Diabetes Mellitus: Symptoms, Types, and Treatment

Diabetes mellitus, or diabetes, is a chronic health condition that develops when the body can't make enough or any insulin, combined with the body's inability to use insulin effectively, leading to excess glucose, or sugar, in the blood.^5,6

There are several main types of diabetes:

• Type 1
• Type 2
• Latent Autoimmune Diabetes in Adults (LADA) or Type 1.5
• Gestational Diabetes (diabetes during pregnancy)

Blood sugar (glucose) and insulin 

To better understand diabetes, it’s important first to learn where insulin comes from and how the body uses it to manage blood glucose levels.

Insulin and glucose work together to provide your body with energy from the food and drinks you consume. 

Glucose is a type of sugar found in your blood, and is the main source of energy for your body, and can be consumed in different forms.⁷ 

Insulin is a hormone produced by your pancreas that allows the glucose in your blood to enter your cells and be used as energy.⁸

Here’s how it happens:

1. Your body converts carbohydrates (sugars and starches) into glucose.⁷
2. Glucose enters your bloodstream and is carried throughout your body (hence the terms "blood glucose" and "blood sugar").
3. Insulin allows blood glucose to enter your cells and be broken down for energy.⁸

People with diabetes still have glucose in their bloodstream from carbohydrate consumption, but it cannot enter their cells because their pancreas does not produce any or enough insulin, and it is used ineffectively. This causes glucose to remain in your bloodstream, resulting in high blood sugar levels. 

There is no one cause of diabetes.^5,6 What causes diabetes is different for every individual. Everyone has different lifestyles, habits, and genetic factors that could contribute to the condition. 

In type 1 diabetes, the immune system destroys insulin-producing beta cells in the pancreas.⁵ With type 2 diabetes, a variety of factors, like genetics and lifestyle, can contribute as causes.⁶ 

Knowing the risk factors and early warning signs of diabetes can help you take preventative action.^9,10 Type 1 and type 2 diabetes share similar symptoms, including³:

• Excessive thirst and dry mouth
• Frequent urination
• Lack of energy, tiredness
• Slow healing wounds
• Recurrent infections in the skin
• Blurred vision
• Tingling or numbness in hands and feet

These systems can be mild or absent, so people with type 2 diabetes can go undiagnosed for years if they do not have symptoms or their symptoms are missed.¹¹

Contact your doctor or healthcare professional if you think you have noticed signs of diabetes so that you can begin treatment right away.

Risk factors for diabetes

Although there are risk factors that can increase a person's chances of developing diabetes, having these factors does not guarantee diabetes. Some common risk factors for diabetes are¹²:

• Lack of physical activity
• Obesity
• Smoking
• Infections
• Gestational diabetes
• Age
• Family history

Type 1 diabetes is an autoimmune disease.⁵ If you are diagnosed with type 1 diabetes, then that means your pancreas does not produce insulin. Scientists aren't sure why, but the immune system destroys the insulin-producing beta cells in the pancreas.

Contrary to popular belief, eating sugar is not the cause of type 1 diabetes. 

People with type 1 diabetes need to take insulin via injections or an insulin pump to "unlock" their cells to access the glucose in their bloodstream and break it down into energy.¹³ Once a person has type 1 diabetes, they need to inject insulin to live, no matter what they eat or do.

The number of people diagnosed with type 1 diabetes is increasing annually by 2-3% on a global scale.¹³ In 2021, 8.75 million people were living with type 1 diabetes worldwide.¹⁴

Type 1 diabetes (T1D)  was previously known as "juvenile diabetes" because it primarily affected children, but it is now known that it can affect people at any age. In fact, according to the 2022 T1D Index, 62% of all new T1D cases in 2022 were in people aged 20 years or older.¹⁴

Type 1 diabetes causes

Type 1 diabetes is believed to be caused by the body’s immune cells mistakenly attacking and destroying the insulin-producing beta cells in the pancreas, which means they can no longer produce insulin.¹³ A complex mix of genetics, viruses, and environmental factors can also contribute to it.

Type 1 Diabetes symptoms

Type 1 diabetes is common in children and young adults and can be recognised by symptoms such as¹³:

• frequent urination
• excessive thirst
• weight loss

Keep in mind that some of these symptoms may not be present, and the diagnosis may be delayed or missed entirely. This is why it’s important to check for diabetes as a precaution. 

For adults, the symptoms may vary and can be misclassified as type 2 diabetes.¹³ In fact, almost half of type 1 cases in adults are misclassified as type 2 diabetes. 

Type 1 diabetes treatment

Treatment for type 1 diabetes requires insulin. By regularly checking blood sugar and calibrating food and insulin carefully, you can keep blood glucose levels in a safe range and help head off long-term health problems that can result from extended periods of high blood sugar.⁴

Living with type 1 diabetes

Insulin therapy isn't a cure for type 1 diabetes, as it simply replaces the insulin that a healthy pancreas would naturally make.

People with type 1 diabetes can manage their daily lives by monitoring blood sugar levels, balancing diet and exercise with insulin, and learning how lifestyle choices affect their bodies.¹³

Working closely with a healthcare team is key to managing diabetes properly and avoiding some of the issues that can occur if blood sugar isn't kept in a safe range. Too high or low blood sugar levels can be dangerous, and over the years, high blood sugar can lead to a wide range of conditions affecting the eyes, hands, feet, heart, and more.⁴

Just because you have type 1 diabetes does not mean you will have all of these problems. A healthy lifestyle, a good diabetes management plan, and a supportive healthcare team can help you live a fulfilling life with type 1 diabetes.

