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.

FBC

Baseline haematological and biochemical investigations are mandatory in all newly presenting cases of diabetes.

Urea and electrolytes

Assessment of urea and creatinine is essential to gauge renal function as metformin therapy is contra-indicated with a serum Cr of >150 micromol/L or an eGFR of <30 ml/min.

Liver function tests

Baseline haematological and biochemical investigations are mandatory in all newly presenting cases of diabetes.

Furthermore, abnormal LFTs secondary to non alcoholic fatty liver disease is increasingly common.

Fasting or random glucose

In most symptomatic cases the degree of hyperglycaemia will be such that there is no doubt about the diagnosis.

However, in borderline cases WHO criteria for diagnosis should be applied. These are that a fasting plasma glucose >7 mmol/L, or a random plasma glucose >11.1 mmol/L on one occasion in symptomatic patients or two occasions in asymptomatic patients, indicates a diagnosis of diabetes mellitus.

If these criteria are not met it may be necessary to perform a 75 g oral glucose tolerance test. The same biochemical cut offs are used for the fasting and two hour values.

Fasting lipid profile

Hypercholesterolaemia and hypertriglycerideamia are important cardiovascular risk factors in patients with T2DM and should be measured at baseline as they are likely to require specific treatment with a statin and/or a fibrate.

ECG

Not normally necessary but may be performed if there is suspicion of pre-exisiting ischaemic heart disease.

HbA1c

This is often performed at diagnosis but in actual fact contributes very little at this stage as it will almost invariably be elevated.

The WHO have recenly recommended that HbA1c may be used as diagnostic test for diabetes with a cut off of 6.5% (48 mmol/mol) but this practice has not yet been formally adopted in the UK.

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