Insulin: what it is, how it works, normal levels, high insulin and more

Insulin is one of the most important hormones in the human body. It helps move glucose from the bloodstream into cells, where it can be used for energy. It also influences how the body stores and uses carbohydrates, fats and proteins.

Although insulin is most commonly discussed in relation to diabetes, its role is much broader. Problems can occur when the body produces too little insulin, produces more insulin than necessary, or when cells stop responding properly to the insulin being produced.

Understanding insulin can make blood sugar reports, diabetes tests and terms such as insulin resistance, hyperinsulinemia and hypoglycemia much easier to understand.

This guide explains what insulin does, where it comes from, what normal insulin levels mean, how insulin is tested, what happens when insulin is too high or too low, and which foods can stimulate insulin release.

What is insulin and what is its function?

Insulin is a hormone produced by the beta cells of the pancreas, specifically in structures called the islets of Langerhans.

Its best-known function is to help control blood glucose. After you eat, carbohydrates are broken down into glucose and absorbed into the bloodstream. As blood glucose rises, the pancreas releases insulin.

Insulin essentially helps glucose move from the blood into cells, particularly muscle and fat cells, where it can be used for energy. It also helps the liver store glucose for later use.

A simple way to think about insulin is as a signal that tells the body’s cells to use or store available glucose.

Insulin also affects fat metabolism. It generally promotes energy storage after meals and suppresses the breakdown of stored fat when insulin levels are elevated.

When insulin is insufficient or the body’s cells don’t respond adequately to it, glucose remains in the bloodstream and blood sugar can rise.

What organ produces insulin?

The pancreas produces insulin.

More specifically, insulin is made by beta cells located in the pancreatic islets. The pancreas has several other important functions, including producing digestive enzymes and other hormones involved in blood sugar regulation.

The pancreas continuously adjusts insulin production according to factors such as:

• Blood glucose levels
• Food intake
• The amount and type of carbohydrates consumed
• Physical activity
• Stress and illness
• Other hormones
• Certain medicines

This is why insulin levels naturally change throughout the day rather than remaining at one fixed number.

What happens when you lack insulin?

When the body does not have enough effective insulin, glucose cannot be adequately moved from the bloodstream into cells.

As a result, blood glucose rises.

The consequences depend on the cause and severity of the insulin deficiency.

In type 1 diabetes, the immune system destroys insulin-producing beta cells, eventually resulting in very little or no natural insulin production. People with type 1 diabetes therefore need insulin replacement to survive.

A severe lack of insulin can cause the body to start breaking down fat rapidly, producing acidic substances called ketones. This can result in diabetic ketoacidosis (DKA), a medical emergency.

Symptoms of DKA can include:

• Excessive thirst
• Frequent urination
• Nausea or vomiting
• Abdominal pain
• Deep or rapid breathing
• Fruity-smelling breath
• Severe weakness or confusion

A person with insulin-dependent diabetes should never stop prescribed insulin without medical advice.

What happens when insulin levels are high?

High insulin levels are known as hyperinsulinemia.

High insulin does not automatically mean that someone has diabetes. In fact, insulin can be high while blood glucose is still within the normal range, particularly during the early stages of insulin resistance.

One common reason for high insulin is insulin resistance. In this situation, muscle, liver and fat cells do not respond as effectively to insulin. The pancreas may compensate by producing more insulin to keep blood glucose under control.

Over time, however, the pancreas may struggle to compensate. Blood glucose can then begin to rise, potentially progressing from insulin resistance to prediabetes and eventually type 2 diabetes.

Other causes of unusually high insulin can include excessive insulin medication or, rarely, an insulin-producing tumour such as an insulinoma. High insulin accompanied by low blood glucose needs medical evaluation.

What is a normal insulin level?

There is no single universal insulin level that is considered normal for everyone.

Unlike blood glucose, insulin does not have one widely applicable target range that can be interpreted without considering the circumstances of the test. Insulin levels change depending on whether you have eaten, what you ate, your physical activity, stress, illness, medications and other factors.

