Diabetes: Symptoms, Types, Causes, Diagnosis & Treatment — Complete Guide
Updated: 6 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What Is Diabetes?
Diabetes is a group of diseases in which blood sugar builds up to dangerous levels because the body cannot supply enough insulin, the hormone that lets sugar enter cells for energy. Type 2 is most common. It causes no early pain but can damage the heart, nerves, kidneys, eyes and feet. Testing, monitoring, diet, activity and medicines help.
What the research says
Several approaches sharply cut the chance of prediabetes turning into type 2 diabetes. A network meta-analysis of 378 randomized trials with 113,122 adults with prediabetes found the largest reductions in new type 2 diabetes with dual GLP-1/GIP receptor agonists (relative risk 0.10, 95% CI 0.05–0.21), then GLP-1 receptor agonists (RR 0.26, 95% CI 0.19–0.40), closely followed by metformin plus intensive lifestyle intervention (RR 0.27, 95% CI 0.12–0.64). (Maria et al., Clin Transl Med, 2026) [3]
Strength training improves blood sugar control in type 2 diabetes. A meta-analysis of 33 randomized trials (1,396 middle-aged and older adults with type 2 diabetes) found resistance training lowered hemoglobin A1c by 0.62 percentage points and systolic blood pressure by 3.91 mmHg. (Zhang et al., Maturitas, 2026) [4]
After gestational diabetes, diet and exercise programs help weight and blood pressure, but proof of preventing type 2 diabetes is lacking. In 17 trials with 6,535 women with a history of gestational diabetes, interventions reduced weight (−0.89 kg), waist circumference (−0.79 cm), and systolic blood pressure (−1.60 mmHg) at about 12 months, with no significant effect on blood sugar outcomes or type 2 diabetes incidence. (Abdulsalam et al., Diabetes Res Clin Pract, 2026) [5]
TL;DR
Cause: the pancreas does not supply enough insulin, so glucose cannot enter cells and piles up in the blood
Types: type 1 (often starts young, quick onset), type 2 (most common, gradual), prediabetes (reversible), gestational (in pregnancy)
Symptoms: excessive thirst, frequent urination, unexplained weight loss, fatigue, blurry vision, slow-healing sores, frequent infections
Diagnosis: A1C test (6.5% or higher on two tests = diabetes), fasting blood sugar, random sugar, glucose tolerance test
Treatment: healthy eating, physical activity, blood sugar monitoring, insulin or oral drugs, and strict follow-up
Outlook: serious if ignored, but controllable — small daily steps protect your heart, nerves, kidneys, eyes, and feet
At a Glance
Item | Summary |
What it is | A group of diseases affecting how the body uses blood sugar (glucose), leading to excess sugar in the blood |
Primary types | Type 1 and type 2 (chronic); prediabetes and gestational diabetes (potentially reversible) |
Main cause | The pancreas does not produce enough insulin to move sugar into cells |
Typical symptoms | Excessive thirst, frequent urination, weight loss, fatigue, blurry vision, slow-healing sores |
Key test | A1C test — 6.5% or higher on two separate tests means diabetes |
Most common treatment | Healthy diet, physical activity, monitoring, and insulin or oral drugs depending on type |
Biggest risk | Heart disease, nerve, kidney, eye, and foot damage that develop gradually over time |
How insulin normally opens the cell door — and how each form of diabetes blocks it. Image: rinnit.com
What Is Diabetes?
Diabetes mellitus is a group of diseases that affect how your body uses blood sugar. Glucose is vital to your health because it is the main source of energy for the cells that make up your muscles and other tissues, and it is the brain's main fuel.
No matter which type you have, diabetes results in excess sugar in the blood. Too much sugar over time can cause serious health problems affecting the heart, blood vessels, kidneys, eyes, and nerves.
The chronic types are type 1 and type 2 diabetes. There are also potentially reversible conditions: prediabetes, when blood sugar is higher than normal but not high enough to be called diabetes, and gestational diabetes, which happens during pregnancy and may go away after the baby is born.
