Objective Population data on dysglycemia are scarce in West Africa. This study aimed to determine the pattern of dysglycemia in Calabar city in South East Nigeria.

Design This was a cross-sectional observational study.

Methods 1134 adults in Calabar were recruited. A multistage sampling method randomly selected 4 out of 22 wards, and 50 households from each ward. All adults within each household were recruited and an oral glucose tolerance test was performed. Dysglycemia was defined as any form of glucose intolerance, including: impaired fasting glucose (blood glucose level 110–125 mg/dL), impaired glucose tolerance (blood glucose level =140 mg/dL 2 h after consuming 75 g of glucose), or diabetes mellitus (DM), as defined by fasting glucose level =126 mg/dL, or a blood glucose level =200 mg/dL, 2 h after a 75 g glucose load.

Results Mean values of fasting plasma glucose were 95 mg/dL (95% CI 92.1 to 97.5) for men and 96 mg/dL (95% CI 93.2 to 98.6) for women. The overall prevalence of dysglycemia was 24%. The prevalence of impaired fasting glucose was 9%, the prevalence of impaired glucose tolerance 20%, and the prevalence of undiagnosed DM 7%. All values were a few percentage points higher for men than women.

Conclusions The prevalence of undiagnosed DM among residents of Calabar is similar to studies elsewhere in Nigeria but much higher than the previous national prevalence survey, with close to a quarter of the adults having dysglycemia and 7% having undiagnosed DM. This is a serious public health problem requiring a programme of mass education and case identification and management in all health facilities.