Glucagon: function, benefits, foods and side effects

Glucagon is an important hormone that helps keep your blood sugar levels within a healthy range. While insulin lowers blood glucose when it rises after a meal, glucagon works in the opposite direction by helping increase blood glucose when it starts to fall. Together, these hormones play a central role in maintaining the body’s energy supply.

Although glucagon often receives less attention than insulin, it is essential for normal metabolism, particularly during fasting, between meals and during physical activity. It also has an important medical use: glucagon medication can help treat severe hypoglycemia, a potentially dangerous condition in which blood sugar drops too low.

Understanding how glucagon works can help you learn more about diabetes, blood sugar regulation, nutrition and metabolic health.

What is glucagon?

Glucagon is a peptide hormone produced by the alpha cells of the pancreas, an organ located behind the stomach. Its primary function is to prevent blood glucose levels from falling too low by signalling the liver to release stored glucose and produce additional glucose when needed.

When you eat carbohydrates, your digestive system breaks them down into glucose, which enters the bloodstream. Your body uses this glucose for energy, while some is stored in the liver and muscles as glycogen.

Between meals, during overnight fasting or when you exercise, glucose from food is no longer continuously entering your bloodstream. Glucagon helps maintain an adequate supply of glucose during these periods.

The hormone is also available as a medication. Manufactured glucagon is used in emergencies to treat severe hypoglycemia, particularly in people with diabetes who use insulin or certain glucose-lowering medicines.

It is important to distinguish between the glucagon your body naturally produces and glucagon medication. Natural glucagon helps regulate metabolism every day, whereas the medication is administered for specific medical purposes.

What is the function of glucagon?

The main function of glucagon is to increase blood glucose when the body needs more readily available energy. It achieves this primarily by acting on the liver.

1. Stimulates the breakdown of stored glucose

The liver stores glucose in the form of glycogen. When blood glucose levels fall, glucagon signals the liver to break down this stored glycogen into glucose.

This process is called glycogenolysis. The glucose is then released into the bloodstream, helping prevent blood sugar levels from dropping excessively.

This mechanism is particularly important between meals and during short periods of fasting.

2. Encourages the production of new glucose

The body cannot rely on stored glycogen indefinitely. During prolonged fasting, liver glycogen reserves become depleted.

Glucagon helps the liver produce glucose from non-carbohydrate sources, including certain amino acids and other metabolic compounds. This process is known as gluconeogenesis.

Gluconeogenesis helps maintain blood glucose when dietary carbohydrates are unavailable or insufficient.

3. Helps maintain energy availability

The brain and other tissues require a continuous energy supply. Although the body can use different fuels under certain conditions, glucose remains particularly important.

By helping maintain blood glucose, glucagon supports the body’s ability to supply energy between meals and during fasting.

4. Works alongside insulin

Glucagon and insulin work together to maintain blood sugar balance.

When blood glucose rises after a meal, insulin generally promotes glucose uptake and storage. When blood glucose falls, glucagon encourages the liver to release glucose.

The relationship is more complex than simply having two opposing hormones. Both respond to nutrient availability, and their secretion is influenced by several factors, including blood glucose, amino acids and other hormones.

5. Supports the body’s response to fasting

During fasting, the body must maintain an adequate supply of energy without receiving glucose from food.

Glucagon helps the liver release stored glucose and produce more glucose as needed. It also influences the way the body processes other nutrients during periods of reduced food intake.

This is one reason glucagon is an important hormone in normal metabolism.

How does glucagon work in the body?

Glucagon works through a signalling pathway that primarily targets liver cells.

When blood glucose falls, pancreatic alpha cells increase glucagon secretion. Glucagon travels through the bloodstream and binds to specific receptors on liver cells. This activates intracellular signalling pathways that stimulate glucose production and release.

The process can be summarised in four steps:

1. Blood glucose levels begin to fall.
2. The pancreas releases glucagon.
3. Glucagon signals the liver to break down glycogen and produce glucose.
4. Glucose enters the bloodstream, helping blood sugar return towards its normal range.

The amount of glucagon released depends on several factors, including the current glucose level, food intake, exercise and other hormonal signals.

In people with diabetes, this regulatory system may not function normally. Inappropriate glucagon secretion can contribute to elevated blood glucose, while an inadequate glucagon response can make hypoglycaemia more difficult to correct.

What is the difference between glucagon and insulin?

