Hyperglycemia vs Hypoglycemia: What’s the Difference?

If you live with diabetes, you know that controlling blood sugar within a narrow range can be difficult.

Especially if you have a hard time deciphering what hyperglycemia (high) and hypoglycemia (low) blood sugar looks like.

Even more confusing, the symptoms of both conditions can be very similar.

So how do you tell the difference between high and low blood sugar?

This article describes both hyperglycemia and hypoglycemia, their symptoms, and how to distinguish between them when it matters most.

What is hyperglycemia?

Hyperglycemia is also known as high blood sugar, which means that the blood glucose level is higher than normal. This can happen in both people with and without diabetes.

Normal blood sugar levels can vary, but a non-diabetic person’s blood sugar level after fasting (without eating for at least 2 hours) is usually 99 mg/dL or less.

100-125 mg/dL indicates pre-diabetes, and a value above 125 mg/dL on an empty stomach indicates diabetes.

In people without diabetes, episodes of hyperglycemia are short-lived.

However, people with diabetes typically need to exercise or take prescribed medications to lower their blood sugar levels.

People with diabetes can have very high blood sugar, and when this happens, it can turn into diabetic ketoacidosis (DKA), which can be life-threatening if left untreated.

What are the causes of hyperglycemia?

In people without diabetes, higher than normal blood sugar levels are usually caused by eating something sweet or taking medications such as steroids.

In people with diabetes, high blood sugar is a direct result of too little or no endogenous insulin (produced by the pancreas) in the blood.

Diabetes means that your blood sugar will always be high by default without the right medications to bring it down.

Acute episodes of hyperglycemia can be caused by:

  • Consuming too many grams of sugar or carbohydrates with too little insulin or medication
  • Not enough exercise
  • Being sick or suffering from an infection
  • Experiencing insulin resistance
  • Being stressed
  • Not enough sleep
  • Some medications
  • Dehydration

In fact, over 42 different variables can cause changes in blood sugar levels in people with diabetes.

What are the symptoms of hyperglycemia?

The symptoms of hyperglycemia are the same that many people experience after being diagnosed with diabetes, and include:

  • Extreme thirst
  • Dry mouth
  • Frequent urination
  • Fruity breath smell
  • Tiredness
  • Headache
  • Body pain
  • Blurred vision
  • In extreme cases, weight loss
  • In extreme and long-term cases, inability to recover from infection
  • In extreme cases, DKA

If you experience any of these symptoms and have diabetes, check for ketones immediately and seek medical attention.

If you experience any of these symptoms and have not been diagnosed with diabetes, contact your doctor immediately for a diabetes test.

What is hypoglycemia?

Hypoglycemia is also known as low blood sugar.

This happens when there is too little glucose in the blood for the body to function properly.

This can happen in both people with and without diabetes.

Low blood sugar can vary. However, anything below 70 mg/dL is considered low in both people with and without diabetes.

People who have low blood sugar will need any form of glucose (sugar) to bring their blood sugar levels back to normal.

For low blood sugar that is not severe, eating 15 to 20 grams of carbohydrate will bring someone back into the normal range, but it varies from person to person.

Check with your doctor if you are unsure how much carbohydrate you will need to treat typical low blood sugar.

Severe low blood sugar is more likely to occur if you are taking exogenous insulin (insulin that is injected or taken with an insulin pump).

Your liver typically throws glucose into your bloodstream to prevent a catastrophic decline.

If someone with diabetes experiences very low blood sugar and their liver does not, they will need injections of the hormone glucagon (available in a pre-filled pen or inhaler).

This will cause their liver to release glucose into the bloodstream and could save lives.

Unfortunately, as many as 25% of people with type 1 diabetes (and many with type 2 diabetes) are hypo-unconscious when they can’t detect low blood sugar.

What are the causes of hypoglycemia?

In people without diabetes, hypoglycemia can be the result of fasting, eating too little carbohydrate, strenuous exercise, or taking certain medications.

In people with diabetes, hypoglycemia is the result of:

  • Taking too much insulin or other diabetes medicines
  • Consuming too few carbohydrates
  • Drinking alcohol
  • Changes in your insulin or medication regimen
  • Unexpected changes to your schedule
  • Hot and humid weather

Even if you are able to detect low blood sugar, it is important to be able to recognize the symptoms of low blood sugar before they become serious.

