Background Blood lactate is a marker of patient illness severity. Capillary lactate (CAP-LACT) measurement can potentially improve patient screening; however, it has poor evidence of clinical utility.

Aim We aimed to investigate agreement between CAP-LACT and peripheral venous lactate (PV-LACT).

Methods We performed a prospective observational pilot study of 99 patients requiring lactate measurement. Paired CAP-LACT and PV-LACT was recorded. Agreement was determined by Bland-Altman analysis.

Results Bias was 0.2 mmol/L, with 95% limits of agreement from −1.9 to 2.3.

Conclusions CAP-LACT has poor agreement with PV-LACT. Further research is needed to improve its potential clinical utility.