Diabetes mellitus: Symptoms, risk factors, types, and treatment of Diabetes

According to the 2025 International Diabetes Federation (IDF) Diabetes Atlas, approximately 589 million adults (aged 20-79 years) worldwide live with diabetes, which is more than 10% of the world’s adult population.¹

By 2050, IDF projections show that 1 in 8 adults, or approximately 853 million, will be living with diabetes, an increase of 45%.²  These projections highlight the urgent need for continued awareness, prevention, and access to diabetes management worldwide. 

In Sub-Saharan Africa, more than 24.6 million people are currently living with diabetes. By 2050, the region is expected to experience the highest increase in the number of people with diabetes, with a projected growth rate of 142%.¹

Early detection of diabetes is key. Diabetes can pave the way for a variety of other health issues, such as blindness, heart disease, nerve damage, and kidney failure.^3,4 That's why it’s important to understand what diabetes is as well as the various types, causes, symptoms, and contributing risk factors.

Contact your doctor or healthcare professional if you think you might have diabetes or are experiencing diabetes-related complications.

Diabetes mellitus, or diabetes, is a chronic health condition that develops when the body can't produce 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 that develops 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, serving as the primary source of energy for your body, and can be consumed in various 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, where it can 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.¹ 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 preventive action.^9,10 Type 1 and type 2 diabetes share similar symptoms, including:³

• 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 symptoms can be mild or absent, so people with type 2 diabetes can live several years with the condition before being diagnosed.¹

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 are¹¹:

• 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.¹² Once a person has type 1 diabetes, they need 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.¹² In 2021, 8.75 million people were living with type 1 diabetes worldwide.¹³

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.¹³

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, resulting in the inability to produce insulin.¹² 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 recognized by symptoms such as:¹²

• 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.¹² 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 testing your blood sugar and carefully adjusting your food and insulin intake, you can maintain blood glucose levels within a safe range and help prevent long-term health problems that can result from prolonged 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.¹²

Working closely with a healthcare team is key to managing diabetes properly and avoiding some of the issues that can occur when blood sugar is not kept in a safe range. High or low blood sugar levels can be dangerous, and over time, high blood sugar can lead to a wide range of conditions affecting the eyes, hands, feet, heart, and other organs.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, occurring when the body fails to use insulin properly and the pancreas doesn't produce enough insulin to maintain healthy blood glucose levels.^3,6,14 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.¹⁵ 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.¹⁴ The key contributors to the rise in type 2 diabetes include:¹⁶

• Urbanization
• 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 condition is known as 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, resulting in even less insulin production. Without enough insulin, glucose remains in the blood, leading to high blood sugar levels, known as hyperglycemia.

Type 2 diabetes symptoms

Type 2 diabetes symptoms can develop slowly, making them hard to spot.¹⁴ 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.^17,18

Common type 2 diabetes symptoms include:³

• 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.^14,15 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.^1,15

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:^14,15

• 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 control 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.¹⁹

It's essential to work closely with your healthcare team to determine the most suitable 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.²⁰ That's why it's important to manage diabetes with lifestyle changes, oral medications, or insulin.¹⁹ In most cases, type 2 diabetes treatment involves making changes to your diet and lifestyle.

Diabetes is a progressive disease, so it may take more intervention for you to meet your target blood glucose levels as you age.²¹

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.^22,23

LADA develops in people over 30 and 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 specialized treatment.

LADA accounts for 2-12% of all cases of adult-onset diabetes, but this figure varies greatly depending on demographics and screening methods.^22,23

Research suggests that up to 10% of people diagnosed with type 2 may actually have LADA.²⁴

Gestational diabetes (GDM), or “pregnancy diabetes,"  is a type of diabetes that might develop during the course of a pregnancy.²⁵ 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 2024, about 23 million, or nearly 19.7% of live births worldwide, had some form of hyperglycemia during pregnancy.² Gestational diabetes is more common in low and middle-income countries with limited access to maternal care.²⁶

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 ^3,15,26

Learn more about gestational diabetes and managing diabetes and pregnancy in the article, “Guide to a healthy pregnancy with diabetes and gestational diabetes”.

Depending on the type of diabetes you have, your doctor or healthcare team might advise you about diet and lifestyle changes. Treatments for diabetes can vary depending on the individual and may include oral medication, insulin, dietary changes, and regular physical activity. Your healthcare provider will likely explain how to test your blood sugar and other aspects of diabetes self-management, such as maintaining a healthy weight through a balanced diet and regular exercise.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 they have. 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 alternative site testing with your doctor or healthcare team to see 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 provider 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.

