Exogenous sodium lactate has many advantages after traumatic brain injury, including intracranial pressure control and alternative energetic supply. It remains unclear, however, whether half-molar sodium lactate (HSL) is effectively incorporated in brain metabolism, which we can verify using the arteriovenous difference in lactate (AVD_lac ). Hence we compared the AVD_lac in patients with severe traumatic brain injury receiving an equiosmolar bolus of sodium lactate or mannitol for intracranial hypertension (IH) treatment. We included 23 patients: 14 received HSL for 25 IH episodes, and nine received mannitol for 19 episodes (total of 44 IH episodes). We observed that the median variation in AVD_lac was positive in the group that received HSL (Δ +0.1 [IQR -0.08-0.2] mmol/L), which suggests a net lactate uptake by the brain. On the other hand, it was negative in the group that received mannitol (Δ -0.0 [IQR -0.1 to 0.0] mmol/L), indicating a net lactate export. Finally, there were more positive AVD_lac values in the group that received HSL and more negative AVD_lac values in the group that received mannitol (Fisher exact p  = 0.04). Our study reports the first evidence of a positive AVD_lac , which corresponds to a net lactate uptake by the brain, in patients who received HSL for severe TBI. Our results constitute a bedside confirmation of the integration of lactate into the brain metabolism and pave the way for a wider dissemination of sodium lactate in the daily clinical care of patients with traumatic brain injury.