Diabetes: Types, Symptoms, Diagnosis and Treatment

Diabetes means blood glucose is too high because the body makes too little insulin, uses it poorly, or both. In the US about 1 in 9 adults has diabetes and more than 1 in 3 has prediabetes — many without knowing it.

Types of diabetes

Type	What happens	Share
Type 2	Insulin resistance plus declining insulin production; strongly linked to weight, inactivity and genetics	about 90–95%
Type 1	Autoimmune destruction of insulin-producing cells; insulin needed for life	about 5–10%
LADA	Slowly progressing autoimmune diabetes in adults, often first mistaken for type 2	a few % of adult cases
Gestational	Diabetes first appearing in pregnancy	roughly 6–9% of pregnancies in the US
Other	Monogenic forms (MODY), after pancreatitis or surgery, cystic fibrosis, medication-induced (e.g. steroids)	small

Risk factors for type 2 diabetes

Overweight, especially around the waist
Physical inactivity
Age 35 and older (but rising in younger people)
Family history of diabetes
Prediabetes, previous gestational diabetes, polycystic ovary syndrome
High blood pressure, low HDL or high triglycerides
Higher risk in Black, Hispanic/Latino, American Indian, Alaska Native, Asian American and Pacific Islander populations

Symptoms

Type 2 diabetes often causes no symptoms for years. When glucose is clearly high: thirst, frequent urination, tiredness, blurred vision, slow-healing wounds, frequent infections, tingling feet. Type 1 usually starts quickly over weeks, with weight loss and sometimes ketoacidosis.

Diagnosis

Any one of these, confirmed by a second abnormal result: fasting glucose 126 mg/dL or more · HbA1c 6.5% or more · 2-hour OGTT 200 mg/dL or more. Or a random glucose of 200 mg/dL or more with classic symptoms. The ADA recommends screening all adults from age 35, and earlier with risk factors. Details: lab tests explained.

Complications

Long-term high glucose damages blood vessels and nerves: heart attack and stroke, kidney disease, eye disease (retinopathy), nerve damage and foot ulcers, gum disease and erectile dysfunction. Acute complications are very low blood sugar (with treatment) and very high blood sugar with ketoacidosis or hyperosmolar state. Good control of glucose, blood pressure and cholesterol, plus not smoking, prevents most of this.

Treatment

Lifestyle: healthy eating, regular activity, weight management, sleep — the foundation for every type.
Type 2 medicines: metformin; GLP-1 receptor agonists and dual GIP/GLP-1 agonists (also strong for weight); SGLT2 inhibitors (also protect heart and kidneys); DPP-4 inhibitors; insulin when needed.
Type 1 and LADA: insulin, increasingly with pumps and automated insulin delivery systems linked to a CGM.
Education and support: diabetes self-management education (DSMES) improves outcomes.

Prevention

Type 2 diabetes can often be prevented or delayed: in the Diabetes Prevention Program, losing about 7% of body weight and 150 minutes of weekly activity cut the risk by 58%. See How to Prevent Type 2 Diabetes. Type 1 diabetes cannot currently be prevented, though screening for autoantibodies in relatives allows early detection.

Educational content only; not medical advice. Follow the treatment plan you have agreed with your doctor or diabetes team. In an emergency, call 911 (US) or your local emergency number.