5,360 patients were included. 51.7% were male, and the median age was 67 years (IQR 50-79). 77.2% had low lactate (0-1.9 mmol/L), 16.2% intermediate lactate (2-3.9 mmol/L), and 6.6% high lactate (≥4 mmol/L). 7-day mortality was 2.9% (95% CI 2.4-3.5%) for patients with low lactate, 7.8% (95% CI 6.1-9.8%) for patients with intermediate lactate, and 23.9% (95% CI 19.6-28.8%) for patients with high lactate. There was a significant trend for increasing 7-day mortality with increasing lactate among patients with a discharge diagnosis categorized as infectious (N = 1,133), cardiologic (N = 357), respiratory (N = 633), hypovolemic (N = 205), or gastrointestinal (N = 222). Whereas patients with neurologic- (N = 391) or nephrologic/hepatologic discharge diagnoses (N = 94) showed no trend.