Type 1 diabetes can start at any age but often begins in childhood or the teen years, and its symptoms come on quickly and are more severe. Type 2 diabetes is the more common type, can develop at any age, and is more frequent in people over 40 — though type 2 in children is increasing. Importantly, some people with prediabetes, gestational diabetes, or type 2 may have no symptoms at all, which is why screening matters.
Diabetes Symptoms
Symptoms depend on how much blood sugar is elevated. Type 1 symptoms often appear suddenly and are more severe. The most common warning signs of type 1 and type 2 diabetes include:
Symptom | What it looks like |
Excessive thirst | Feeling more thirsty than usual |
Frequent urination | Urinating often |
Unexplained weight loss | Losing weight without trying |
Ketones in urine | Byproduct of muscle and fat breakdown when not enough insulin is available |
Fatigue and weakness | Feeling tired and weak |
Mood changes | Irritable or other mood changes |
Blurry vision | Vision becoming hazy or unclear |
Slow-healing sores | Cuts and wounds taking much longer than normal to heal |
Frequent infections | Lots of infections, such as gum, skin, and vaginal infections |
When to see a doctor: contact a healthcare provider if you or your child notice any of these signs. The sooner diabetes is diagnosed and treated, the better. After a diagnosis, close medical follow-up is needed until blood sugar levels stabilize.
How Insulin and Glucose Work
Understanding diabetes starts with understanding the normal process:
Insulin is a hormone released by a gland behind and below the stomach called the pancreas. It releases insulin into the bloodstream, and insulin circulates through the body, letting sugar enter cells and lowering the amount of sugar in the bloodstream. As blood sugar drops, the pancreas releases less insulin.
Glucose comes from two major sources: food and the liver. Sugar is absorbed into the bloodstream and enters cells with the help of insulin. The liver stores and makes glucose; when levels are low, such as after not eating for a while, the liver breaks down stored glycogen into glucose to keep levels in a typical range. In diabetes, this balance breaks down and sugar builds up instead.
The complete guide to diabetes at a glance — types, warning signs, diagnosis numbers, and control habits. Image: rinnit.com
Diabetes Causes
The exact cause of most types of diabetes is unknown. In all types, however, sugar builds up in the bloodstream because the pancreas does not produce enough insulin to let sugar reach the body's cells.
Both type 1 and type 2 may be caused by a combination of genetic or environmental factors. It is still unclear exactly what those factors are, which is why no one should blame themselves for developing diabetes.
Risk Factors
Family history plays a part in all types of diabetes. Beyond that, the risk factors differ by type:
Type | Risk factors |
Type 1 | Environmental factors and geography can add risk. Family members are sometimes tested for autoantibodies — destructive immune system cells associated with type 1. Having them increases risk, though not everyone with autoantibodies develops diabetes |
Type 2 | Race/ethnicity raises risk: Black, Hispanic, American Indian, and Asian American people are at higher risk. Being overweight or obese also increases risk |
Prediabetes and gestational | More common in people who are overweight or obese |
Diabetes Complications
Long-term complications develop gradually. The longer you have diabetes and the less controlled your blood sugar is, the higher your risk of complications. Eventually, complications can be disabling or even life-threatening. Prediabetes, if not addressed, can lead to type 2 diabetes.