Type 2 diabetes is the most common form of diabetes and occurs when the body doesn't use insulin properly and the pancreas doesn't create enough insulin to maintain healthy blood glucose levels.^3,6,15 It can be treated through lifestyle changes, medication, or insulin.

Type 2 diabetes used to be called "adult onset" diabetes, but new research shows that it can affect children too.¹⁶ Still, type 2 diabetes is mainly diagnosed in adults. And because it often presents with few symptoms, type 2 diabetes can progress for many years without being diagnosed.

Over 90% of people with diabetes around the world have type 2 diabetes, which is driven by socio-economic, demographic, environmental, and genetic factors.¹⁵ The key contributors to the rise in type 2 diabetes include¹⁷:

• Urbanisation
• An aging population
• Decreasing levels of physical activity
• Increasing overweight and obesity prevalence

Insulin resistance

In type 2 diabetes, your body doesn't respond to insulin as it should; this is called insulin resistance.⁶ Insulin resistance causes blood sugar levels to rise, which makes the beta cells of the pancreas produce more insulin. This can exhaust the beta cells, which means it produces even less insulin. Without enough insulin, glucose stays in the blood, leading to high blood sugar levels, called hyperglycaemia.

Type 2 diabetes symptoms

Type 2 diabetes symptoms can develop slowly, making them hard to spot.¹⁵ About half of people with type 2 diabetes do not know they have it, and 20 to 30% already have problems before they are diagnosed.^18,19 

Common type 2 diabetes symptoms include³:

• Frequent thirst or urination
• Hunger, even when you're eating enough
• Fatigue
• Blurred vision
• Cuts or bruises that heal slowly
• Tingling, pain, or numbness in your hands or feet

Type 2 diabetes causes 

The causes of type 2 diabetes are not fully understood.⁶

Extra weight can cause insulin resistance, so being overweight or physically inactive can contribute to type 2 diabetes.^15,16 Excess body fat, particularly around the abdomen, can increase the risk of developing type 2 diabetes in people who do not meet the definition of being overweight or obese.¹⁶ 

Type 2 diabetes risk factors

Being overweight and not being physically active can be linked to type 2 diabetes, but there are other factors that can increase the risk. Additional risk factors for type 2 diabetes include^15,16:

• Age
• Ethnicity
• Family history of diabetes
• High blood pressure or cholesterol
• Prior gestational diabetes

Living with type 2 diabetes

You may find that you can manage your blood glucose levels by changing your eating habits and increasing physical activity, or you may need medication to help keep your glucose levels within a safe range.²⁰

It's important to work closely with your healthcare team to determine the best treatment for you, and then follow it. Preventing ongoing high blood sugar can help you avoid long-term problems with your eyes, kidneys, heart, and the nerves in your feet and hands.⁴

Type 2 diabetes treatment

High levels of sugar in your blood can result in a wide range of health issues.²¹ That's why it's important to manage diabetes with lifestyle changes, oral medications, or insulin.²⁰ In most cases, type 2 diabetes treatment involves diet and lifestyle changes.

Diabetes is a progressive disease, so it may take more intervention for you to meet your target blood glucose levels as you age.²²

Latent autoimmune diabetes in adults (LADA) is a type of diabetes that shares characteristics with both type 1 and type 2 diabetes and is often called 1.5 diabetes.^23,24 

LADA develops in people over the age of 30, and it is classified as a slowly progressive form of autoimmune diabetes in which the body's immune system mistakenly attacks insulin-producing beta cells in the pancreas. Type 2 diabetes symptoms, such as insulin resistance and obesity, may accompany this condition.

People with LADA are often initially misdiagnosed with type 2 diabetes, but because LADA is an autoimmune disease, it requires specialised treatment. 

LADA accounts for 2-12% of all cases of adult-onset diabetes, but this figure varies greatly depending on demographics and screening methods. ^23,24

Research suggests that up to 10% of people diagnosed with type 2 may actually have LADA.²⁵

Gestational diabetes (GDM), or "pregnancy diabetes,"  is a type of diabetes that might develop during the course of a pregnancy.²⁶ Gestational diabetes is defined by high blood glucose levels caused by the body's inability to produce enough insulin to allow cells to absorb glucose.

In 2025, about 23.3 million, or nearly 15.6% of live births worldwide, had some form of hyperglycaemia during pregnancy.² Gestational diabetes is more common in low and middle-income countries with limited access to maternal care.²⁷

Gestational diabetes usually goes away after the baby is born, but can increase the risk of type 2 diabetes later in life for both the birth mother and the baby.^3,16,27

Most people check their blood sugar by pricking a finger to apply a small drop of blood to a test strip, depending on the type of diabetes. The test strip is then inserted into a measuring device called a blood glucose meter. 

Continuous glucose monitoring (CGM) systems are another way to monitor blood sugar levels. These systems work differently depending on the type you use, but they all help track your sugar levels over time.

Some blood glucose meters allow you to test with blood from places other than your fingertips. Discuss alternate site testing with your doctor or healthcare team to find out if this could be an option for you. 

Millions of people worldwide live with diabetes and face unique sets of challenges. Get in touch with your healthcare professional if you or someone you know is showing diabetes symptoms. Diabetes is not your fault or something to be blamed for - it's an unexpected change you can learn to help manage. Although a diabetes diagnosis can be overwhelming at first, there are many resources and management options available. By being proactive, making lifestyle changes, and collaborating with your healthcare team, you can learn how to live well while managing diabetes.

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