BACKGROUND Dysnatraemia is common in patients with heart failure and is associated with adverse outcomes. This association is independent of the underlying cause of heart failure and the level of left ventricular compromise. Hyponatraemia in heart failure is probably caused by neuroendocrine dysregulation of the renin–angiotensin–aldosterone system and the sympathetic nervous system, arterial underfilling with consecutive, baroceptor-mediated, Non-osmotic vasopressin secretion, and diuretic therapy. Hypernatraemia is more likely to occur in geriatric and intensive care patients. It is associated with inability to maintain an adequate volume balance (due to physical or mental impairment), parenteral nutrition and an impaired feeling of thirst. AIM To aim of this study was to determine the prevalence of dysnatraemia and its relationship to outcomes in hospitalised patients with heart failure in Jos University Teaching Hospital (JUTH). METHODOLOGY This was a multistage hospital-based study. The first stage was a cross-sectional study; the second stage, a cohort study. One hundred and twenty patients presenting to Jos University Teaching Hospital with heart failure were recruited consecutively over a 13-month period. Each participant was interviewed and examined by the investigator. Blood was drawn and sent to the Chemical Pathology Laboratory for analysis of serum sodium and other analytes. Twelve-lead electrocardiography and echocardiography were also carried out on all participants. Data were analysed using Epi Info version 7.2. RESULTS Out of the 120 participants in the study, 69 (57.5%) were male with a male-to-female ratio of 1.35:1. The age range of the study population was 18 – 92 years with a mean (± SD) age of 51.9 ± 16.6 years. Patients with hyponatraemia were older (55.1 ± 15.2 years), compared with those with normonatraemia and hypernatraemia (50.8 ± 17.2 years and 50.2 ± 16.8 years respectively) (P = 0.408). 29.2% of the study participants had hyponatraemia, 56.7% of them had normonatraemia, while 14.2% of them had hypernatraemia (P < 0.001). It then follows that the prevalence of dysnatraemia in the study population was 43.3%. Patients with dysnatraemia spent more days on admission compared with those with normonatraemia (13.0 ± 7.5 days versus 7.8 ± 4.8 days) (P < 0.001). Patients with dysnatraemia also had more complications than those with normonatraemia (65.4% versus 10.3%) (P < 0.001). A history of heart failure admission within the preceding 3 months was more common in patients with dysnatraemia compared with those with normonatraemia (40.4% versus 4.4%) (P < 0.001). Finally, there was a statistically significant difference in mortality between patients with dysnatraemia and patients with normonatraemia (21.2% versus 7.4%) (P = 0.030). CONCLUSION Dysnatraemia is a common finding in patients hospitalised with heart failure in Jos University Teaching Hospital. Patients with dysnatraemia have worse outcomes despite receiving the same heart failure evidence-based therapies with patients with normonatraemia. Definition of optimal sodium thresholds with regard to prognostic assessment, and the effect of various treatment strategies to normalise serum sodium in patients with heart failure should be subjects for further research.