Glucagon and insulin are both produced by the pancreas, but their effects on blood glucose differ.

These hormones are essential partners in blood sugar regulation. Neither hormone works in isolation, and maintaining healthy glucose levels depends on the coordination of several organs, hormones and metabolic processes.

When is glucagon released?

Glucagon secretion changes according to the body’s energy requirements.

When blood sugar falls: A decline in blood glucose is an important stimulus for glucagon release. The hormone helps the liver provide additional glucose.

Between meals: Glucagon helps maintain blood glucose when you are not actively absorbing nutrients from food.

During fasting: As the time since your last meal increases, glucagon supports the liver’s production and release of glucose.

During exercise: Hormonal changes help ensure that adequate fuel remains available to working muscles and other tissues. The glucagon response varies according to exercise intensity, duration and nutritional status.

After eating protein-rich foods: Certain amino acids released during protein digestion can stimulate glucagon secretion. This response helps the body process dietary protein while maintaining glucose balance.

Glucagon secretion is carefully regulated. Its release does not depend on a single factor, and a rise in glucagon does not necessarily mean that blood glucose will become abnormally high.

What foods increase glucagon?

Certain foods, particularly those rich in protein, can stimulate the pancreas to release glucagon. This happens because amino acids produced during protein digestion act as signals to pancreatic alpha cells.

However, eating a particular food does not guarantee a predictable rise in glucagon. The response depends on the type and amount of food consumed, the accompanying nutrients and the body’s metabolic state.

1. Eggs

Eggs are a source of high-quality protein containing essential amino acids. Protein-rich foods such as eggs can stimulate glucagon secretion as part of the normal response to eating.

2. Dairy products

Milk, yoghurt and paneer provide protein and amino acids that contribute to normal nutrient metabolism.

The effect on glucagon depends on the product’s overall nutritional composition and what else is eaten alongside it.

3. Pulses and legumes

Lentils, chickpeas, kidney beans, peas and other legumes provide plant-based protein.

These foods can contribute amino acids that stimulate glucagon secretion. They also provide fibre, vitamins and minerals, making them useful components of a balanced diet.

4. Soy products

Soybeans, tofu and other soy-based foods provide plant protein. Like other protein-rich foods, they can influence glucagon release through the amino acids produced during digestion.

5. Nuts and seeds

Almonds, peanuts, walnuts, pumpkin seeds and other nuts and seeds contain varying amounts of protein and fat.

These nutrients influence several metabolic signals, including those involved in glucagon secretion. However, the hormonal response depends on the quantity consumed and the overall composition of the meal.

6. Fish, poultry and lean meat

For people who eat animal products, fish, chicken and lean meat provide protein and amino acids that can stimulate glucagon release.

Vegetarian protein sources can also contribute to this response. Animal protein is not essential for glucagon secretion.

Does eating protein always raise glucagon?

Not necessarily in the same way every time. Protein can stimulate both glucagon and insulin secretion. The balance between these hormones helps the body manage amino acids, glucose and other nutrients after a meal.

Glucagon secretion is also influenced by blood glucose, so the same protein-rich meal may produce different hormonal responses depending on the circumstances.

An important distinction: You do not generally need to eat foods specifically to increase glucagon. The aim of a healthy diet is to support balanced nutrition and normal blood glucose regulation, not to maximise the level of a single hormone.

If you have diabetes, follow a meal plan appropriate to your treatment and individual needs rather than trying to manipulate glucagon levels through diet.

What is glucagon medication used for?

Glucagon medication is primarily used to treat severe hypoglycemia, a condition in which blood glucose falls to a dangerously low level.

Severe hypoglycemia can affect the brain and nervous system. A person may become confused, lose consciousness or experience seizures, making it impossible for them to treat the episode safely by themselves.

Glucagon medication helps by signalling the liver to release stored glucose into the bloodstream.

Depending on the formulation available, glucagon may be administered as an injection under the skin, an injection into a muscle or a nasal powder. Certain formulations and routes are intended for administration by healthcare professionals.

The appropriate product and dose depend on the patient’s age, the formulation and the prescribed instructions.

When do you give glucagon?

Glucagon is generally given when a person experiences severe hypoglycaemia and cannot safely take glucose by mouth.

Situations in which emergency glucagon may be needed include:

• The person is unconscious or cannot be awakened normally.
• The person has a seizure associated with suspected severe hypoglycemia.
• The person is too confused or impaired to swallow safely.
• The person cannot safely treat their low blood sugar with oral glucose.

