Objectives The aim of this observational study was to explore dabigatran concentrations in elderly and very elderly patients in a real-life population. Patients aged >75 years receiving dabigatran have a significantly higher risk of gastrointestinal bleeding compared withthose receiving warfarin. High trough concentrations have an important impact on this bleeding risk.

Methods We measured dabigatran trough concentrations in 75 patients with atrial fibrillation, divided into age categories <75, ≥75 to 84 and ≥85 years. The most important exclusion criteria were use of interacting medication and severe renal failure. We analysed absolute trough concentrations and concentrations normalised for dose.

Results Trough concentrations were considerably higher in the highest age category. Dose-normalised medians were 0.66, 0.83 and 1.20 ng/mL/mg in the <75, ≥75–84 and ≥85 age groups, respectively (p=0.004).

Conclusion Clinicians should be aware of higher dabigatran concentrations in elderly patients despite dose reduction.