Prevalence of elevated hemoglobin A1c among patients admitted to the hospital without a diagnosis of diabetes

J Clin Endocrinol Metab. 2008 Nov;93(11):4238-44. doi: 10.1210/jc.2008-1090. Epub 2008 Aug 12.


Context: One in four hospitalized patients has diagnosed diabetes. The prevalence of unrecognized, or undiagnosed, diabetes among hospitalized patients is not well established.

Objective: Our objective was to determine the prevalence of unrecognized probable diabetes in this patient population determined by elevated hemoglobin A1c (HbA1c) level.

Design: We conducted a prospective observational cohort trial with retrospective follow-up of patients with elevated HbA1c levels and no diagnosis of diabetes. HbA1c levels were obtained for all patients.

Setting: The study was conducted at an acute care general hospital.

Patients: Patients included 695 adult, nonobstetric patients admitted on 11 d in 2006.

Main outcome measures: Outcome measures included rate of unrecognized probable diabetes, defined as admission HbA1c of more than 6.1% and no diagnosis of diabetes or treatment with antidiabetic medications before or during their admission and rate of unrecognized diabetes 1 yr after discharge.

Results: Eighteen percent of hospitalized patients had elevated HbA1c levels without a diagnosis of diabetes. Random glucose levels poorly predicted elevated HbA1c levels (area under receiver operating characteristic curve, 0.60). Neither diagnosed diabetes nor HbA1c level was associated with length of stay or costs (P>0.1 for all comparisons). Only 15% of patients with elevated HbA1c levels who continued to receive care within the system studied had diabetes diagnosed in the year after the index admission.

Conclusions: Nearly one in five adult patients admitted to a large general hospital had unrecognized probable diabetes, based on elevated HbA1c levels. Random glucose levels during the hospital stay were poorly predictive of this condition. Few hospitalized patients with elevated HbA1c levels were diagnosed within the year after admission.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Aged
  • Blood Glucose / analysis
  • Boston
  • Diabetes Mellitus / blood
  • Diabetes Mellitus / diagnosis*
  • Diabetes Mellitus / epidemiology
  • Female
  • Glycated Hemoglobin* / metabolism
  • Hospital Bed Capacity, 500 and over / statistics & numerical data
  • Humans
  • Inpatients*
  • Male
  • Middle Aged
  • Prevalence
  • Reference Values


  • Blood Glucose
  • Glycated Hemoglobin A