Laboratories may provide their own reference ranges for fasting insulin tests. Therefore, your result should be interpreted using the reference interval printed on your laboratory report, along with your blood glucose and clinical history.

A fasting insulin result by itself usually does not diagnose diabetes.

What is the normal insulin level by age?

There is no universally accepted normal insulin range divided into specific age groups for routine clinical interpretation.

Children, teenagers and adults can have different insulin requirements, and insulin secretion changes with factors such as puberty, body composition, diet, activity and health conditions.

Therefore, it would be misleading to say that everyone aged 20, 40 or 60 should have one particular insulin number.

The laboratory’s reference range, whether you were fasting, your blood glucose level and the reason the test was ordered all matter when interpreting an insulin result.

How to check insulin level?

Insulin is usually checked with a blood test.

Depending on the clinical question, your healthcare professional may request:

• Fasting insulin
• Insulin alongside fasting glucose
• Glucose tolerance testing with insulin measurements
• C-peptide
• Other diabetes-related tests

A fasting insulin test generally requires fasting according to the laboratory’s instructions. Your doctor may recommend measuring glucose at the same time because insulin levels are much easier to interpret when considered alongside blood glucose.

C-peptide can also provide useful information because the pancreas releases insulin and C-peptide together. C-peptide remains in the bloodstream longer and can therefore help assess how much insulin the pancreas is producing.

If you have an insulin result that appears unusually high or low, don’t interpret the number in isolation.

What is a bad insulin score?

There isn’t a medically recognised single “bad insulin score.”

People sometimes use this phrase when discussing fasting insulin, insulin resistance scores or online calculators. However, insulin resistance cannot always be determined from one insulin number.

Doctors may consider several measurements together, including:

• Fasting glucose
• Fasting insulin
• HbA1c
• Oral glucose tolerance test results
• C-peptide
• Body weight and waist circumference
• Blood pressure and lipid profile
• Medical history

Some clinicians may calculate an insulin-resistance estimate such as HOMA-IR using fasting glucose and fasting insulin. However, there is no single HOMA-IR cutoff that applies universally to every population and laboratory.

If you have been given an insulin resistance score, it is best interpreted by a healthcare professional who knows the method and reference range used.

What is a type 2 diabetes sugar level?

There is no single blood sugar number that defines every aspect of type 2 diabetes. Diagnosis can be made using several accepted tests.

For non-pregnant adults, commonly used diagnostic thresholds include:

Diagnostic testing generally needs appropriate clinical confirmation rather than relying on a single home glucose reading.

These are blood glucose criteria, not insulin criteria. A person can have insulin resistance and high insulin before their blood glucose reaches the diabetes range.

What are the 3 main types of insulin?

If you mean insulin medicines, there are several categories based on how quickly they begin working and how long their effects last.

Three commonly discussed groups are:

Rapid-acting insulin

Rapid-acting insulin starts working relatively quickly and is commonly used around mealtimes.

Examples include insulin lispro, insulin aspart and insulin glulisine.

Short-acting insulin

Regular insulin is generally classified as short-acting insulin. It takes longer to begin working than rapid-acting insulin and can have a longer duration of action.

Long-acting insulin

Long-acting insulin provides a more sustained insulin effect and is generally used as background or basal insulin.

Examples include insulin glargine and insulin degludec.

There are also intermediate-acting and ultra-long-acting insulins, so describing insulin medicines as only three types is an oversimplification. Insulin is selected according to a person’s diabetes type, blood glucose pattern, meals, lifestyle and treatment plan. Cleveland Clinic

Which foods increase insulin?

Foods that contain carbohydrates generally stimulate insulin release because carbohydrates are broken down into glucose.

However, the insulin response isn’t determined simply by whether a food is labelled “good” or “bad.”

