Hypoglycemia refers to low levels of sugar, or glucose, in the blood. Low blood sugar can cause tiredness, shaking, and many other symptoms. It can be life threatening in severe cases. There are numerous possible causes of hypoglycemia.

All cells within the body, including in the brain, need energy to function. Glucose supplies energy, and the hormone insulin enables the cells to absorb and use it.

In severe cases, low blood sugar, or glucose, may lead to coma and death.

Hypoglycemia can occur with several conditions, but it most commonly happens as a reaction to diabetes medications, such as insulin. People with diabetes use insulin to treat high blood sugar.

This article explains hypoglycemia, including its symptoms and treatment options.

woman feeling faint with hypoglycemiaShare on Pinterest
Faintness can be an early sign of hypoglycemia.

Hypoglycemia happens when there is not enough glucose, or sugar, in the blood.

The National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) notes that symptoms usually appear when blood sugar levels are below 70 milligrams per deciliter (mg/dl). However, this number can vary between individuals. People can check with their doctor to find out their personal level of low blood sugar.

People with low blood sugar may want to use a blood glucose meter — a small, portable machine that monitors blood sugar levels. Some monitors sound an alarm if levels drop below a certain level. People can purchase blood glucose monitors online or discuss with their healthcare team.

Learn about home blood glucose monitors and how to use them here.

People with mild hypoglycemia may experience the following common symptoms:

Severe hypoglycemia may involve:

  • confusion
  • seizures
  • nightmares
  • fainting
  • coma


If a person does not take action, they may have:

  • difficulty eating or drinking
  • seizures
  • a loss of consciousness
  • coma

Severe hypoglycemia can be life threatening, and in rare cases, may lead to death without treatment.

Someone who regularly experiences hypoglycemia may be unaware that it is happening or getting worse. They may not notice the warning signs, which may lead to severe and possibly fatal complications.

People may experience hypoglycemia for reasons including:

  • Not eating enough: Fasting or missing a meal may lead to low blood sugar levels. Not eating enough carbohydrates can also cause blood sugar levels to fall.
  • Increased activity: Increasing physical activity levels can lower blood sugar levels for some time, especially in those with type 1 diabetes.
  • Some medications: Quinine, a drug that prevents malaria, can trigger hypoglycemia. High doses of salicylates, used to treat rheumatic disease, or propranolol for high blood pressure, may also cause blood sugar levels to drop. It can also happen when a person takes diabetes medication without having diabetes.
  • Alcohol consumption: Drinking large amounts of alcohol can cause the liver to stop releasing stored glucose into the bloodstream.
  • Some liver diseases: Drug-induced hepatitis can lead to hypoglycemia because it affects the liver.
  • Kidney disorders: People with a kidney disorder may have problems excreting medications. This can result in low blood sugar levels.
  • Insulinoma: A tumor in the pancreas can cause the pancreas to produce too much insulin.
  • Endocrine problems: Some adrenal and pituitary gland disorders can lead to hypoglycemia. This is more common in children than adults.
  • Reactive, or postprandial, hypoglycemia: The pancreas produces too much insulin after a meal.
  • Tumors: Rarely, a tumor in a part of the body other than the pancreas can cause hypoglycemia.
  • Severe illness: Some diseases, such as cancer, can affect many organs, including the pancreas. This can lead to hypoglycemia.

Blood sugar regulation

The digestive system breaks down carbohydrates from food. One of the molecules this creates is glucose, the body’s main energy source.

Glucose enters the bloodstream after we eat. Insulin, a hormone the pancreas produces, then allows cells in the body to absorb glucose. This means that even if plenty of glucose is available in the bloodstream, cells will starve of energy without insulin.

After eating, the pancreas automatically releases the right amount of insulin to allow cells to absorb enough glucose from the bloodstream. As glucose enters the cells, blood sugar levels fall.