Complication | What happens |
Heart and blood vessel disease | Coronary artery disease with chest pain (angina), heart attack, stroke, and narrowed arteries (atherosclerosis) |
Nerve damage (diabetic neuropathy) | Excess sugar injures the tiny blood vessels nourishing nerves, especially in the legs — causing tingling, numbness, burning, or pain starting at the toes and spreading upward. Damage to digestion nerves causes nausea, vomiting, diarrhea, or constipation. Men may experience erectile dysfunction |
Kidney damage (diabetic nephropathy) | Diabetes damages the tiny blood vessel clusters (glomeruli) that filter waste |
Eye damage (diabetic retinopathy) | Damage to the blood vessels of the eyes can lead to blindness |
Foot damage | Nerve damage or poor blood flow creates many foot complications |
Skin and mouth conditions | More prone to skin problems and bacterial and fungal infections |
Hearing impairment | More common in people with diabetes |
Alzheimer's disease | Type 2 diabetes may increase the risk of dementia such as Alzheimer's |
Depression | Common in people with both type 1 and type 2 diabetes |
Gestational diabetes carries its own set of risks for both mother and baby, including the baby growing too large (extra glucose crosses the placenta, triggering extra insulin and a large baby that may require a C-section), low blood sugar after birth, a higher risk of obesity and type 2 diabetes later in life, and in untreated cases, death before or shortly after birth. Mothers face higher odds of preeclampsia (high blood pressure, too much protein in urine, and swelling in the legs and feet) and of having gestational diabetes in the next pregnancy.
Prevention
Type 1 diabetes cannot be prevented. But the healthy lifestyle choices that treat prediabetes, type 2, and gestational diabetes also help prevent them:
Eat healthy foods. Choose foods lower in fat and calories and higher in fiber. Focus on fruits, vegetables, and whole grains, and aim for variety.
Get more physical activity. Aim for about 30 minutes of moderate aerobic activity most days of the week, or at least 150 minutes a week — for example, a brisk daily walk.
Lose excess pounds. Losing even 7% of your body weight can lower your risk. For a 200-pound (90.7 kg) person, that is 14 pounds (6.4 kg). During pregnancy, never try to lose weight — talk to your provider about healthy weight gain instead.
Sometimes drugs help. Metformin (Glumetza, Fortamet, others) may lower the risk of type 2 diabetes, but healthy lifestyle choices remain essential. If you have prediabetes, get your blood sugar checked at least once a year.
How Diabetes Is Diagnosed
Type 1 symptoms often begin suddenly, which is usually what prompts blood sugar testing. Because symptoms of the other types come on gradually or stay invisible, screening guidelines exist. The guidelines recommend screening for:
Anyone with a body mass index higher than 25 (23 for Asian Americans), regardless of age, who also has risk factors such as high blood pressure, non-typical cholesterol levels, an inactive lifestyle, a history of polycystic ovary syndrome or heart disease, or a close relative with diabetes
Anyone over age 35, with repeat screening every three years if results are normal
Women who have had gestational diabetes, screened every three years
Anyone diagnosed with prediabetes, tested every year
Anyone with HIV, who is advised to be tested
The four main tests for type 1, type 2, and prediabetes:
Test | How it works | Results that mean diabetes |
A1C test | No fasting needed; shows average blood sugar over the past 2–3 months by measuring the percentage of sugar attached to hemoglobin | 6.5% or higher on two separate tests; 5.7%–6.4% = prediabetes; below 5.7% = normal |
Random blood sugar test | Blood drawn at any time, regardless of meals | 200 mg/dL (11.1 mmol/L) or higher suggests diabetes |
Fasting blood sugar test | Blood drawn after an overnight fast | 126 mg/dL (7 mmol/L) or higher on two separate tests; 100–125 = prediabetes; below 100 = normal |
Glucose tolerance test | Fast overnight, measure fasting sugar, drink a sugary liquid, then test regularly for two hours | Over 200 mg/dL after two hours; 140–199 = prediabetes; below 140 = normal |
If type 1 is suspected, the provider may also test urine for ketones and run an autoantibody test to look for the destructive immune cells associated with type 1. During pregnancy, high-risk women are tested at the first prenatal visit, while average-risk women are screened during the second trimester.
Diabetes Treatment
Treatment depends on the type of diabetes, and blood sugar monitoring, insulin, and oral drugs may all be part of the plan. A healthy diet, healthy weight, and regular physical activity are important for managing every type.
