Metabolic syndrome, also known as syndrome X or insulin resistance syndrome, refers to the co-occurrence of metabolic risk factors for both type 2 diabetes mellitus and coronary vascular disease, including abdominal obesity, hyperglycemia, dyslipidemia, and hypertension. Prevalence continues to increase worldwide, especially in African-American and Mexican-American populations. Risk factors for development include an elevated body mass index (BMI), especially abdominal obesity, increasing age, African-American or Mexican-American descent, postmenopausal status, smoking, a high-carbohydrate diet, physical inactivity, clozapine use, and low household income.

The US National Cholesterol Education Program Adult Treatment Panel (ATP) III definition of metabolic syndrome requires patients to have any 3 of the following 5 traits:

1. Abdominal obesity – Waist circumference ≥ 102 cm (40 inches) for men and ≥ 88 cm (35 inches) for women.
2. Serum triglycerides ≥ 150 mg/dL or drug treatment for elevated triglycerides.
3. High-density lipoprotein (HDL) < 40 mg/dL in men and < 50 mg/dL in women or drug treatment for low HDL cholesterol.
4. Blood pressure ≥ 130/85 mm Hg or drug treatment for elevated blood pressure.
5. Fasting plasma glucose ≥ 100 mg/dL (5.6 mmol/L) or drug treatment for elevated blood glucose.