Foods that can produce a substantial insulin response include:

• Sugar and sweets
• Soft drinks and sweetened beverages
• White bread
• Refined breakfast cereals
• Cakes and biscuits
• White rice
• Potatoes
• Refined flour products
• Many processed snack foods

Protein-rich foods can also stimulate insulin secretion, even when they contain little carbohydrate. Mixed meals containing carbohydrates, protein and fat can therefore produce different insulin responses depending on the meal composition.

A useful dietary goal isn’t necessarily to eliminate every food that stimulates insulin. Insulin is a normal and necessary hormone, and eating naturally causes insulin to rise.

Instead, a balanced diet containing vegetables, whole grains, legumes, adequate protein, fruit in appropriate portions and minimally processed foods can support healthier blood glucose management.

What foods cause too much insulin?

There is no single food that automatically causes “too much insulin” in everyone.

Large amounts of rapidly absorbed carbohydrates, especially sugary drinks and highly refined foods, can cause a rapid rise in blood glucose and consequently stimulate insulin secretion.

Regularly consuming excess calories can also contribute to weight gain and insulin resistance in susceptible people. When cells become less responsive to insulin, the pancreas may compensate by producing more insulin.

Rather than focusing on eliminating one particular food, it is generally more useful to look at the overall dietary pattern, portion sizes, physical activity, body composition and metabolic health.

Is high insulin curable?

Whether high insulin can be reversed depends on why the insulin is high.

When high insulin is associated with insulin resistance, improving insulin sensitivity can reduce the amount of insulin the body needs to maintain blood glucose.

Lifestyle measures may include:

• Regular physical activity
• Maintaining a healthy body weight where appropriate
• Eating a balanced, minimally processed diet
• Getting adequate sleep
• Managing stress
• Avoiding tobacco
• Following prescribed treatment for diabetes or related conditions

Some people with insulin resistance can substantially improve their metabolic health with lifestyle changes and medical treatment.

However, high insulin caused by a specific medical condition, medication or an insulin-producing tumour requires treatment directed at that underlying cause.

So, rather than asking whether high insulin itself is “curable,” it is more useful to ask what is causing the high insulin and whether that cause can be treated or reversed.

Can you live without insulin?

A person cannot live indefinitely without insulin.

This is particularly important for people with type 1 diabetes, whose bodies produce little or no insulin. Without insulin replacement, blood glucose can rise severely and DKA can develop. Untreated DKA can be fatal.

People with type 2 diabetes may produce insulin but have significant insulin resistance or gradually reduced insulin production. Some people with type 2 diabetes eventually require insulin treatment, while others can manage their blood glucose with lifestyle changes and/or non-insulin medicines.

Never stop prescribed insulin without speaking with your healthcare professional.

What are the side effects of insulin?

Insulin is an essential treatment for many people with diabetes, but it can cause side effects.

The most important is hypoglycemia, or low blood glucose, particularly when the insulin dose is greater than the body’s immediate needs.

Symptoms of low blood sugar can include:

• Shakiness
• Sweating
• Hunger
• Fast heartbeat
• Dizziness
• Irritability
• Confusion
• Weakness

Severe hypoglycemia can cause seizures or loss of consciousness and requires urgent treatment.

Other possible side effects include:

• Injection-site reactions
• Skin irritation
• Lipohypertrophy or lumps caused by repeatedly injecting in the same area
• Lipodystrophy, which can cause indentations
• Rare allergic reactions

Rotating injection sites can help reduce local skin complications.

Insulin and insulin resistance: what’s the difference?

These terms are often confused.

Insulin is a hormone.

Insulin resistance means the body’s cells do not respond as effectively to insulin as they should.

When insulin resistance develops, the pancreas may initially compensate by producing more insulin. Blood glucose can remain normal for some time.

Eventually, if the pancreas cannot produce enough insulin to overcome the resistance, blood glucose can rise and prediabetes or type 2 diabetes may develop.

This is why a normal blood sugar result does not necessarily mean that insulin sensitivity is perfect.

When should you get your insulin tested?

An insulin test isn’t routinely required for everyone.

