
Common in	People taking insulin or diabetes meds; rarely, those without diabetes	People with diabetes (type 1 and type 2)
Key Symptoms	Shakiness, dizziness, sweating, confusion, fast heartbeat	Increased thirst, frequent urination, fatigue, blurred vision
Risks	Seizures, loss of consciousness, coma	Serious complications, long-term organ damage

Understanding Blood Sugar and Insulin

Glucose is the main fuel for the body’s cells. Insulin is a hormone produced by the pancreas that enables glucose to enter cells, where it is used for energy. When this system fails—either from too little insulin, insulin resistance, or over-treatment with insulin—abnormal blood sugar levels can occur.

Type 1 diabetes: The body produces little or no insulin. People need lifelong insulin therapy.
Type 2 diabetes: The body doesn’t use insulin effectively (insulin resistance) and may not produce enough.

Normal and Target Blood Sugar Ranges

While blood sugar ranges may differ depending on guideline and health status, the following are commonly accepted targets:

Non-diabetic adults: 70–140 mg/dL
People with diabetes: 80–180 mg/dL (varies with individual goals)
Hypoglycemia threshold: <70 mg/dL
Hyperglycemia threshold: >180 mg/dL two hours after eating, >125 mg/dL fasting

What Is Hypoglycemia?

Hypoglycemia is a state of low blood sugar, most commonly defined as a blood glucose reading below 70 mg/dL on a glucometer or a continuous glucose monitor (CGM).

Causes of Hypoglycemia

Too much insulin or diabetes medication
Skipping or delaying meals
Excessive exercise without enough food intake
Alcohol consumption (especially without food)
Rarely, certain non-diabetes medications or health conditions (such as tumors, malnutrition, or adrenal insufficiency)

Symptoms of Hypoglycemia

Shakiness or trembling
Sweating
Heart palpitations or rapid heartbeat
Dizziness or light-headedness
Hunger
Fatigue or weakness
Headache
Confusion or irritability
Slurred speech
In severe cases: seizures, fainting, loss of consciousness

Treatment for Hypoglycemia

Follow the 15-15 rule: Eat 15 grams of fast-acting carbohydrates (such as glucose tablets, juice, or regular soda); wait 15 minutes and recheck blood sugar.
Repeat as needed until blood sugar returns to 70 mg/dL or higher.
For severe cases (unconsciousness), emergency glucagon injection may be necessary. Seek medical help immediately if a person cannot swallow or loses consciousness.

What Is Hyperglycemia?

Hyperglycemia describes high blood sugar, often defined as blood glucose levels exceeding 125 mg/dL fasting, or 180 mg/dL two hours after eating for people with diabetes. In non-diabetics, levels this high are unusual and may signal other health issues.

Causes of Hyperglycemia

Insufficient insulin or diabetes medications
Consuming excessive carbohydrates or sugary foods
Lack of physical activity
Physical or emotional stress
Illness or infection
Certain medications (like steroids)

Symptoms of Hyperglycemia

Increased thirst (polydipsia)
Frequent urination (polyuria)
Dry mouth and dehydration
Fatigue or weakness
Blurred vision
Headache
Nausea or vomiting
Confusion or difficulty concentrating
In severe cases: shortness of breath, fruity-smelling breath, or coma

Treatment for Hyperglycemia

Take extra insulin or prescribed diabetes medication as directed (after checking blood sugar and with guidance from your healthcare provider)
Increase physical activity
Hydrate by drinking water
If symptoms are severe or persist, seek medical attention
In some cases, hospitalization may be required due to risk of diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS)

Key Differences Between Hypoglycemia and Hyperglycemia

Origin: Hypoglycemia is often due to excess diabetes treatment or skipping meals, while hyperglycemia usually results from inadequate treatment or other physical stressors.
Frequency: Both can occur in people with diabetes; hypoglycemia is rare in those without, hyperglycemia can be the first sign of diabetes.
Symptoms: Hypoglycemia symptoms start suddenly and can escalate quickly; hyperglycemia often develops more slowly with subtler symptoms early on.
Short-term risk: Hypoglycemia can cause immediate harm (coma, death) if not treated fast; hyperglycemia’s short-term risks lie in severe elevations (“diabetic emergencies” like DKA or HHS).
Long-term risk: Repeated hyperglycemia causes chronic complications (eye, kidney, nerve, and heart damage); frequent hypoglycemia can blunt the body’s warning signs or increase cardiovascular risks.