Sources:

1. IDF Diabetes Atlas [Internet]. International Diabetes Federation. 2025 [cited 2025 Jul 9]. Available from: https://www.diabetesatlas.org
2. Global diabetes data report 2000- 2045 [Internet]. International Diabetes Federation. 2025 [cited 2025 Jul 9]. Available from: https://diabetesatlas.org/data/
3. Diabetes [Internet]. World Health Organization. 2023 Apr 5 [cited 2025 Jul 9]. Available from: https://www.who.int/news-room/fact-sheets/detail/diabetes
4. Li Y, Liu Y, Liu S, et al. Diabetic vascular diseases: molecular mechanisms and therapeutic strategies. Signal Transduct Target Ther. 2023;8(1):152.
5. Ilonen J, Lempainen J, Veijola R. The heterogeneous pathogenesis of type 1 diabetes mellitus. Nat Rev Endocrinol. 2019;15(11):635-650.
6. DeFronzo RA, Ferrannini E, Groop L, et al. Type 2 diabetes mellitus. Nat Rev Dis Primer. 2015;1(1):15019.
7. Campos V, Tappy L, Bally L, Sievenpiper JL, Lê KA. Importance of Carbohydrate Quality: What Does It Mean and How to Measure It? J Nutr. 2022;152(5):1200-1206.
8. Li M, Chi X, Wang Y, Setrerrahmane S, Xie W, Xu H. Trends in insulin resistance: insights into mechanisms and therapeutic strategy. Signal Transduct Target Ther. 2022;7(1):216.
9. Uusitupa M, Khan TA, Viguiliouk E, et al. Prevention of Type 2 Diabetes by Lifestyle Changes: A Systematic Review and Meta-Analysis. Nutrients. 2019;11(11):2611.
10. Felton JL, Griffin KJ, Oram RA, et al. Disease-modifying therapies and features linked to treatment response in type 1 diabetes prevention: a systematic review. Commun Med. 2023;3(1):130.
11. Ismail L, Materwala H, Al Kaabi J. Association of risk factors with type 2 diabetes: A systematic review. Comput Struct Biotechnol J. 2021;19:1759-1785.
12. DiMeglio LA, Evans-Molina C, Oram RA. Type 1 diabetes. Lancet Lond Engl. 2018;391(10138):2449-2462.
13. Gregory GA, Robinson TIG, Linklater SE, et al. Global incidence, prevalence, and mortality of type 1 diabetes in 2021 with projection to 2040: a modelling study. Lancet Diabetes Endocrinol. 2022;10(10):741-760.
14. Type 2 Diabetes [Internet]. International Diabetes Federation. 2025 [cited 2025 Jul 9]. Available from: https://idf.org/about-diabetes/type-2-diabetes/
15. ElSayed NA, Aleppo G, Aroda VR, et al. 2. Classification and Diagnosis of Diabetes: Standards of Care in Diabetes—2023. Diabetes Care. 2022;46(Supplement_1):S19-S40.
16. Facts & figures [Internet]. International Diabetes Federation. 2025 [cited 2025 Jul 9]. Available from: https://idf.org/about-diabetes/diabetes-facts-figures/
17. Clare L Gillies, Paul C Lambert, Keith R Abrams, et al. Different strategies for screening and prevention of type 2 diabetes in adults: cost effectiveness analysis. BMJ. 2008;336(7654):1180.
18. Ogurtsova K, Guariguata L, Barengo NC, et al. IDF diabetes Atlas: Global estimates of undiagnosed diabetes in adults for 2021. Diabetes Res Clin Pract. 2022;183:109118.
19. ElSayed NA, Aleppo G, Aroda VR, et al. 5. Facilitating Positive Health Behaviors and Well-being to Improve Health Outcomes: Standards of Care in Diabetes—2023. Diabetes Care. 2022;46(Supplement_1):S68-S96.
20. Tomic D, Shaw JE, Magliano DJ. The burden and risks of emerging complications of diabetes mellitus. Nat Rev Endocrinol. 2022;18(9):525-539.
21. ElSayed NA, Aleppo G, Aroda VR, et al. 13. Older Adults: Standards of Care in Diabetes—2023. Diabetes Care. 2022;46(Supplement_1):S216-S229.
22. Redondo MJ, Morgan NG. Heterogeneity and endotypes in type 1 diabetes mellitus. Nat Rev Endocrinol. 2023;19(9):542-554.
23. Buzzetti R, Tuomi T, Mauricio D, et al. Management of Latent Autoimmune Diabetes in Adults: A Consensus Statement From an International Expert Panel. Diabetes. 2020;69(10):2037-2047.
24. Mishra R, Hodge KM, Cousminer DL, Leslie RD, Grant SFA. A Global Perspective of Latent Autoimmune Diabetes in Adults. Trends Endocrinol Metab. 2018;29(9):638-650.
25. McIntyre HD, Catalano P, Zhang C, Desoye G, Mathiesen ER, Damm P. Gestational diabetes mellitus. Nat Rev Dis Primer. 2019;5(1):47.
26. About Gestational Diabetes [Internet]. International Diabetes Federation. 2025 [cited 2025 Jul 9]. Available from: https://idf.org/about-diabetes/gestational-diabetes/
27. ElSayed NA, Aleppo G, Aroda VR, et al. 1. Improving Care and Promoting Health in Populations: Standards of Care in Diabetes—2023. Diabetes Care. 2022;46(Supplement_1):S10-S18.