Any extra glucose goes into the liver and muscles in the form of glycogen, or stored glucose. The body can use this glucose later when it needs more energy.

Insulin is responsible for bringing high blood sugar levels back to normal.

If glucose levels fall because an individual has not eaten for a while, the pancreas secretes glucagon, another hormone, which triggers the breakdown of stored glycogen into glucose.

The body then releases the glycogen into the bloodstream, bringing glucose levels back up.

If people take insulin and inject too much, it can cause cells to absorb excess glucose from the bloodstream, leading to low blood sugar.

Hypoglycemia and diabetes

Both type 1 and type 2 diabetes involve a problem with insulin. The American Diabetes Association (ADA) classes low blood sugar as less than 70 mg/dl.

Type 1 diabetesDamage to the cells that normally produce insulin means that the body cannot produce insulin.
Type 2 diabetesThe body’s cells do not respond properly to insulin, or the pancreas may not release enough insulin.

In both types of diabetes, the cells do not get enough energy from glucose.

People with type 1 diabetes and some with type 2 diabetes need to take insulin or other medications to reduce their blood sugar levels.

If the insulin dose is too high, blood sugar levels can fall too far, leading to hypoglycemia.

Hypoglycemia can also occur if the person exercises more than usual or does not eat enough.

A person does not need to increase their dose to have too much insulin in their body. It may be that the insulin they took was more than their body needed at that moment.

According to the NIDDK, insulin and two other diabetes medications — sulfonylureas and meglitinides — can result in hypoglycemia.

Learn about insulin resistance here.

Hypoglycemia in children: Pediatric ketotic hypoglycemia

Some children experience pediatric ketotic hypoglycemia, a condition involving low blood sugar levels and high levels of ketones. If people do not have enough glucose to use as energy, the body begins to break down fat in the body instead. The body produces chemicals called ketones as a by-product of breaking down fat.

According to a 2019 study, pediatric ketotic hypoglycemia usually occurs due to poor intake of food, a gastrointestinal illness and vomiting, or a period of prolonged fasting. Severe metabolic and hormonal conditions may also cause pediatric ketotic hypoglycemia.

Pediatric ketotic hypoglycemia may affect children from 6 months old and often resolves after the age of 6 years.


Symptoms of hypoglycemia in infants and children may include:

  • lethargy
  • abnormal crying
  • decreased feeding
  • jittery
  • irritability
  • confusion
  • drowsiness
  • sweating
  • pallor
  • pounding heart

If a child shows any of the above signs or symptoms, a doctor should examine them as soon as possible.

Insulin autoimmune syndrome

Another possible cause of hypoglycemia is insulin autoimmune syndrome, a rare disease that happens when the body’s immune system attacks insulin, mistaking it for an unwanted substance.

Symptoms tend to appear suddenly, according to the Genetic and Rare Diseases Information Center (GARD). Symptoms often go away after a few months, but they can return if blood sugar levels drop.

Symptoms and treatment are similar to those for hypoglycemia due to other causes. Treatment can usually control the symptoms.

Anybody with symptoms of hypoglycemia and does not know the underlying cause will need to consult with a doctor. A doctor may:

  • order a blood test to measure blood sugar levels
  • ask about symptoms and whether they improve after blood sugar levels return to normal
  • check the person’s medical history and any medications they are taking
  • ask about alcohol consumption

Whipple’s triad

A collection of three criteria, known as Whipple’s criteria, can suggest that symptoms stem from a pancreatic tumor.

The three criteria of Whipple’s triad are as follows:

  • signs and symptoms indicate hypoglycemia
  • when symptoms occur, a blood test shows low plasma glucose levels are less than 55 mg/dl
  • when glucose rises to normal levels, symptoms go away

During a doctor’s appointment, a person may not have symptoms. The doctor may ask them to fast for a time, usually overnight. This allows hypoglycemia to occur so that the doctor can make a diagnosis.

Some people may have to spend time in the hospital and fast for longer.

