Abstract Previously, glucose concentration has been presumed to be similar in seroma, lymph, and plasma. However, there are few studies actually measuring glucose concentration in seroma. The aim of this pilot study was to determine if the glucose concentration in seroma is similar to that in plasma, as it has previously been presumed. Biochemical analysis of seroma was performed on 11 patients that had undergone plastic surgery. Fluid was taken from the drains between postoperative day 3 and 6. The median glucose concentration was 3.09 millimolar (mM) (range 2.25-3.89 mM). Glucose concentration in seroma does not seem to be similar to that of plasma and lymph that has previously been presumed. The result of this pilot study warrants further investigation to determine the span of normal glucose concentration, its development over time, its relation to plasma glucose concentration, and how it is affected by infection.