Aims: Nationally representative data on temporal changes in the prevalence of diagnosed diabetes, as well as undiagnosed diabetes and prediabetes, have been lacking in Germany as in most other European countries. We aimed to fill this gap using data from nationwide examination surveys of German adults.

Methods: The study population comprised 18–79-year-old participants from the German Health Interview and Examination Surveys in 1997–1999 (GNHIES98, n = 6655) and 2008–2011 (DEGS1, n = 7017). Participants were classified as having diagnosed diabetes based on self-reported physician-diagnosed diabetes or the use of anti-diabetes agents. Among those without diagnosed diabetes, HbA1c measures were used to define undiagnosed diabetes [≥ 48 mmol/mol (≥ 6.5%)] or prediabetes [39–47 mmol/mol (5.7–6.4%)].

Results: Although the age- and sex-standardized prevalence of total diabetes remained stable between 1997–1999 at 9.3% (95% CI 8.3–10.5%) and 2008–2011 at 9.2% (8.3–10.3%), the prevalence of diagnosed diabetes increased from 5.6% (4.9–6.3%) to 7.2% (6.5–8.0%), whereas the prevalence of undiagnosed diabetes decreased from 3.8% (3.1–4.6%) to 2.0% (1.5–2.7%), resulting in a decreased proportion of undiagnosed diabetes (40.9% vs. 21.7%). Over the same period, the prevalence of prediabetes decreased from 27.7% (25.6–29.8%) to 20.8% (18.2–23.7%). Observed temporal changes were not explained by changes in BMI, sport activity and educational level.

Conclusions: The two nationwide surveys indicate a shift from undiagnosed to diagnosed diabetes. However, the unchanged prevalence of total diabetes and the considerably high proportion of prediabetes strongly call for a continued and concerted effort in diabetes prevention among German adults.