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Type 2 Diabetes Mellitus (T2DM)

Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and progressive pancreatic beta-cell dysfunction, resulting in persistent hyperglycemia

Also called

Non-insulin-dependent diabetes mellitus (NIDDM)

ICD-10

E11

Specialty

Endocrine

Onset

Chronic

Reviewed

August 2026

On This Page

Overview

  • Type 2 Diabetes Mellitus (T2DM) is the most common form of diabetes. It develops when body tissues become resistant to insulin and the pancreatic beta cells progressively fail to produce sufficient insulin.
  • It is strongly associated with overweight/obesity, physical inactivity, family history, and increasing age, although it can occur in younger people.

Etiology & Risk Factors

-Etiology:

Type 2 Diabetes Mellitus (T2DM)  results from a combination of:

  • Insulin resistance
  • Progressive pancreatic beta-cell dysfunction
  • Inappropriate hepatic glucose production
  • Genetic susceptibility
  • Environmental and lifestyle factors

-Insulin resistance commonly affects:

  • Skeletal muscle
  • Liver
  • Adipose tissue

-Inheritance

Type 2 Diabetes Mellitus has a strong genetic component, but it does not follow a simple Mendelian inheritance pattern.

-Family history substantially increases risk.

-Risk Factors

  • Overweight or obesity
  • Central obesity
  • Physical inactivity
  • Family history of Type 2 Diabetes Mellitus (T2DM)
  • Increasing age
  • History of gestational diabetes
  • Previous prediabetes
  • Hypertension
  • Dyslipidemia
  • Cardiovascular disease
  • Polycystic ovary syndrome

Pathophysiology

Genetic susceptibility + environmental factors → autoimmune activation → pancreatic beta-cell destruction → progressive loss of insulin secretion → absolute insulin deficiency → decreased peripheral glucose uptake + increased hepatic glucose production → hyperglycemia → increased lipolysis → ketone production → risk of diabetic ketoacidosis

Clinical Presentation

-Symptoms

Many patients are initially asymptomatic.

-When symptoms occur:

  • Polyuria
  • Polydipsia
  • Increased hunger
  • Fatigue
  • Blurred vision
  • Unintentional weight loss
  • Recurrent infections
  • Pruritus, particularly genital itching
  • Slow wound healing
  • Recurrent urinary or skin infections
  • Numbness or tingling in the extremities

-Signs

  • Overweight or obesity
  • Central adiposity
  • Hypertension
  • Acanthosis nigricans
  • Reduced peripheral pulses in peripheral arterial disease
  • Visual abnormalities due to diabetic retinopathy

-Severe Disease

Poorly controlled Type 2 Diabetes Mellitus (T2DM) can lead to:

  • Hyperosmolar hyperglycemic state (HHS)
  • Severe dehydration
  • Electrolyte abnormalities

History Taking

-Ask about:

  • Polyuria
  • Polydipsia
  • Polyphagia
  • Weight change
  • Fatigue
  • Blurred vision
  • Recurrent infections
  • Slow wound healing
  • Foot pain or ulcers
  • Symptoms of cardiovascular disease
  • Symptoms of peripheral arterial disease
  • Symptoms of kidney disease
  • Previous gestational diabetes
  • Family history of diabetes

Physical Examination

-General Examination

  • Weight
  • Body mass index
  • Waist circumference
  • Blood pressure
  • Hydration status
  • General nutritional status

Look for:

  • Central obesity
  • Acanthosis nigricans
  • Skin tags
  • Evidence of infection

System-Specific Examination

-Cardiovascular:

  • Blood pressure
  • Peripheral pulses
  • Signs of coronary artery disease
  • Signs of heart failure

Neurological:

  • Peripheral sensation
  • Vibration and proprioception when appropriate
  • Reflexes
  • Assessment for diabetic peripheral neuropathy

Feet:

  • Skin integrity
  • Ulcers
  • Calluses
  • Deformities
  • Peripheral pulses
  • Monofilament sensation
  • Evidence of infection

-Eyes:

  • Visual acuity
  • Retinal examination for diabetic retinopathy

Investigations

-Biochemistry / Specific Tests

-Fasting Plasma Glucose

  • ≥126 mg/dL (7.0 mmol/L) is diagnostic of diabetes when confirmed appropriately.

–HbA1c

  • ≥6.5% is diagnostic of diabetes when measured using an appropriate standardized laboratory method.
  • Reflects average glycemic exposure over approximately 2–3 months.

–A 2-hour plasma glucose level of:

  • ≥200 mg/dL (11.1 mmol/L) after a 75-g oral glucose load indicates diabetes.

-Random Plasma Glucose

  • ≥200 mg/dL (11.1 mmol/L) in a patient with classic symptoms of hyperglycemia or hyperglycemic crisis supports the diagnosis.

–Additional investigations

  • Serum creatinine and estimated glomerular filtration rate
  • Urine albumin-to-creatinine ratio
  • Lipid profile
  • Liver function tests
  • Electrolytes
  • Ketones when clinically indicated

Diagnosis

Type 2 Diabetes Mellitus (T2DM) is diagnosed using accepted biochemical criteria for diabetes.

