Type 2 diabetes mellitus

Type 2 diabetes accounts for approximately 90% of all cases of diabetes. Insulin resistance is the cardinal pathogenic factor and patients are therefore initially hyper insulinaemic although eventually beta cell failure intervenes. Diagnosis is often made on clinical grounds but can be confirmed by measuring C-peptide and/or insulin levels. Management is by a combination of lifestyle changes, oral hypoglycamics and eventually insulin therapy becomes unavoidable in the overwhelming majority of cases.

Has the patient been drinking more water and passing more urine than usual?

Polyuria and polydipsia are the cardinal symptoms of diabetes and occur when the blood glucose level exceeds the renal threshold for glucose excretion - usually approximately 10 mmol/L.

Has the patient noticed a change in eye sight - particularly an inability to focus?

Variable difficulty with focusing - particularly if present for only a short period and fluctuating - is due to osmotically driven swelling of the lens and varies as the degree of hyperglcaemia varies.

Has the patient lost weight without trying?

Weight loss is a relatively unusual feature in the presentation of T2DM.

Significant weight loss in association with a new diagnosis of diabetes, especially in a patient who is already lean, should prompt the physician to consider a diagnosis of type 1 diabetes or other causes of diabetes, such as post-pancreatitis diabetes.

Has the patient developed generalised itch without rash or any other obvious cause? 

Pruritis is a classical symptom of hyperglycaemia although not seen as commonly as the osmotic symptoms.

Has the patient developed genital thrush?

Hyperglycaemia impairs neutrophil and macrophage function at the same time as producing a more favourable environment for micro-organisms to grow.

Infections generally are therefore more common in the hyperglycaemic patient and genital candidiasis is a particularly prevalent example.

Has the patient any other relatives with diabetes?

T2DM often runs quite strongly in families. 

A complete absence of family history of diabetes should at least prompt consideration of alternative diagnoses which may include LADA.

A family history will also help to detect rare monogenic causes of diabetes such as MODY (maturity onset diabetes of youth), mitochondrial diabetes or APECED (auto-immune polyendocrinopathy, candidiasis and ectodermal dystrophy) that might otherwise be missed.

Is the patient taking any other medicines such as steroids?

Steroid induced diabetes is really a variant of T2DM and can be treated with oral hypoglycaemics, although they have increased chance of requiring insulin early on after the diagnosis.

Does the patient have a past medical history of pancreatitis, malabsorption, pancreatectomy or cystic fibrosis?

Any of these conditions may predispose to loss of beta cell mass. If so, this would indicate a cause of diabetes other than T2DM.

Is the patient completely asymptomatic?

Patients with diabetes, and especially T2DM, are commonly picked up on screening bloods carried out for some other indication.

In the absence of symptoms, two fasting blood glucose tests higher than 7 mmol/L, or two random levels higher than 11.1 mmol/L, are required to confirm the diagnosis (these levels assume that the patient does not have an inter-current illness, otherwise the diagnosis is, strictly speaking, of 'stress hyperglycaemia').

Alternatively a formal 75 g oral glucose tolerance test can be conducted, but in practice is not often necessary and, where the diagnosis is obvious, should not be performed.

Although there is much interest in using HbA1c as a diagnostic test, this has not yet been formally adopted by the WHO and we therefore advise against its use for this purpose.

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