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Overview
What Is Diabetes Mellitus?
Diabetes mellitus is a group of conditions in which blood glucose, or blood sugar, stays too high over time. Insulin is a hormone that helps glucose move from the bloodstream into cells for energy; diabetes develops when the body makes too little insulin, cannot use it well, or both. Type 1, type 2 and gestational diabetes have different causes and biological mechanisms. Diabetes can affect people of all ages, although the likelihood and timing vary by type.
Symptoms
Diabetes Symptoms
- Increased thirst may occur as the body tries to remove extra glucose through urine.
- Frequent urination can result from high blood glucose drawing more water into the urine.
- Increased hunger may develop when glucose cannot enter cells efficiently for energy.
- Fatigue can occur when the body is not using glucose effectively.
- Blurred vision may result from changes in fluid levels in the eye.
- Unexplained weight loss is more common when insulin is severely lacking, especially in type 1 diabetes.
- Slow-healing cuts or sores may be a sign of prolonged high blood glucose.
- Recurring infections, including yeast or urinary infections, can occur in some people with diabetes.
How Symptoms Differ by Diabetes Type
WHEN TO ACT
Do not ignore persistent symptoms
Type 1 diabetes symptoms can appear quickly and may include marked thirst, frequent urination, vomiting, abdominal pain or rapid weight loss. Type 2 diabetes symptoms may develop gradually, and some people have few or no noticeable symptoms; gestational diabetes often has no obvious symptoms and is found through pregnancy screening. Arrange a clinical evaluation for persistent symptoms, unexplained weight loss, or repeated high glucose readings rather than trying to diagnose diabetes from symptoms alone.
Causes
What Causes Diabetes?
Diabetes develops when the body does not make enough insulin, cannot use insulin effectively, or both. As a result, glucose remains in the bloodstream instead of moving into cells for energy, causing persistently high blood glucose.
TYPE 1
Type 1 diabetes is an autoimmune condition in which the immune system attacks insulin-producing beta cells in the pancreas. It can begin in childhood or adulthood and requires insulin replacement.
TYPE 2
Type 2 diabetes usually involves insulin resistance, followed over time by reduced insulin production. Genetic factors, metabolic health, aging and lifestyle factors can all contribute.
GESTATIONAL
Gestational diabetes develops during pregnancy when hormonal changes increase insulin resistance beyond the body’s ability to compensate. It may resolve after birth but increases future risk of type 2 diabetes.
Diabetes is not caused simply by eating sugar. Individual causes can involve genetics, immune system factors, pregnancy-related hormonal changes and overall metabolic health; diet is only one part of the broader picture.
Risk Factors
Diabetes Risk Factors
| Less modifiable factors | Potentially modifiable or manageable factors |
|---|---|
| Family history of diabetes | Overweight or obesity, when present |
| Increasing age, particularly for type 2 diabetes | Physical inactivity |
| Certain racial or ethnic backgrounds | High blood pressure |
| History of autoimmune disease, for some type 1 diabetes risk | Abnormal cholesterol or triglyceride levels |
| Previous gestational diabetes or pregnancy-related risk | Prediabetes and related metabolic conditions |
Risk factors differ by diabetes type. Having one or more risk factors does not mean a person will develop diabetes, and some people develop diabetes without obvious risk factors.
Complications
Diabetes Complications
- Heart and blood vessel disease can increase the risk of heart attack, stroke and circulation problems.
- Kidney damage can develop when high blood glucose and blood pressure injure the kidneys over time.
- Eye disease, including damage to the retina, can threaten vision if not detected and treated.
- Nerve damage may cause pain, tingling, numbness or reduced sensation, especially in the feet.
- Foot problems can worsen when reduced sensation and poor circulation make injuries harder to notice or heal.
- Skin problems and recurrent infections may occur more often with diabetes.
- Gum disease and other dental problems can be more common when blood glucose is poorly controlled.
- Impaired immune function can make some infections more likely or slower to resolve.
