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Detecting the Signs: Hyperglycemia vs. Hypoglycemia

What does it mean to experience hyperglycemia and hypoglycemia? How can you recognize the symptoms of both, intervene early, and prevent serious episodes of high and low blood sugar?

If you were recently diagnosed with diabetes, you undoubtedly have heard the terms hyperglycemia and hypoglycemia from your healthcare team. And if you’ve had diabetes for some time now, it’s always good to get a refresher on the basics! There is no doubt that one of the main goals of diabetes management is to avoid both hypoglycemia and hyperglycemia. Hyperglycemia (high blood sugar) is the hallmark of diabetes onset, and it usually continues to occur on and off after you start treatment. On the other hand, hypoglycemia (low blood sugar) occurs as the result of diabetes treatment, particularly insulin administration. 

The two conditions fall on opposite ends of the glucose spectrum; your blood glucose is constantly rising and falling as a result of diabetes, its many therapies, and your lifestyle. Since both hyperglycemia and hypoglycemia pose significant long-term and short-term challenges, it’s important to understand what causes them, how to recognize the symptoms of each, and how to prevent and treat them. 

What is Hyperglycemia?

Hyperglycemia (or high blood sugar) and its accompanying symptoms are often what lead to a diabetes diagnosis (fasting glucose greater than 126 mg/dL, blood glucose level above 200 mg/dL, or an A1C above 6.4%).

Once you are diagnosed with diabetes and have started a treatment plan, the goal for most people is to spend as much time as possible in range with glucose levels between 70 and 180 mg/dL; when you start to approach or go above 180 mg/dL, that is considered hyperglycemia. If you are pregnant, the target is lower and you should aim to keep your glucose below 140 mg/dL as much as possible.

Hyperglycemia can occur for a number of reasons: 

  • Insufficient insulin, due to missed doses, or too low a dose for what is needed at the time, or not enough of your other diabetes medications 
  • Not enough physical activity (physical activity encourages the body to use glucose and makes the body more sensitive to insulin)
  • Too much food, particularly food containing high levels of carbohydrates (especially those with fast carbs)
  • Illness
  • Stress
  • Other medications and other medical conditions

Although most people with diabetes cannot avoid some high glucose levels, it is important to try to keep them at a minimum for two main reasons. First, prolonged, or persistent, hyperglycemia can lead to major health complications caused by damage to blood vessels and nerves, which can affect your eyes, heart, kidneys, and other organs. Second, mainly in type 1 diabetes (but also in some people with type 2 diabetes), significant and persistent hyperglycemia indicates you missed one or more doses of insulin or that the doses of insulin you took were insufficient to meet the needs of your body; if this persists, it can lead to diabetic ketoacidosis (DKA, or high levels of ketones in your blood). For more information on DKA, read “Ketosis vs. Ketoacidosis: what’s the Difference.”

What is Hypoglycemia?

Hypoglycemia (or low blood sugar) occurs when your glucose value drops below 70 mg/dL; serious hypoglycemia occurs below 54 mg/dL. Hypoglycemia is usually caused by too much insulin or insulin effect in the body. Here are some reasons why hypoglycemia might occur:

  • Too much insulin administered for your body’s needs at the time
  • Too high levels of other diabetes medications
  • Not enough food, particularly carbohydrates
  • Too much exercise
  • Illness, particularly if associated with vomiting, nausea, and diarrhea
  • Other medical conditions

Hypoglycemia can be quite dangerous, and in extreme cases it can cause you to become confused or even to lose consciousness (when there is not enough glucose for the brain to adequately function). Most people with diabetes are able to recognize the signs and symptoms of hypoglycemia as their glucose levels are trending low before severe hypoglycemia occurs. These warning signs are due to the release of other body hormones (mainly the hormone adrenaline) that alerts you to oncoming hypoglycemia. 

Some people experience hypoglycemia unawareness (which can also be called reduced hypoglycemia awareness) – this means the body doesn’t release the hormones or respond to the warning signals of hypoglycemia, putting them at a heightened risk of prolonged low glucose levels and glucose levels below which the brain can properly function. Several factors can increase the risk of being unaware of hypoglycemic episodes including having repeated episodes of hypoglycemia, going low while sleeping, exercise, consuming alcohol, having specific diabetes complications (like neuropathy), or taking certain prescription drugs. Because hypoglycemia unawareness more often occurs in those who were diagnosed with diabetes decades before, in addition to the risk factors mentioned, is more commonly occurs in people over the age of 65.

There are three levels of hypoglycemia: level 1, glucose values less than 70 mg/dL; level 2, glucose levels less than 54 mg/dL; and level 3, severe hypoglycemia, which is characterized by altered mental state or the need for someone to help you to treat the extreme low. 

Time in Range Goals – Stay Out of the Highs and the Lows

Effective diabetes management is an attempt to stay in the target glucose range. This means that you should aim to spend as much time as possible with your glucose level between 70 to 180 mg/dL The amount of time you spend in this target zone is called your Time in Range (TIR) and is measured by a continuous glucose monitor (CGM), though you can also measure TIR using your blood glucose meter. When glucose level exceeds 180 mg/dL, this is referred to as Time Above Range (TAR). If your glucose level goes below 70 mg/dL, this is Time Below Range (TBR). 

