Home Medical Topics Hypoglycemia (Low Blood Glucose) – Signs, Causes & Treatment

Hypoglycemia (Low Blood Glucose) – Signs, Causes & Treatment



Hypoglycemia, Blood glucose (also known as blood sugar) levels will change during the day based on a variety of circumstances, either going up or down. That is typical. You probably won’t be able to detect if it fluctuates only little within a certain range. However, it can become harmful if it falls below the healthy limit and is left untreated.

Low blood sugar occurs when your blood glucose levels have dropped so far below target that you must take measures to raise them. Typically, this occurs when your blood glucose level is under 70 mg/dL. However, discuss your personal blood glucose goals and what is too low for you with your diabetes care team.

Another name for low blood sugar is insulin response or insulin shock.

Signs and symptoms

Each person’s reaction to low blood glucose levels is unique. Learn your personal signs and symptoms of low blood glucose. Taking the time to jot down these symptoms may help you discover your personal signs of low blood glucose. Signs and symptoms of low blood glucose range from milder, more typical indications to the most severe:

  • Feeling shaky
  • Being nervous or anxious
  • Sweating, chills and clamminess
  • Irritability or impatience
  • Confusion
  • Fast heartbeat
  • Feeling lightheaded or dizzy
  • Hunger
  • Nausea
  • Color draining from the skin (pallor)
  • Feeling sleepy
  • Feeling weak or having no energy
  • Blurred/impaired vision
  • Tingling or numbness in the lips, tongue, or cheeks
  • Headaches
  • Coordination problems, clumsiness
  • Nightmares or crying out during sleep
  • Seizures

The only sure way to know whether you are experiencing low blood glucose is to check your blood glucose levels, if possible. If you are experiencing symptoms and you are unable to check your blood glucose for any reason, treat the hypoglycemia.

A low blood glucose level triggers the release of epinephrine (adrenaline), the “fight-or-flight” hormone. Epinephrine is what can cause the symptoms of hypoglycemia such as thumping heart, sweating, tingling, and anxiety.

If the blood sugar glucose continues to drop, the brain does not get enough glucose and stops functioning as it should. This can lead to blurred vision, difficulty concentrating, confused thinking, slurred speech, numbness, and drowsiness. If blood glucose stays low for too long, starving the brain of glucose, it may lead to seizures, coma, and very rarely death.


Low blood glucose is common for people with type 1 diabetes and can occur in people with type 2 diabetes taking insulin or certain medications. The average person with type 1 diabetes may experience up to two episodes of mild low blood glucose each week, and that’s only counting episodes with symptoms. If you add in lows without symptoms and the ones that happen overnight, the number would likely be higher.


The 15-15 rule —have 15 grams of carbohydrate to raise your blood glucose and check it after 15 minutes. If it’s still below 70 mg/dL, have another serving.

Repeat these steps until your blood glucose is at least 70 mg/dL. Once your blood glucose is back to normal, eat a meal or snack to make sure it doesn’t lower again.

This may be:

  • Glucose tablets (see instructions)
  • Gel tube (see instructions)
  • 4 ounces (1/2 cup) of juice or regular soda (not diet)
  • 1 tablespoon of sugar, honey, or corn syrup
  • Hard candies, jellybeans, or gumdrops—see food label for how many to consume

Make a note about any episodes of low blood glucose and talk with your health care team about why it happened. They can suggest ways to avoid low blood glucose in the future.

Many people tend to want to eat as much as they can until they feel better. This can cause blood glucose levels to shoot way up. Using the step-wise approach of the “15-15 Rule” can help you avoid this, preventing high blood glucose levels.


  • Young children usually need less than 15 grams of carbs to fix a low blood glucose level: Infants may need 6 grams, toddlers may need 8 grams, and small children may need 10 grams. This needs to be individualized for the patient, so discuss the amount needed with your diabetes team.
  • When treating a low, the choice of carbohydrate source is important. Complex carbohydrates, or foods that contain fats along with carbs (like chocolate) can slow the absorption of glucose and should not be used to treat an emergency low.
Severe hypoglycemia

When low blood glucose isn’t treated and you need someone to help you recover, it is considered a severe event.

Treating severe hypoglycemia

Glucagon is a hormone produced in the pancreas that stimulates your liver to release stored glucose into your bloodstream when your blood glucose levels are too low. Glucagon is used to treat someone with diabetes when their blood glucose is too low to treat using the 15-15 rule.

Glucagon is available by prescription and is either injected or administered or puffed into the nostril. For those who are familiar with injectable glucagon, there are now two injectable glucagon products on the market—one that comes in a kit and one that is pre-mixed and ready to use. Speak with your doctor about whether you should buy a glucagon product, and how and when to use it.

The people you are in frequent contact with (for example, friends, family members, and coworkers) should be instructed on how to give you glucagon to treat severe hypoglycemia. If you have needed glucagon, let your doctor know so you can discuss ways to prevent severe hypoglycemia in the future.


Too much insulin is a definite cause of low blood glucose. One reason newer insulins are preferred over NPH and regular insulin is that they’re less likely to cause blood glucose lows, particularly overnight. Insulin pumps may also reduce the risk for low blood glucose. 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 glucose.


What you eat can cause low blood glucose, including:

  • Not enough carbohydrates.
  • Eating foods with less carbohydrate than usual without reducing the amount of insulin taken.
  • Timing of insulin based on whether your carbs are from liquids versus solids can affect blood glucose levels. Liquids are absorbed much faster than solids, so timing the insulin dose to the absorption of glucose from foods can be tricky.
  • The composition of the meal—how much fat, protein, and fiber are present—can also affect the absorption of carbohydrates.

Hypoglycemia unawareness

Very often, hypoglycemia symptoms occur when blood glucose levels fall below 70 mg/dL. As unpleasant as they may be, the symptoms of low blood glucose are useful. These symptoms tell you that you your blood glucose is low and you need to take action to bring it back into a safe range. But, many people have blood glucose readings below this level and feel no symptoms. This is called hypoglycemia unawareness.

People with hypoglycemia unawareness can’t tell when their blood glucose gets low so they don’t know they need to treat it. Hypoglycemia unawareness puts the person at increased risk for severe low blood glucose reactions (when they need someone to help them recover). People with hypoglycemia unawareness are also less likely to be awakened from sleep when hypoglycemia occurs at night. People with hypoglycemia unawareness need to take extra care to check blood glucose frequently. This is especially important prior to and during critical tasks such as driving. A continuous glucose monitor (CGM) can sound an alarm when blood glucose levels are low or start to fall. This can be a big help for people with hypoglycemia unawareness.

Hypoglycemia unawareness occurs more frequently in those who:

  • Frequently have low blood glucose episodes (which can cause you to stop sensing the early warning signs of hypoglycemia).
  • Have had diabetes for a long time.
  • Tightly manage their diabetes (which increases your chances of having low blood glucose reactions).

If you think you have hypoglycemia unawareness, speak with your health care provider. Your health care provider may adjust/raise your blood glucose targets to avoid further hypoglycemia and risk of future episodes.

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