Treatment for All Types
A diabetes diet is simply a healthy-eating plan: more fruits, vegetables, lean proteins, and whole grains, with fewer saturated fats, refined carbohydrates, and sweets. A registered dietitian can build a meal plan tailored to your goals, and carbohydrate counting is especially useful if you have type 1 or use insulin. Physical activity lowers blood sugar by moving sugar into cells for energy and making your body more sensitive to insulin. Aim for at least 30 minutes of moderate activity most days, or 150 minutes a week, and get up to move if you have been sitting more than 30 minutes.
Type 1 and Type 2 Diabetes
Treatment for type 1 diabetes involves insulin injections or an insulin pump, frequent blood sugar checks, and carbohydrate counting. For some people, a pancreas transplant or islet cell transplant may be an option.
Type 2 diabetes is mostly managed with lifestyle changes, blood sugar monitoring, and oral diabetes drugs, insulin, or both.
Monitoring: depending on the plan, blood sugar may be checked and recorded up to four times a day — more often when taking insulin. A continuous glucose monitor (CGM) tracks blood sugar every few minutes with a tiny sensor under the skin, reducing fingersticks and showing trends. Regular A1C testing measures your average over the past 2–3 months, and for most people the target is below 7%, adjusted for age and other conditions.
Insulin: people with type 1 must use insulin to survive, and many with type 2 or gestational diabetes also need it. Types include short-acting, rapid-acting, long-acting, and intermediate insulin, often combined for day and night use. Insulin cannot be taken orally because stomach enzymes destroy it, so it is injected with a fine needle, an insulin pen, or delivered by a pump. For type 1, FDA-approved hybrid closed loop systems link a CGM to a pump and adjust insulin automatically, though some user input (like reporting carbs) is still needed.
Oral and other drugs: some help the pancreas release more insulin; others stop the liver from producing glucose; others slow carbohydrate digestion or make tissues more sensitive to insulin. Metformin is generally the first drug prescribed for type 2 diabetes, and SGLT2 inhibitors prevent the kidneys from reabsorbing filtered sugar, which is then eliminated in the urine.
Transplantation and surgery: a pancreas transplant can eliminate the need for insulin, but transplants are not always successful and require lifetime immune-suppressing drugs with serious side effects, so they are usually reserved for people whose diabetes cannot be controlled or who also need a kidney transplant. Some people with type 2 diabetes and a BMI higher than 35 may benefit from bariatric surgery, such as gastric bypass, though long-term risks and benefits are still being studied.
Gestational Diabetes and Prediabetes
Gestational diabetes treatment centers on healthy eating, regular exercise, and blood sugar monitoring, with insulin or oral drugs in some cases; blood sugar is also monitored during labor. Prediabetes is usually treated with healthy lifestyle habits — exercising at least 150 minutes a week and losing about 7% of body weight may prevent or delay type 2 diabetes — plus medicines such as metformin for some people.
Emergency Warning Signs
Any type of diabetes can produce emergencies that need immediate care:
Emergency | What happens | Key symptoms |
High blood sugar (hyperglycemia) | Eating too much, illness, or not enough glucose-lowering medication | Frequent urination, excessive thirst, blurred vision, fatigue, headache, irritability |
Diabetic ketoacidosis (DKA) | Cells starved for energy cause the body to break down fat, producing toxic acids (ketones) in the blood; more common in type 1 | Nausea, vomiting, abdominal pain, sweet fruity breath, shortness of breath, dry mouth, weakness, confusion, coma |
Hyperosmolar syndrome | Very high blood sugar (over 600 mg/dL) turns the blood thick and syrupy; seen in type 2, often after illness | Dry mouth, extreme thirst, fever, drowsiness, confusion, vision loss, hallucinations |
Low blood sugar (hypoglycemia) | Skipping a meal, extra activity, or too much insulin or glucose-lowering medication | Sweating, shakiness, weakness, hunger, dizziness, headache, blurred vision, palpitations, confusion, fainting, seizures — treated quickly with fruit juice or glucose tablets |
Lifestyle and Home Remedies
Following your diabetes treatment plan takes total commitment, and careful management lowers the risk of serious complications:
Commit to managing your diabetes. Learn all you can, build a relationship with a diabetes educator, and ask your team for help when needed.