Glucagon may be prescribed for people with diabetes who are at risk of severe hypoglycaemia, particularly those using insulin or certain other glucose-lowering medicines.

Family members, caregivers and colleagues may be taught how to recognise severe hypoglycaemia and administer the prescribed glucagon product.

What should you do during a severe hypoglycaemic episode?

Severe hypoglycaemia is a medical emergency.

1. Get emergency help. Call your local emergency service, particularly if the person is unconscious, having a seizure or not recovering promptly.
2. Administer glucagon if available and indicated. Follow the instructions for the specific prescribed product. Do not delay emergency assistance.
3. Protect the person from injury. If they are unconscious but breathing normally, place them on their side when safe to do so. Glucagon can cause vomiting, so this position helps reduce the risk of choking.
4. Never give food, drinks or oral glucose to someone who is unconscious or unable to swallow safely.
5. Monitor their condition. Follow emergency-service instructions and check blood glucose when it is safe and practical to do so.

Once the person is fully awake and can swallow safely, give fast-acting oral carbohydrate according to their diabetes treatment plan or emergency-care advice. A follow-up snack or meal may also be needed to help prevent another episode.

Glucagon may not work adequately if the liver’s glycogen stores are severely depleted, such as after prolonged fasting, starvation or significant malnutrition. Emergency medical care remains essential even if the person appears to improve.

Who should not take glucagon?

Glucagon medication is not suitable for everyone. Its use depends on the person’s medical history, the reason for treatment and the specific formulation.

A known serious allergy to glucagon or any ingredient in the product is an important contraindication.

Certain medical conditions also require particular caution.

Pheochromocytoma

Pheochromocytoma is a rare tumour that can release excessive amounts of hormones such as adrenaline and noradrenaline.

Glucagon may trigger a dangerous rise in blood pressure in people with this condition. It is generally contraindicated in patients with pheochromocytoma.

Insulinoma

An insulinoma is a tumour of the pancreas that produces insulin. Glucagon may stimulate insulin release from certain insulinomas, potentially causing a subsequent fall in blood glucose.

Its use in people with insulinoma requires specific medical consideration and is generally contraindicated under standard product guidance.

Glucagonoma

A glucagonoma is a rare tumour that produces excessive glucagon. Additional glucagon may worsen the hormonal disturbance and associated high blood glucose.

Healthcare professionals need to assess the risks before using glucagon in someone with a glucagon-secreting tumour.

Severe malnutrition or depleted glycogen stores

Glucagon relies partly on stored glycogen in the liver to raise blood glucose. Its effect may be limited when glycogen reserves are depleted.

This can occur with prolonged fasting, starvation or significant malnutrition. Alternative glucose treatment and urgent medical assessment may be necessary.

Other medical considerations

People with adrenal insufficiency, significant heart disease or other complex medical conditions should tell their healthcare professional about their history before receiving glucagon in a planned medical setting.

These conditions do not all represent absolute contraindications in every situation. The decision depends on the formulation, clinical circumstances and urgency of treatment.

In a life-threatening hypoglycemic emergency, a trained responder should follow the prescribed emergency plan and seek immediate medical assistance rather than delaying care to investigate the person’s full medical history.

What are the side effects of glucagon?

Glucagon medication is generally well tolerated when used appropriately, but side effects can occur.

Common side effects include:

• Nausea and vomiting.
• Temporary headache.
• Dizziness or weakness.
• Injection-site discomfort, depending on the formulation.
• Temporary increases in heart rate or blood pressure in certain circumstances.

Nausea and vomiting are among the most common adverse effects. Vomiting is particularly important to consider in someone who has just recovered from severe hypoglycaemia because they may still be drowsy or confused.

Rarely, glucagon can cause serious allergic reactions. Symptoms may include widespread rash, itching, swelling of the face or throat, difficulty breathing or collapse. These symptoms require emergency medical attention.

Other serious complications may occur in specific circumstances, such as severe hypertension in someone with pheochromocytoma or recurrent hypoglycemia in a person with insulinoma.

What is the most serious side effect of glucagon?

One of the most serious potential side effects of glucagon is a severe allergic reaction, also known as anaphylaxis. Although rare, anaphylaxis can cause breathing difficulties, swelling, a sudden drop in blood pressure and potentially life-threatening complications.