What are the symptoms of hypoglycemia?

Symptoms of low blood sugar can vary, but typically include:

  • Trembling
  • Exploitation
  • Confusion
  • Tiredness
  • Fast heartbeat
  • Dizziness
  • Hunger
  • Bow
  • In extreme cases, diabetic coma
  • In extreme cases, death

How to tell the difference between high and low blood sugar?

In some cases, the symptoms of high and low blood sugar can mimic each other, especially if they occur at night when you’re not as alert and awake.

Feelings of confusion and fatigue occur when blood sugar levels are both high and low.

However, feeling lethargic and aching muscles are classic symptoms of high blood sugar.

Feeling jittery and nervous with a fast heartbeat and sweating are classic symptoms of low blood sugar.

If you’re having trouble deciphering between the two, wearing a continuous glucose monitor (CGM) may help, especially for nighttime blood sugar levels.

If you choose (or cannot) not wear a CGM, frequent blood sugar testing may confirm the symptoms you are experiencing.

Additionally, if you struggle with hypoglycemia unawareness, having a diabetes alert dog (DAD) that is trained to detect both high and low blood sugar levels can help detect and treat these episodes before they become medical emergencies.

Many people are unable to tell the difference between low, normal and high blood sugar if their diabetes treatment has become loose or they do not have very tight blood sugar control.

Watching your blood sugar more closely and treating higher blood sugar more aggressively will allow you to experience symptoms of hyperglycemia earlier.

The same advice applies to low blood sugar.

If you start treating hypoglycemic episodes when your blood sugar reaches 80 mg/dL instead of 70 mg/dL, you may start to feel your blood sugar approaching 80 mg/dL instead of having no symptoms until your blood sugar no, the level is at the much more dangerous level of 60 mg/dL.

Talk to your doctor if you’re concerned you may not be feeling your ups and downs, and see what recommendations they might have for you.


It is best to prevent both high and low blood sugar as much as possible. Watch your blood sugar carefully and treat both highs and lows before they become problematic.

Take all diabetes medications as directed and try to manage your sleep, exercise, diet and stress in a healthy way.

Keep a food diary, especially if you have problems with high or low blood sugar after meals, and take notes about how you feel after eating certain foods or doing certain activities.

Try to do what’s best for you and your diabetes management.

Be consistent about the timing of exercise and activities, meals, and medications.

Seek support from family and friends and talk to your doctor about what works (and what doesn’t) when it comes to managing your diabetes.

Remember, it’s your life, and if something doesn’t work, you can always (and encourage) change it!


People with and without diabetes can experience hyperglycemia (high) and hypoglycemia (low) blood sugar levels.

A high fasting blood sugar level in a person without diabetes is over 99 mg/dL, and a high fasting blood sugar level in a person with diabetes is over 125 mg/dL.

Low blood sugar in people with and without diabetes is below 70 mg/dL.

There are many different causes of high and low blood sugar, but for people with insulin-dependent diabetes, it’s usually a matter of taking too much insulin (low blood sugar) or too little insulin (high blood sugar).

Both levels can be dangerous to your health, so it’s important to notice the symptoms of each and act accordingly.

Symptoms of high blood sugar include thirst, frequent urination, muscle aches and fatigue.

While symptoms of low blood sugar include jitteriness, nervousness, sweating and fatigue.

Several symptoms of low and high blood sugar overlap, so it’s important to manually check your blood sugar frequently to confirm any symptoms you’re experiencing.

In addition, using a continuous glucose monitor (CGM) may be helpful. If you struggle with hypo unconsciousness, use a diabetes alert dog (DAD) that can sense high and low blood sugar levels.

Taking preventive measures to avoid dangerously high and low blood sugar levels is crucial.

Always take your medications as directed, carry snacks to treat low blood sugar, stick to a schedule, and try to create a healthy sleep, stress management, and exercise routine.

Talk to your doctor about any concerns you have about frequent low and high blood sugar levels and how to treat and prevent them.

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