Hypoglycemia refers to low levels of sugar, or glucose, in the blood. Hypoglycemia is not a disease, but it can indicate a health problem.

All the body’s cells, including the brain, need energy to function. Glucose supplies energy to the body. Insulin, a hormone, enables the cells to absorb and use it.

Signs of low blood sugar include hunger, trembling, heart racing, nausea, and sweating. In severe cases, it can lead to coma and death.

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

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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), note that symptoms usually appear when blood sugar levels are below 70 milligrams per deciliter (mg/dL).

However, this number can vary between individuals.

Blood glucose monitors are available for purchase online.

People with mild hypoglycemia may experience the following early symptoms:

  • hunger
  • tremor or trembling
  • sweating
  • shaking
  • a pale face
  • heart palpitations
  • rapid or irregular heart rate
  • dizziness and weakness
  • blurred vision
  • confusion

Severe hypoglycemia may involve:

  • weakness and tiredness
  • poor concentration
  • irritability and nervousness
  • confusion
  • irrational or argumentative behavior and personality changes
  • tingling in the mouth
  • coordination problems


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.

A person who regularly experiences hypoglycemia may become unaware that it is happening or getting worse. They will not notice the warning signs, and this can lead to severe and possibly fatal complications.

Hypoglycemia is often a sign of poorly managed diabetes.

Hypoglycemia can occur for various reasons.

Blood sugar regulation

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

Glucose enters the bloodstream after we eat. However, glucose needs insulin — a hormone that the pancreas produces — before it can enter a cell. In other words, even if there is plenty of glucose available, a cell will starve of energy if there is no insulin.

After eating, the pancreas automatically releases the right amount of insulin to move the glucose in blood into the cells. As glucose enters the cells, the 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.

Hypoglycemia and diabetes

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Testing blood sugar regularly can help those with diabetes to prevent hypoglycemia.

Both type 1 and type 2 diabetes involve a problem with insulin.

Type 1 diabetes: Damage to the cells that normally produce insulin means that the body cannot produce insulin.

Type 2 diabetes: The 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.

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

If the 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, both insulin and two other drugs can result in hypoglycemia. These drugs are sulfonylureas and meglitinides.

Hypoglycemia in children: Pediatric ketotic hypoglycemia

Some children experience pediatric ketotic hypoglycemia, involving low blood sugar levels and high levels of a substance known as ketones.

Doctors do not know exactly why this happens, but causes may include:

  • metabolism problems that the child was born
  • conditions that lead to excess production of certain hormones

Symptoms usually appear after the age of 6 months and disappear before adolescence.

They include:

  • fatigue
  • headaches
  • pale skin
  • confusion
  • dizziness
  • irritability
  • mood changes
  • clumsy or jerky movements

If a child shows any of the above signs or symptoms, they should see a doctor 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). They often go away after a few months, but sometimes they come back again.

Treatment can usually control the symptoms.

Symptoms and treatment are similar to those for hypoglycemia due to other causes.

Other causes

People may experience hypoglycemia for other reasons.

Some medications: Quinine, a drug that prevents malaria, can trigger hypoglycemia. High doses of salicylates, used to treat rheumatic disease, or propranolol for hypertension (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.

Not eating enough: People with eating disorders, such as anorexia nervosa, may experience dramatic falls in their blood sugar levels. Fasting or missing a meal may lead to low blood sugar levels.

Insulinoma: A tumor in the pancreas can cause the pancreas to produce too much insulin.

Increased activity: Increasing levels of physical activity can lower blood sugar levels for some time.

Endocrine problems: Some disorders of the adrenal and pituitary glands 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 different organs, including the pancreas. This can lead to hypoglycemia.

Anybody who experiences the symptoms of hypoglycemia but does not know why should see a doctor.

The doctor will probably:

  • 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 patient’s medical history and any medications they are taking
  • ask the person about their 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.
  • When glucose rises to normal levels, symptoms go away.

At the time of a visit to the doctor, 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 eating.

Learn more here about pancreatic cancer.

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woman drinking orange juice to treat hypoglycemia

A person who notices the signs of hypoglycemia should immediately consume:

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

These can bring rapid results. After this, they should eat slower-release carbohydrates, such as cereals, bread, rice, or fruit.

Glucose tablets are available to purchase online.

The next step is to seek treatment for any underlying cause,

For diabetes

A person with diabetes should check their blood glucose and treat the hypoglycemia, then wait 15–20 minutes and check their blood sugar again.

If blood glucose levels are still low, the person should repeat the process. They should eat some glucose, wait about 15–20 minutes, then check their blood sugar again.

People with diabetes need to keep to regular eating times. This will help to keep blood glucose levels stable

Severe symptoms

If symptoms are severe, and the individual cannot treat themselves, somebody else will need to apply honey, treacle, jam, or Glucogel to the inside of the cheeks and then gently massage the outside of the cheeks.

The person should start feeling better within 10–20 minutes.

Losing consciousness

If the person loses consciousness, someone should place them in the recovery position, and a qualified health professional should administer a glucagon injection.

If this is not possible, someone should call for emergency services to take the person to the emergency department of a hospital.

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

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Complex carbohydrates, such as brown rice, can help prevent hypoglycemia.

A number of dietary factors may help control hypoglycemia.

Low-sugar diet: A low intake of simple sugars and a high intake of complex carbohydrates is helpful. Complex carbs take longer to absorb, and this can help prevent glucose swings.

Small, frequent meals: Eating small meals at least three times a day can help maintain blood sugar levels.

Find out more about counting carbs in our dedicated article here.

Some people have recommended a low-sugar, high-protein diet for people with hypoglycemia, but this may reduce glucose tolerance and add unwanted fat to the diet.

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

Hypoglycemia: There is too little glucose in the blood, below 70 mg/dL.

Hyperglycemia: Glucose levels are too high, above 126 mg/L when fasting or 200 mg/dL 2 hours after eating.

Eating regular meals that include complex carbohydrates can prevent hypoglycemia for most people.

Those with a risk of hypoglycemia due to a medical condition should also:

Follow a treatment plan: It is important to follow the doctor’s instructions and seek help if symptoms change.

Checking blood glucose levels: Those at risk should check their blood sugar levels regularly and know how to recognize the symptoms.

Alcohol: Follow the daily alcohol limits that a doctor recommends and avoid drinking alcohol without food.

Exercise: Eat a carbohydrate-rich snack before exercising and be aware of how exercise can impact blood sugar levels.

Taking care when sick: Vomiting, for example, can prevent the body from absorbing enough energy.

Being ready: Carry a container of sugary fruit juice or a candy bar in case symptoms appear.

Letting people know: Those who are prone to low blood sugar should let friends, colleagues, and family members know.

Medical ID: Carrying 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 a number of medical conditions, including diabetes, may have a higher risk of hypoglycemia.

It is important to know how to recognize the symptoms and to be ready to take action if they occur.