Determination of plasma osmolality is useful for determining proper administration of fluid therapy. In many reptilian species, the normal plasma osmolality is unknown. To prevent detrimental fluid shifts, knowledge of a patient's osmolality is imperative. The purpose of this study was to determine plasma osmolality in 11 healthy adult male bearded dragons (Pogona vitticeps) and to validate plasma osmolality equations that are used to calculate osmolality in other species. Venipuncture was performed via the ventral coccygeal vein, and plasma biochemical profiles were obtained from a point of care chemistry analyzer. Calculated plasma osmolality was determined using the following equations: 2 (Na K ), (2 [Na K ]) (Glu/18), (2 [Na K ]) (UA/16.8) (Glu/18), and 1.86 (Na ) Glu/18 UA/2.8 9. Plasma osmolality was measured in duplicate with a freezing-point depression osmometer, and the mean value was calculated for the two osmolality measurements. Measured and calculated plasma osmolalities, as well as the plasma biochemical analytes, were normally distributed. The mean measured plasma osmolality was 295.4 ± 9.35 mOsm/kg. There was poor agreement between the measured and calculated osmolalities. Because of these limitations, we modified the calculation [1.85 (Na K )] to account for expected differences in the primary cations and anions in reptile plasma. This newly proposed formula resulted in good agreement with the measured osmolality. Osmolality of the bearded dragons in this study was similar to that reported in dogs, cats, and other desert-dwelling saurian lizards. When administering fluids to a dehydrated or debilitated bearded dragon, caution is advised as calculated values are not an accurate measure of patient osmolality.