Choose healthy foods and stay at a healthy weight. Losing just 7% of body weight can improve blood sugar control in prediabetes and type 2. Emphasize fruits, vegetables, lean proteins, whole grains, and legumes, and limit saturated fat.
Make physical activity a daily routine. At least 30 minutes most days (150 minutes a week) plus two days of strength training controls blood sugar better than either exercise type alone. Get up and move at least every 30 minutes.
Identify yourself. Wear a tag or bracelet saying you have diabetes, keep a glucagon kit nearby, and make sure loved ones know how to use it.
Schedule yearly physicals and regular eye exams to screen for retinal damage, cataracts, and glaucoma.
Keep vaccinations up to date — a yearly flu shot, and pneumonia, COVID-19, and hepatitis B vaccines as your provider recommends.
Pay attention to your feet. Wash daily in lukewarm water, dry gently (especially between the toes), moisturize (not between toes), and check daily for blisters, cuts, sores, redness, or swelling.
Control blood pressure and cholesterol with diet, exercise, and drugs if needed.
Take care of your teeth. Brush and floss at least twice daily and keep up dental exams, since diabetes raises the risk of serious gum infections.
Quit smoking and tobacco. Smoking multiplies the risk of complications, and smokers with diabetes are more likely to die of cardiovascular disease than nonsmokers.
Drink alcohol responsibly — one drink a day for women, up to two for men, always with food, and check blood sugar before bed.
Take stress seriously. Stress hormones can block insulin from working properly, raising blood sugar. Set limits, prioritize tasks, use relaxation techniques, and get plenty of sleep.
A note on alternative medicine: some substances improve insulin processing in certain studies, while others show no benefit. Because the findings conflict, no alternative therapy is currently recommended for everyone. Never stop prescribed drugs or insulin without your provider's direction, and remember that no treatment — alternative or conventional — can cure diabetes.
Coping and Support
Living with diabetes can be difficult and frustrating. Even when you do everything right, blood sugar may rise — but sticking with your management plan usually shows a positive difference in your A1C at your next visit. Good management can feel overwhelming, so many people benefit from talking to a mental health professional or joining a support group. Support resources include the American Diabetes Association at 800-DIABETES (800-342-2383) and the Juvenile Diabetes Research Foundation at 800-533-CURE (800-533-2873).
Preparing for Your Appointment
You will likely start with your regular healthcare provider — or go straight to the emergency room if blood sugar is very high. Otherwise, you may be referred to an endocrinologist, and soon after diagnosis you will likely also meet a diabetes educator and a registered dietitian.
Before the appointment: ask about pre-appointment restrictions such as fasting; write down your symptoms, key personal information, stresses, allergies, and all medications, vitamins, and supplements; record your family history of diabetes, heart attacks, and strokes; bring home glucose readings with dates and times; bring a family member or friend; write down your questions; and note any prescription refills.
Helpful questions to ask your provider include whether your symptoms are related to diabetes, what tests you need, what else protects your health, what other management options exist, how to handle your other conditions together, whether you should see a dietitian or diabetes educator, and whether a generic alternative to prescribed medicine is available. Expect your provider to ask about your symptoms, how often and how severe they are, your family history of diabetes or preeclampsia, your diet, and your exercise habits.
Frequently Asked Questions
What are the 3 main types of diabetes?
The three main types are type 1 diabetes (the immune system stops insulin production, often starting in childhood), type 2 diabetes (cells resist insulin, the most common form), and gestational diabetes (developing during pregnancy). Prediabetes is a fourth, related condition in which blood sugar is higher than normal but not high enough to be called diabetes.
What are the first warning signs of diabetes?
The earliest signs usually include feeling thirstier than usual, urinating often, losing weight without trying, feeling tired and weak, blurry vision, slow-healing sores, and frequent infections such as gum, skin, or vaginal infections. If you notice these signs, see a doctor early — earlier diagnosis means sooner treatment.