Severe hypertension is another important risk in people with pheochromocytoma, which is why glucagon is generally contraindicated in this condition.

Nausea and vomiting are much more common than these serious reactions. However, any suspected severe allergic reaction after glucagon administration requires immediate emergency care.

It is also important to remember that severe hypoglycaemia itself can be life-threatening. When glucagon is indicated in an emergency, its potential benefits must be considered alongside its risks.

What happens when glucagon levels are abnormal?

Glucagon levels are influenced by several factors, and an abnormal result does not automatically indicate a specific disease.

High glucagon levels

Elevated glucagon can occur in several situations, including fasting, certain metabolic conditions and some forms of diabetes.

In diabetes, inappropriate glucagon secretion can contribute to excessive glucose production by the liver, making blood sugar harder to control.

Rarely, a glucagon-secreting pancreatic tumour called a glucagonoma can cause persistently elevated glucagon levels. Symptoms may include high blood glucose, unintended weight loss and a distinctive inflammatory skin rash.

Low glucagon levels

Low glucagon levels or an inadequate glucagon response may reduce the body’s ability to correct falling blood glucose.

This can be particularly relevant in people with diabetes who experience repeated episodes of hypoglycaemia.

However, glucagon levels are not routinely measured in everyone with diabetes. Testing is generally considered when there is a specific clinical reason to investigate abnormal hormone production or a suspected pancreatic condition.

How are glucagon levels tested?

A glucagon blood test measures the concentration of glucagon in a blood sample. A healthcare professional may request it when investigating a suspected glucagon-producing tumour or another condition affecting glucagon regulation.

The test involves collecting blood from a vein and sending the sample to a laboratory for analysis.

Glucagon testing can be technically demanding because sample handling and laboratory methods can influence the result. Interpretation also depends on factors such as fasting status, blood glucose levels and the laboratory’s reference range.

A result should therefore be interpreted alongside symptoms, medical history and other relevant investigations. A single glucagon measurement is not sufficient to diagnose every disorder of glucose metabolism.

For most people, blood glucose testing and other standard diabetes investigations are more relevant to routine monitoring than measuring glucagon directly.

How can you support healthy blood sugar regulation?

Glucagon is only one part of the body’s blood sugar control system. Maintaining healthy glucose levels involves several hormones, organs and lifestyle factors.

Consider the following measures:

Eat balanced meals. Include appropriate portions of carbohydrates, protein, healthy fats and fibre. The ideal balance depends on your nutritional requirements and any existing medical conditions.

Follow your diabetes treatment plan. If you use insulin or medicines that can cause hypoglycaemia, take them as prescribed and discuss recurrent low blood sugar with your healthcare professional.

Avoid skipping meals when your treatment makes this risky. People taking certain glucose-lowering medicines may need consistent meal timing or planned snacks. Individual advice is especially important for those at risk of hypoglycaemia.

Stay physically active. Regular physical activity supports metabolic health, but exercise can affect blood glucose. People using insulin or other medicines associated with hypoglycaemia should follow their individual exercise and glucose-monitoring plan.

Recognise warning signs. Shaking, sweating, dizziness, hunger, a rapid heartbeat and confusion can indicate low blood sugar. Severe confusion, seizures or unconsciousness require emergency action.

Seek medical advice when symptoms recur. Frequent episodes of low or high blood glucose may indicate that your treatment or another aspect of your health needs review.

These measures support overall metabolic health, but they do not replace prescribed treatment or emergency care.

Frequently asked questions about glucagon

1. What is glucagon and its function?

Glucagon is a hormone produced by the alpha cells of the pancreas. Its primary function is to raise blood glucose by stimulating the liver to break down stored glycogen and produce new glucose. It works alongside insulin to maintain blood sugar balance.

2. When do you give glucagon?

Glucagon medication is used for severe hypoglycaemia when a person cannot safely take glucose by mouth, such as when they are unconscious, having a seizure or too confused to swallow. Emergency medical assistance should be sought immediately, and the prescribed glucagon product should be used according to its instructions.

3. What foods increase glucagon?

Protein-rich foods such as eggs, dairy products, pulses, legumes, soy foods, nuts, seeds, fish and poultry can stimulate glucagon secretion because they provide amino acids. The response varies with the meal’s composition and the body’s metabolic state. You do not generally need to eat specific foods to increase glucagon.