For most people with diabetes, these are the recommended TIR goals (If you have gestational diabetes, are pregnant and you have type 1 diabetes, or are elderly or high-risk, your TIR goals may differ):

  • At least 70% of the day in range (70-180 mg/dL or 3.9-10.0 mmol/L) – this is almost 17 hours a day
  • Less than 4% of the day below range (less than 70 mg/dL or 3.9 mmol/L) – this is 1 hour a day
    • Less than 1% of the Time Below Range less than 54 mg/dL or 3.0 mmol/L – this is 15 minutes a day
  • Minimize the time each day above range (greater than 180 mg/dL or 10.0 mmol/L) to less than 25% - this is 6 hours a day 
    • Less than 5% of the Time Above Range above 250 mg/dL or 13.9 mmol/L – this is 1 hour 15 minutes

These are general recommendations, however, you should strive for even more TIR and less Time Above and Below Range if possible. 

What are the Symptoms?

While it can sometimes be easy to recognize signs and tell the difference between hyperglycemia and hypoglycemia, at other times it can be hard to tell them apart because of some overlap. For example, confusion and headaches can occur in both cases. Try to be aware of any symptoms you experience that can help you differentiate between the two conditions. And talk to your care team to see if getting a CGM is something that could benefit you. CGM is a great tool to help you know when you are too high or too low.

Though not everyone experiences all of these symptoms every time, and it may take time to learn to recognize these symptoms quickly, here is what can occur with hyperglycemia and hypoglycemia:


(due to lack of insulin or insulin resistance)


(due to the release of other body hormones)

Severe Cases of Hypoglycemia 

(due to too little glucose in the brain)



Frequent and excessive urination 

Extreme thirst 

Dry mouth 

Blurry vision 


Shortness of breath






Trouble concentrating





Fast heartbeat





Loss of consciousness




How Do You Treat Hyperglycemia and Hypoglycemia?

The purpose of diabetes management is to regulate high and low glucose levels when they occur. Here are some strategies you might use to treat these conditions – it’s best to discuss these with your healthcare team before trying them. 


If you are on insulin, you may need to take a correction dose if your glucose level is too high, after discussing with your health care team.


Be sure you didn’t skip any diabetes medications. 


Drink more water.


Exercise – for example, you can go on a walk to bring your glucose levels down. Be sure to check your glucose level prior to exercising. If you are above 240 mg/dL, check your urine for ketones. If ketones are present, DO NOT exercise as this can make your glucose levels rise even higher.


Make sure that you stick to your medication regimen. Talk to your healthcare professional if this regimen is not keeping your glucose in range.

Have an emergency hypoglycemia kit that is easily accessible and with you at all times. Make sure people you are with know what to do in a hypoglycemic emergency.


Use the 15-15 rule. Eat or drink 15 grams of carbohydrates (glucose tablets, 4 oz of juice, 1 tablespoon of sugar or honey, small hard candies, etc.) to raise your blood sugar. Check it after 15 minutes. If it’s still below 70 mg/dL, have another serving of 15 grams of carbs. Repeat these steps until your blood sugar is at least 70 mg/dL. Once your blood sugar is back in range, you might consider eating a snack with little or no insulin to make sure it doesn’t drop again. If you use a closed loop device, discuss with your health care team if you should take less than 15 grams to correct a low glucose value. 


In severe cases, when a person is vomiting or not able to cooperate, coordinate swallowing, or fully conscious, glucagon should be used to treat hypoglycemia. Glucagon is a natural hormone that tells the body to release stored sugar into the bloodstream. Emergency glucagon is available by prescription and can be injected or inhaled.

How to Recognize an Emergency Situation?

Hyperglycemia can become an emergency if you begin to develop symptoms of DKA: shortness of breath, fruity-smelling breath, nausea and vomiting, confusion, or you lose consciousness. Likewise, hypoglycemia requires emergency care if you begin to experience confusion, a loss of consciousness, or seizures. Emergency glucagon can be an important addition to your emergency hypoglycemia kit. Learn more about emergency glucagon here.

If you start experiencing symptoms of DKA or severe hypoglycemia, or if a loved one notices signs of these symptoms, seek medical care immediately. 

Talk to your healthcare team if you are experiencing frequent episodes of hyperglycemia and/or hypoglycemia, if your glucose is consistently above 240 mg/dL, or anytime you experience severe hypoglycemia.

How to Prevent Going Too Low or Too High?

The best way to prevent glucose levels that are too high or too low is to practice careful diabetes management, checking your glucose often (either through self-monitoring of blood glucose, or if you are able to, with a CGM), and learning how to recognize the symptoms of both.

Try to get in the habit of checking your glucose:

  • Any time you have symptoms of hyperglycemia or hypoglycemia
  • Before and after meals
  • Before and after exercise
  • During exercise if it’s a long session
  • Before bed
  • In the middle of the night if you did intense exercise during the day
  • When you are sick
  • More frequently when aspects of your diabetes management routine change, such as new insulin or medication regimens, a new work schedule, an increase in physical activity, or traveling (especially across time zones)

It’s important to look at episodes of hyperglycemia and hypoglycemia as data points that can help you learn to prevent or reduce their frequency and severity. This data can also help you and your care team identify when a change to your diabetes care plan is needed such as a new medication or a refined approach to nutrition, exercise, or other lifestyle factors. By learning how to recognize the signs of both and by checking your glucose as often as is possible for you, you can catch hyperglycemia and hypoglycemia before they become severe.