If symptoms appear after eating, they will need another glucose test after food.

Learn more here about pancreatic cancer.

A person who notices the signs of hypoglycemia should consume 15–20 grams (g) of carbohydrates or glucose, such as:

  • a glucose tablet
  • a sugar lump
  • a candy
  • a glass of fruit juice

They should then check blood sugar levels after 15 minutes, and eat another snack and repeat until their blood sugar levels are within a normal range. After this, people can eat slower-release carbohydrates, such as cereal, bread, rice, or fruit.

People will also need to seek treatment for any underlying cause.

For diabetes

A person with diabetes can follow the 15:15 rule.

They will need to check their blood sugar, treat the hypoglycemia with 15g of carbohydrate, and then wait 15 minutes and recheck their levels.

If their blood sugar levels are still low, the person should repeat the process. They should eat some glucose, wait about 15 minutes, then recheck their blood sugar.

People with diabetes may need to follow regular eating times to help keep blood sugar levels stable.

Severe symptoms

If symptoms are severe, and the individual cannot treat themselves, somebody else will need to give them glucagon through an injection or via the nose. People will usually regain consciousness within 5–15 minutes but may then experience nausea or vomiting.

Losing consciousness

If the person loses consciousness, someone will need to place them in the recovery position and administer a glucagon injection. If this is not possible, people will need to call 911 immediately.

It is important not to place food or drink into the mouth of an unconscious person, as it could block the airways.

Do not drive with low blood sugar

People will need to avoid driving while they have low blood sugar levels as it could be dangerous. People will need to wait until their levels return to within a normal range before driving.

If people start to experience symptoms of hypoglycemia while driving, they will need to safely stop the car and check their blood sugar levels.

People may find it helpful to store quick-acting carbohydrates, such as orange juice or glucose tablets, in their car if their levels drop while driving.

If people have hypoglycemia or diabetes, they can discuss an eating plan with a healthcare provider. Tips may include the following:

  • eating snacks and small meals around every three hours throughout the day
  • opting for a variety of foods, including protein, high-fat foods, and high-fiber foods
  • limiting foods high in sugar

Learn about counting carbs with diabetes here.

Hypoglycemia and hyperglycemia both relate to blood sugar levels, but they are not the same.

HypoglycemiaThere is too little glucose in the blood, below 70 mg/dl.
HyperglycemiaGlucose levels are too high, 125 mg/dl during fasting and more than 180 mg/dl two hours after eating.

Learn about hyperglycemia and diabetes here.

Preventing hypoglycemia will depend on the underlying cause. Managing the underlying condition can help to avoid hypoglycemia. There are steps people can consider that may help. These include:

  • Following a treatment plan: It is important to follow doctor’s instructions and seek help if symptoms change.
  • Checking blood glucose levels: People at risk should check their blood sugar levels regularly and know how to recognize the symptoms.
  • Following alcohol guidelines: Sticking to the daily alcohol limits that a doctor recommends and avoid drinking alcohol without food.
  • Being aware of exercise: Eating a carbohydrate-rich snack before exercising and understanding how physical activity can impact blood sugar levels.
  • Taking care when sick: Vomiting, for example, can prevent the body from absorbing enough energy.
  • Being prepared: Carrying a container of sugary fruit juice or a candy bar in case symptoms appear.
  • Telling people: Those prone to low blood sugar should inform friends, colleagues, and family members.
  • Carrying medical ID: A form of ID or medical bracelet will enable healthcare providers, emergency services, and others to know what to do sooner.

Hypoglycemia can lead to symptoms such as dizziness, weakness, and, in severe cases, a loss of consciousness.

People with some medical conditions, including diabetes, may have a higher risk of hypoglycemia.

It is important for people to know how to recognize the symptoms and be ready to take action if they occur. Consuming carbohydrates or glucose when blood sugar levels drop can help return them to a normal range.