Lorazepam is a strong sedative for intensive care patients and a commonly used method of administering it to the patient is by infusion of a freshly prepared lorazepam solution. During lorazepam infusion often unwanted lorazepam crystallization occurs, resulting in line obstruction and reduced lorazepam concentrations. With the aid of solubility measurements a solid–liquid phase diagram for lorazepam in mixtures of a commercially available lorazepam solution and an aqueous glucose solution was determined. This confirmed that the glucose solution acts as an anti-solvent, greatly reducing the lorazepam solubility in the infusion solution. Three approaches are proposed to obtain stable lorazepam solutions upon mixing both solutions and thus to prevent crystallization during infusion: (1) using a high lorazepam concentration, and thus a lower glucose solution volume fraction, in the mixed solution; (2) using an elevated temperature during solution preparation and administration; (3) reducing the lorazepam concentration in the commercial lorazepam solution.