Our study shows patients with hyponatraemia upon admission to an inpatient rehabilitation unit have an increased rehabilitation LOS, yet they achieve comparable functional gain with ambulation and transfers. Figure 1 shows the mean admission and discharge FIM scores for hyponatraemic and eunatraemic patients, and the scores are fairly equivalent in each serum sodium group with no significant difference of the median functional change (2.0 points, P = 0.64). It is possible our patients with lower serum sodium levels had more subtle gait and attention impairments with increased fall risk, as seen in other studies, yet the abbreviated FIM scores used in this study were not able to fully demonstrate this. Subtle deficits not detectable by FIM score could be the cause of longer rehabilitation stays for hyponatraemic patients in order for them to attain a safe discharge functional status. Yet it remains difficult to conclude a direct causal relationship. As Fakhouri et al. (2012) in an editorial and many other authors have mentioned, is it the hyponatraemia causing these effects, or is it the severity of the original diagnoses (such as cancer) and their required inpatient-setting treatments causing these findings? This is an ongoing debate, and other studies are needed to evaluate this.