A fluid characteristic indicator for measuring and indicating a characteristic of body fluid from a medical or veterinary patient has a tubular housing with suction and fluid inlet ports at opposite ends and a fluid characteristic indicating element disposed within. A diffuser supports the indicating element and has at least one fluid channel to direct fluid toward the indicating element. The fluid channel may be formed as a spiral or helix, or as a plurality of longitudinal fluid channels. The housing and the diffuser may have additional structures forming channels that cooperatively direct fluid toward the indicating element. The diffuser may occupy nearly all the interior volume of the housing. Control of the fluid flow may make exposure and saturation of the indicator more accurate, avoid spurious indications due to the color of the fluid itself, and reduce the amount of fluid sample needed to obtain an indication or measurement.
