Classification of Diabetes Mellitus

Type 1:
Characterised by an absolute lack of insulin as a result of pancreatic islet cell destruction. It often has a sudden onset and patients with type 1 diabetes need insulin treatment for survival in order to avert the development of diabetic ketoacidosis. Usually develops before the age of 35 years but can be diagnosed at any age.

Type 2:
Characterized by relative resistance to insulin in addition to pancreatic beta cell dysfunction. It has a slower and more insidious onset and tends to occur in middle-aged adults and the elderly. There have, however, been increasing reports of Type 2 diabetes developing in teenagers and young adults, mainly in association with obesity. Patients with type 2 diabetes mellitus are not prone to diabetic ketoacidosis.

Secondary diabetes:
Diabetes secondary to pancreatic disease, Cushing's syndrome and other endocrinopathies, or due to drugs such as glucocorticoids

Patients with the following symptoms:

• Thirst, polyuria and weight loss
• Recurrent skin infections
• Neuropathic symptoms such as pain, numbness and paraesthesia
• Blurred vision
• Lassitude or lethargy
• Recurrent thrush

Patients with:

• Hypertension
• Ischaemic heart disease
• Peripheral vascular disease
• Cerebrovascular disease
• Obesity
• South Asians and African Caribbeans
• A family history of diabetes or cardiovascular disease
• A history of gestational diabetes or polycystic ovary syndrome

1. Diabetes symptoms (polyuria, polydipsia and unexplained weight loss) plus
   Random venous plasma glucose 11.1 mmol/l or higher OR
   Fasting plasma glucose 7.0 mmol/l or higher OR
   2 hour plasma glucose concentration 11.1 mmol/l or more, 2 hours after 75g anhydrous glucose in an oral glucose tolerance test (OGTT - link)
2. If asymptomatic
   2 samples on separate days, either random or fasting, or after an OGTT are needed to confirm the diagnosis. Exceptions - ketoacidosis, children

Most cases can be confirmed with random/ fasting glucose measurement and an OGTT is infrequently necessary.

Other diagnostic criteria

1. Impaired Fasting glucose (IFG)
   Fasting glucose 6.1-6.9 mmol/l
2. Impaired glucose tolerance (IGT)
   Fasting glucose <7mmol/l
   2 hour glucose 7.8-11 mmol/l