4. Who should not take glucagon?

People with a known serious allergy to glucagon or its ingredients should not receive the relevant product. Glucagon is also generally contraindicated in people with pheochromocytoma or insulinoma. Certain other conditions, including glucagonoma and severe depletion of liver glycogen, require medical assessment because glucagon may be harmful or less effective.

5. What is the most serious side effect of glucagon?

A severe allergic reaction, including anaphylaxis, is a rare but potentially life-threatening side effect. Severe hypertension is another serious concern in people with pheochromocytoma. Nausea and vomiting are more common side effects.

6. Does glucagon increase or decrease blood sugar?

Glucagon increases blood glucose by signalling the liver to release stored glucose and produce additional glucose. Insulin generally lowers blood glucose by promoting glucose uptake and storage.

7. Is glucagon the same as glycogen?

No. Glucagon is a hormone, whereas glycogen is the stored form of glucose found mainly in the liver and muscles. Glucagon signals the liver to break down glycogen and release glucose into the bloodstream.

8. Can glucagon be used to treat diabetes?

Glucagon medication can be used to treat severe hypoglycaemia in people with diabetes. It does not replace insulin or routine diabetes treatment. It is an emergency medicine intended to raise dangerously low blood glucose when oral treatment is unsafe or impossible.

9. Can protein-rich foods increase glucagon without raising blood sugar?

Protein can stimulate glucagon release without producing the same immediate glucose response as a carbohydrate-rich meal. However, protein may also stimulate insulin secretion, and the overall blood glucose response depends on several factors. It is not possible to predict the response from protein intake alone.

10. Is a glucagon blood test necessary for everyone with diabetes?

No. Glucagon testing is not routinely required for everyone with diabetes. It may be ordered when a healthcare professional suspects a specific hormonal or pancreatic condition. Blood glucose measurements and other standard investigations are generally more useful for routine diabetes management.

Conclusion

Glucagon is an essential hormone that helps maintain blood glucose levels, particularly between meals, during fasting and when blood sugar begins to fall. By signalling the liver to release stored glucose and produce more glucose, it works alongside insulin to keep the body’s energy supply balanced.

Glucagon also has an important role in emergency medicine. When severe hypoglycaemia prevents someone from safely taking sugar by mouth, prescribed glucagon medication can help raise blood glucose while emergency care is arranged.

Understanding glucagon, the foods that can stimulate its release and the precautions associated with glucagon medication can help you make better-informed decisions about metabolic health. If you experience repeated episodes of low blood sugar, unexplained changes in glucose levels or symptoms that concern you, consult a qualified healthcare professional for appropriate assessment and treatment.

If you or a loved one experience symptoms of abnormal blood sugar levels, consult a healthcare provider or visit Sparsh Diagnostic Centre for accurate testing and timely management.

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Disclaimer:

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

 

Sources and further reading

The following medical institutions and scientific publications provide additional information about glucagon physiology, its clinical uses, potential adverse effects and blood testing.

1. Cleveland Clinic – Glucagon: What it is, function and related conditions. An overview of the hormone, its role in blood sugar regulation, fasting and related conditions.
   https://my.clevelandclinic.org/health/articles/22283-glucagon
2. NCBI Bookshelf – Glucagon, StatPearls. A clinical review covering glucagon’s mechanism of action, medical uses, contraindications and adverse effects.
   https://www.ncbi.nlm.nih.gov/books/NBK559195/
3. Kauvery Hospital – Role of glucagon. An educational overview of glucagon and its role in metabolism.
   https://www.kauveryhospital.com/nightingale/role-of-glucagon-v1i8/
4. Endocrinology and Metabolism – Scientific review on glucagon. A peer-reviewed resource discussing glucagon and its physiological and metabolic functions.
   https://www.e-enm.org/journal/view.php?number=2466
5. Beyond Type 1 – Glucagon. Educational information about glucagon and its use in managing severe hypoglycaemia in people with diabetes.
   https://beyondtype1.org/glucagon/
6. MedlinePlus – Glucagon blood test. Information about the purpose of glucagon testing and its clinical interpretation.
   https://medlineplus.gov/lab-tests/glucagon-blood-test/
7. American Journal of Physiology – Endocrinology and Metabolism. Scientific literature on glucagon and its role in metabolic regulation.
   https://journals.physiology.org/doi/10.1152/ajpendo.00492.2002

This article is an original educational synthesis informed by the above references. It should be reviewed by a qualified medical professional before publication as medically reviewed content.