Urgent Glucose-Related Complications
Diagnosis
How Diabetes Is Diagnosed
| Test | What it measures | Common use |
|---|---|---|
| A1C | Average blood glucose over roughly the previous 2–3 months | Diagnosing diabetes or prediabetes and monitoring longer-term control |
| Fasting plasma glucose | Blood glucose after at least 8 hours without food | Diagnosing diabetes or prediabetes |
| Oral glucose tolerance test | How the body handles glucose after a prescribed glucose drink | Diagnosing gestational diabetes or clarifying glucose regulation |
| Random plasma glucose | Blood glucose at any time, regardless of when a person last ate | Supporting diagnosis when symptoms of high blood glucose are present |
In general, diabetes is diagnosed with an A1C of 6.5% or higher, fasting plasma glucose of 126 mg/dL (7.0 mmol/L) or higher, a 2-hour oral glucose tolerance result of 200 mg/dL (11.1 mmol/L) or higher, or a random glucose of 200 mg/dL (11.1 mmol/L) or higher when symptoms are present. Prediabetes generally means an A1C of 5.7% to 6.4%, fasting glucose of 100 to 125 mg/dL (5.6 to 6.9 mmol/L), or a 2-hour result of 140 to 199 mg/dL (7.8 to 11.0 mmol/L). A clinician may repeat testing or use another test when appropriate.
Treatment & Management
Diabetes Treatment and Management
TYPE 1 DIABETES
Type 1 diabetes requires insulin replacement, along with glucose monitoring, nutrition planning, activity and education. Technology such as continuous glucose monitoring or an insulin pump may be appropriate for some people.
TYPE 2 DIABETES
Type 2 diabetes management may include balanced eating, physical activity, weight management when appropriate, oral or injectable medicines, and insulin when needed. Treatment also addresses blood pressure, cholesterol and other cardiovascular risks.
GESTATIONAL DIABETES
Gestational diabetes is managed with pregnancy-specific nutrition guidance, activity when safe, glucose monitoring and medicine or insulin when needed. Prenatal care and follow-up testing after delivery are important for parent and baby.
- Take prescribed diabetes medicines and use insulin when it is indicated.
- Monitor blood glucose as directed and record results when your care team recommends it.
- Choose balanced meals that fit your health needs, preferences and treatment plan.
- Include regular physical activity that is safe for your medical condition.
- Consider weight management when appropriate and with supportive clinical guidance.
- Keep recommended vaccinations up to date because infections can affect glucose control.
- Attend routine screenings for the eyes, kidneys, feet, nerves, heart and blood vessels.
PERSONALIZED CARE
Follow an individualized treatment plan
Do not change medicines, stop insulin or alter insulin doses without guidance from your diabetes care team. Glucose targets and treatment choices should reflect your diabetes type, health conditions, pregnancy status and risk of low blood glucose.
Prevention & Screening
Diabetes Prevention and Screening
Type 2 diabetes risk may be lowered through regular physical activity, nutritious eating, weight management when appropriate, adequate sleep and treatment of related conditions such as high blood pressure. These steps do not guarantee prevention. Type 1 diabetes cannot currently be prevented through lifestyle changes.
- Adults with risk factors such as overweight, family history, prediabetes or a history of gestational diabetes should discuss screening with a clinician.
- Adults in age ranges recommended by current clinical guidance may benefit from routine diabetes or prediabetes screening.
- People who had gestational diabetes should receive postpartum testing and ongoing screening as advised.
- Children and adolescents with overweight or obesity plus relevant risk factors should be assessed for screening needs.
- Anyone with symptoms or an abnormal previous result should ask a clinician whether testing is appropriate.
Screening intervals depend on age, previous results, pregnancy status and personal risk. Follow current guidance from your clinician or public health program rather than relying on a single fixed schedule.
Outlook and Prognosis
Outlook and Prognosis for Diabetes
Diabetes is usually a chronic condition requiring ongoing management. Outcomes vary according to the diabetes type, glucose control, other health conditions, access to care and how consistently the treatment plan can be followed. Gestational diabetes often improves after pregnancy, but it can increase future type 2 diabetes risk.
When Should You See a Doctor
When Should You See a Doctor for Diabetes?
- Arrange medical evaluation for persistent thirst, frequent urination, unexplained weight loss, fatigue or other possible diabetes symptoms.
- Discuss an abnormal screening result with a clinician, even if you feel well.
- Seek advice for repeated high glucose readings, especially when they are outside your prescribed target range.
- Contact your pregnancy care team about diabetes symptoms, abnormal glucose results or concerns about gestational diabetes.
- Ask for help if known diabetes is becoming difficult to manage or you are having repeated high or low glucose readings.
SEEK URGENT HELP
Severe symptoms need immediate attention
Seek urgent or emergency care for severe confusion, fainting, trouble breathing, persistent vomiting, severe dehydration, inability to keep fluids down or other signs of a serious glucose emergency. Do not drive yourself if you are confused, faint or severely unwell.
Branches
2 topics
Diabetes Mellitus
Bariatric & Metabolic Medicine
Diabetes Mellitus
Endocrinology & Metabolic Diseases
