Rheumatoid arthritis (RA) is a complex inflammatory disease that modifies body composition. Although body mass index (BMI) is one of the clinical nutrition tools widely used to assess indirectly nutritional status, it is not able to identify these body alterations. Bioelectrical Vector Analysis (BIVA) is an alternative method to assess hydration and body cell mass of patients with wasting conditions. To investigate the differences in nutrition status according to BMI groups (normal, overweight and obesity) and BIVA classification (cachectic and non-cachectic) in women with RA. Women with confirmed diagnosis of RA were included from January 2015 to June 2016. Whole-body bioelectrical impedance was measured using a tetrapolar and mono-frequency equipment. Patients were classified according to BMI as: low body weight (n = 6, 2.7%), normal (n = 59, 26.3%), overweight (n = 88, 39.3%) and obese (n = 71, 31.7%), and each group was divided into BIVA groups (cachectic 51.8% and non-cachectic 48.2%). A total of 224 RA patients were included, with mean age 52.7 years and median disease duration of 12 years. Significant differences were found in weight, arm circumference, waist, hip, resistance/height, reactance/height and erythrocyte sedimentation rate among all BMI groups. However, serum albumin levels were significantly different between cachectic and non-cachectic patients independently of BMI. In all BMI categories, cachectic groups had lower reactance and phase angle than non-cachectic subjects. RA patients with normal or even high BMI have a significantly lower muscle component. Evaluation of body composition with BIVA in RA patients could be an option for cachexia detection.