The diagnosis is supported by:

  • Elevated fasting plasma glucose
  • Elevated HbA1c
  • Abnormal oral glucose tolerance test
  • Or markedly elevated random plasma glucose with classic symptoms

The clinical context helps distinguish Type 2 Diabetes Mellitus (T2DM) from Type 1 Diabetes Mellitus, monogenic diabetes, secondary diabetes, and other causes of hyperglycemia.

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Management

1. First-Line / Emergency Management

For stable patients:

  • Confirm diagnosis and assess cardiovascular and renal risk.
  • Begin lifestyle intervention.
  • Start glucose-lowering medication when indicated.

For severe hyperglycemia or hyperosmolar hyperglycemic state (HHS):

  • Urgent hospital management
  • Intravenous fluids
  • Electrolyte correction
  • Insulin when indicated
  • Identification and treatment of the precipitating cause
  • Close monitoring

2. Definitive Treatment

Management aims to achieve:

  • Individualized glycemic targets
  • Healthy body weight
  • Blood pressure control
  • Lipid control
  • Cardiovascular risk reduction
  • Prevention of microvascular complications

3. Medical Treatment

Metformin

  • Common first-line glucose-lowering medication.
  • Reduces hepatic glucose production.
  • Particularly useful when there are no contraindications.

Sodium-Glucose Cotransporter-2 (SGLT2) Inhibitors

Examples:

  • Empagliflozin
  • Dapagliflozin

Particularly useful in appropriate patients with:

  • Heart failure
  • Chronic kidney disease
  • Increased cardiovascular risk

Glucagon-Like Peptide-1 (GLP-1) Receptor Agonists

Examples:

  • Semaglutide
  • Dulaglutide
  • Liraglutide

Useful for:

  • Glycemic control
  • Weight reduction
  • Cardiovascular risk reduction in appropriate patients

Dual Glucose-Dependent Insulinotropic Polypeptide/GLP-1 Receptor Agonist

  • Tirzepatide

Provides potent glucose-lowering and weight-loss effects and may be appropriate for selected patients.

Sulfonylureas

Examples:

  • Gliclazide
  • Glimepiride

They increase insulin secretion but can cause:

  • Hypoglycemia
  • Weight gain

Dipeptidyl Peptidase-4 (DPP-4) Inhibitors

Examples:

  • Sitagliptin
  • Linagliptin

They provide modest glucose lowering and generally have a low risk of hypoglycemia when used without insulin or sulfonylureas.

Thiazolidinediones

  • Pioglitazone

Improves insulin sensitivity but may cause weight gain and fluid retention.

Insulin

May be required when:

  • Severe symptomatic hyperglycemia is present
  • There is marked catabolism or weight loss
  • Oral/non-insulin therapies are insufficient
  • Contraindications to other therapies exist
  • Acute hyperglycemic emergencies occur

Complications

-Acute Complications:

  • Hyperosmolar hyperglycemic state
  • Diabetic ketoacidosis
  • Hypoglycemia, particularly from insulin or insulin-secretagogue therapy
  • Severe dehydration

-Microvascular Complications:

  • Diabetic retinopathy
  • Diabetic nephropathy
  • Diabetic neuropathy

-Macrovascular Complications:

  • Coronary artery disease
  • Myocardial infarction
  • Stroke
  • Peripheral arterial disease

Other Complications:

  • Diabetic foot ulcers
  • Recurrent infections
  • Erectile dysfunction
  • Gastroparesis
  • Increased cardiovascular mortality

Prognosis

The prognosis varies according to the duration of diabetes, glycemic control, cardiovascular risk factors, kidney function, and development of complications.

Good control of:

  • Blood glucose
  • Blood pressure
  • Lipids
  • Body weight

can substantially reduce the risk of long-term complications.

Key Points / Clinical Pearls

  • Type 2 Diabetes Mellitus (T2DM) is characterized by insulin resistance and progressive beta-cell dysfunction.
  • It is the most common type of diabetes.
  • Major risk factors include obesity, physical inactivity, family history, and increasing age.
  • Many patients are asymptomatic for years.
  • Classic symptoms include polyuria, polydipsia, fatigue, and blurred vision.
  • Acanthosis nigricans is a clinical marker of insulin resistance.
  • Diabetes can be diagnosed using fasting glucose, HbA1c, oral glucose tolerance testing, or random glucose with classic symptoms.
  • HbA1c ≥6.5% is a diagnostic criterion when appropriately measured.
  • Lifestyle modification is an essential component of treatment.
  • Metformin is a common first-line medication when appropriate.
  • SGLT2 inhibitors and GLP-1 receptor agonists have important cardiovascular, renal, and/or weight-related benefits in selected patients.
  •  
  • American Diabetes Association Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1). Diabetes Care .
  • American Diabetes Association Professional Practice Committee. 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1). Diabetes Care .
  • American Diabetes Association Professional Practice Committee. 10. Cardiovascular Disease and Risk Management: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1). Diabetes Care .
  • Davies MJ, Aroda VR, Collins BS, et al. Management of Hyperglycemia in Type 2 Diabetes, 2022. A Consensus Report by the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care. 2022;45(11):2753-2786. Diabetes Care .
  • National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Type 2 Diabetes . National Institutes of Health.
  • World Health Organization. Diabetes . World Health Organization.