Van Zyl et al’s study ^{Reference Szmukler, Richardson and Owen1} highlights the importance of increased awareness of venous thromboembolism (VTE) in mental health services for older people. However, it is also important to be aware of the risks of thromboprophylaxis within this setting. The authors claim that the incidence rates of VTE in old age mental health services were comparable with those in general hospitals. However, it does not follow from this that the same approaches for VTE screening and thromboprophylaxis used in general hospitals should be applied, particularly with respect to the risks of thrombocytopenia and bleeding from prophylactic low molecular weight heparin,² which may be exacerbated in mental health in-patient settings, where the average length of stay is likely to be longer than in an acute medical unit. In fact, recent meta-analyses have questioned whether such risks outweigh the potential benefits even within the general hospital setting.³ Further evidence should be sought before such VTE prevention strategies are widely implemented in mental healthcare settings, lest they lead to patient harm.