Complications Associated with Blood Sugar Extremes

Hypoglycemia Complications

Seizures and loss of consciousness
Brain damage after prolonged, untreated hypoglycemia
Increased risk of injury (e.g., falls, car accidents)

Hyperglycemia Complications

Short-term: Diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic syndrome (HHS)—both are life-threatening
Long-term: Nerve damage (neuropathy), kidney failure, retinopathy (eye disease), heart attack, stroke, poor circulation leading to limb amputation

Who Is at Risk?

People with diabetes: Both hyper- and hypoglycemia can occur due to changes in medication, diet, activity, illness, or stress.
People without diabetes: Hypoglycemia is rare, but can result from certain medications, critical illnesses, hormonal deficiencies, alcohol abuse, or rare tumors. Hyperglycemia without diabetes is uncommon, but can occur with certain illnesses or as an early sign of developing diabetes.

Diagnosis and Monitoring

Blood sugar monitoring is key for both prevention and management.

Fingerstick testing (glucometer): Measures capillary blood glucose at home or in clinical settings.
Continuous glucose monitoring (CGM): Tracks glucose trends throughout the day and night, providing real-time alerts for dangerous highs or lows.
Laboratory blood tests: Used for formal diagnosis and monitoring (such as fasting plasma glucose, HbA1c for long-term averages).

Prevention Strategies

Preventing Hypoglycemia

Eat regular meals and snacks
Take diabetes medications as prescribed and never skip meals if on insulin or sulfonylureas
Monitor blood sugar more frequently during changes in routine, illness, or after exercise
Limit alcohol intake and never drink on an empty stomach

Preventing Hyperglycemia

Follow your diabetes care plan and check blood sugar regularly
Adhere to medication and insulin regimens
Moderate carbohydrate intake as needed
Stay active and maintain a healthy weight
Manage stress levels
Address illnesses promptly and follow sick-day rules

When to Seek Medical Attention

For hypoglycemia: If symptoms do not improve with treatment; if person becomes unconscious, call emergency medical services immediately.
For hyperglycemia: If blood sugar remains >250 mg/dL for several hours; if symptoms of DKA develop (nausea, vomiting, stomach pain, confusion, fruity breath, rapid breathing); seek urgent care.

Outlook and Living With Diabetes

People living with diabetes can minimize the risk of both hyperglycemia and hypoglycemia through education, consistent monitoring, medication management, and healthy lifestyle choices. Work closely with your healthcare provider to create a personalized plan and gain confidence in responding to symptoms before they become emergencies.

Frequently Asked Questions (FAQs)

Q: Can you have symptoms of high and low blood sugar at the same time?

A: It’s rare but possible for symptoms to overlap, such as fatigue, confusion, or headache, which can be present in both conditions. Monitoring blood sugar is essential to determine the actual problem.

Q: Which is more dangerous, hypoglycemia or hyperglycemia?

A: Both are dangerous. Hypoglycemia can cause life-threatening issues quickly (within minutes or hours), while hyperglycemia usually causes serious complications if sustained over longer periods. Severe, acute hyperglycemia (such as diabetic ketoacidosis) is also life-threatening.

Q: Can someone with diabetes prevent all blood sugar extremes?

A: Not always, but with diligent management—regular testing, appropriate medication, balanced diet, and healthy lifestyle—the frequency and severity of extremes can usually be minimized.

Q: What should you do if you’re not sure whether your symptoms are due to high or low blood sugar?

A: Test your blood sugar immediately if possible; treat according to the reading and symptoms. If in doubt and unable to test, treat for low blood sugar, as it is the more immediate danger, and seek medical advice.

Q: Do hyperglycemia and hypoglycemia affect people without diabetes?

A: Hypoglycemia without diabetes is rare and usually linked to other health conditions or medications. Persistent hyperglycemia in non-diabetics may be an early sign of diabetes or another medical problem and should be evaluated by a doctor.

References

Author

Sneha TeteBeauty & Lifestyle Writer

Sneha is a relationships and lifestyle writer with a strong foundation in applied linguistics and certified training in relationship coaching. She brings over five years of writing experience to thebridalbox, crafting thoughtful, research-driven content that empowers readers to build healthier relationships, boost emotional well-being, and embrace holistic living.

Read full bio of Sneha Tete