What causes diabetes?
The exact cause of most types is unknown, but in all cases the pancreas does not produce enough insulin to move sugar into cells, so glucose builds up in the bloodstream. Both type 1 and type 2 likely result from a combination of genetic and environmental factors, and family history plays a part in every type.
How is diabetes diagnosed?
Diabetes is diagnosed with blood tests: an A1C of 6.5% or higher on two separate tests, a fasting blood sugar of 126 mg/dL or higher on two tests, a random blood sugar of 200 mg/dL or higher, or a two-hour glucose tolerance reading above 200 mg/dL. A1C results between 5.7% and 6.4% indicate prediabetes.
Is type 2 diabetes curable?
No treatment — alternative or conventional — can cure diabetes. However, prediabetes and gestational diabetes are potentially reversible, and type 2 can often be well controlled with weight loss, healthy eating, physical activity, and medicines. Exercising 150 minutes a week and losing about 7% of body weight can prevent or delay type 2 diabetes.
Can diabetes be prevented?
Type 1 diabetes cannot be prevented. Prediabetes, type 2, and gestational diabetes can often be prevented with healthy lifestyle choices: eating more fruits, vegetables, and whole grains, getting about 150 minutes of moderate activity a week, and losing excess weight. In some cases, medicines such as metformin also lower risk.
What should I do if my blood sugar is very high?
Very high blood sugar can cause diabetic ketoacidosis (nausea, vomiting, fruity breath, confusion — more common in type 1) or hyperosmolar syndrome (blood sugar over 600 mg/dL with confusion and vision loss — more common in type 2). Either situation needs care right away: contact your provider immediately or seek emergency medical care.
Conclusion
Diabetes is one of the most common serious conditions, but it is also one of the most manageable when caught early. The key lessons from this guide:
Silent at first: blood sugar can stay high for years without symptoms, so screening — especially after age 35 or with risk factors — is your best early-warning system.
Control is daily: a healthy diet, 150 minutes of weekly activity, monitoring, and prescribed medicines together keep blood sugar in a safe range.
Small habits protect big organs: the same daily steps that control sugar also protect your heart, nerves, kidneys, eyes, and feet.
This complete guide has walked you through the symptoms, causes, risk factors, diagnosis numbers, treatment options, and the home rules that make a real difference. Understanding your numbers is only the first step — keeping them healthy is a team effort with your provider.
You can also explore the full rinnit.com library for more evidence-based health guides.
Medical disclaimer: This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your healthcare provider with any questions about a medical condition. rinnit.com
References
Mayo Clinic Staff. Diabetes - Symptoms and causes. Mayo Clinic. January 21, 2026. https://www.mayoclinic.org/diseases-conditions/diabetes/symptoms-causes/syc-20371444
Mayo Clinic Staff. Diabetes - Diagnosis and treatment. Mayo Clinic. January 21, 2026. https://www.mayoclinic.org/diseases-conditions/diabetes/diagnosis-treatment/drc-20371451
Maria B, et al. Evidence-based ranking of diabetes prevention in prediabetes: A comprehensive network meta-analysis of 378 randomised controlled trials. Clin Transl Med. 2026;16(9):e70829. PMID 42711998. https://doi.org/10.1002/ctm2.70829
Zhang X, et al. The impact of resistance training on the Atherogenic index of plasma and cardiometabolic health-related indicators in middle-aged and older adults with type 2 diabetes: A systematic review and Meta-analysis. Maturitas. 2026;209:108935. PMID 41950771. https://doi.org/10.1016/j.maturitas.2026.108935
Abdulsalam R, et al. The effects of dietary and physical exercise interventions among women with a history of gestational diabetes mellitus on cardiometabolic risk: A systematic review and meta-analysis. Diabetes Res Clin Pract. 2026;237:113335. PMID 42184892. https://doi.org/10.1016/j.diabres.2026.113335
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