To investigate the relationship between admission glycaemic status and inpatient mortality in patients with and without pre-existing diabetes.

Prospective observational cohort study.

A general medical ward in an Australian tertiary referral hospital.

903 patients admitted to the general medical ward between February 2003 and July 2004.

Inpatient death.

The overall inpatient mortality was 5.4% (n = 49). In the total cohort, age > 75 years and admission fasting plasma glucose (FPG) levels ≥ 5.6 mmol/L were independent predictors of mortality. For patients without a known history of diabetes, each 1 mmol/L rise in admission FPG was associated with a 33% increase in mortality. In these patients, elevated (> 6.0%) and normal glycated haemoglobin (HbA1c) levels were associated with mortalities of 11.3% and 4.4%, respectively (odds ratio, 2.47; 95% CI, 1.16–5.26). In contrast, in patients with known diabetes, there was no association between admission FPG levels, HbA1c and mortality. Length of stay was not independently associated with FPG, HbA1c, or diabetes status.

In patients without known diabetes, the risk of death was increased for admission FPG levels ≥ 5.6 mmol/L. However, pre-existing abnormal glucose metabolism, reflected by elevated HbA1c levels, appeared a more important predictor of inpatient mortality than glucose levels in patients without known diabetes.