A healthcare professional may consider insulin testing when investigating:

• Unexplained low blood sugar
• Suspected excessive insulin production
• Certain cases of insulin resistance
• How much insulin the pancreas is producing
• Some cases where diabetes type is unclear

Insulin is often interpreted alongside glucose and sometimes C-peptide. MedlinePlus notes that C-peptide can be particularly useful for assessing the body’s own insulin production because it remains in the blood longer than insulin.

If you have symptoms such as excessive thirst, frequent urination, unexplained weight loss, recurrent episodes of low blood sugar or persistently abnormal glucose readings, discuss appropriate testing with a healthcare professional.

Frequently asked questions about insulin

What is insulin in simple terms?

Insulin is a hormone made by the pancreas that helps glucose move from the blood into cells for energy. It also helps the body store and use nutrients after eating.

What organ produces insulin?

The pancreas produces insulin. The hormone is made by beta cells in the islets of Langerhans.

What is a normal insulin level?

There is no single normal insulin number for everyone. Results depend on whether you were fasting, the laboratory’s reference range, your glucose level and other clinical factors.

What happens when insulin levels are high?

High insulin may occur because the body is compensating for insulin resistance. Less commonly, it can be related to excessive insulin medication or conditions such as insulinoma. The significance depends heavily on the accompanying blood glucose level.

What happens when you lack insulin?

Insufficient insulin causes blood glucose to rise because glucose cannot be adequately used by cells. Severe insulin deficiency can lead to DKA.

Which foods increase insulin?

Carbohydrate-containing foods generally stimulate insulin release. Sugary and refined carbohydrate-rich foods can produce a rapid response, while protein can also stimulate insulin.

What is a bad insulin score?

There is no universally accepted “bad insulin score.” Fasting insulin, glucose and insulin-resistance calculations need to be interpreted in context.

What is a type 2 diabetes sugar level?

Diabetes can be diagnosed when fasting blood glucose is 126 mg/dL or higher, HbA1c is 6.5% or higher, or the 2-hour glucose during an OGTT is 200 mg/dL or higher, using appropriate diagnostic criteria and confirmation.

How do you check insulin levels?

Insulin is checked through a blood test. Depending on the reason for testing, your doctor may request fasting insulin, glucose, C-peptide or other tests.

Can you live without insulin?

No. People whose bodies produce little or no insulin, such as many people with type 1 diabetes, require insulin replacement to survive.

What are the side effects of insulin?

The most important side effect is low blood glucose. Injection-site reactions and changes in the fatty tissue beneath the skin can also occur. Rarely, allergic reactions may occur.

What foods cause too much insulin?

No individual food universally causes “too much insulin.” Rapidly absorbed carbohydrates can produce substantial insulin responses, while protein can also stimulate insulin secretion. Overall diet and metabolic health matter more than labelling one food as the cause.

Is high insulin curable?

High insulin can sometimes improve substantially when it is related to insulin resistance and the underlying factors are addressed. Other causes require specific medical treatment.

What is the normal insulin level by age?

There is no universally accepted age-specific insulin range for routine use. Your laboratory’s reference range and the circumstances of testing are important.

The bottom line

Insulin is essential for life. It allows the body to use glucose efficiently, helps regulate blood sugar and plays an important role in how the body stores and uses energy.

Both too little insulin and too much insulin can be associated with health problems, but an insulin result should never be interpreted on its own. Blood glucose, HbA1c, C-peptide, medications, diet, physical activity and the reason for testing can all influence how the result should be understood.

If you’re concerned about insulin resistance, high insulin, low insulin or diabetes, a healthcare professional can determine which tests are appropriate and interpret the results in the context of your overall health.

To get yourself tested at Sparsh Diagnostic Centre, call 9830117733.

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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

• Cleveland Clinic – Insulin: what it is, what it does and side effects
• CDC – Types of insulin
• MedlinePlus – Insulin in blood test
• American Diabetes Association – Diabetes diagnosis
• CDC – Diabetes testing