Rheumatoid Arthritis (RA) is a chronic autoimmune disease that primarily affects the joints. In RA, the body’s immune system mistakenly attacks its own tissues, especially the synovial membrane causing inflammation, pain, swelling, and stiffness. This study was aimed at determining changes in some haematological markers and renal profile in rheumatoid arthritis patients attending Imo State Specialist Hospital Umuguma, Owerri, Imo State. A cross-sectional study was carried out from the month of June to September, 2023, and all eligible subjects who gave a written informed consent and completed the questionnaire enrolled in the study. The study population consisted of 50 rheumatoid arthritis and an equivalent number of age-matched healthy subjects (50), who served as the controls. The procedure was carried out at the Specialist Hospital, Umuguma, Owerri. Ten millilitres of venous blood sample was collected at the ante-cubital vein aseptically, 5ml was dispensed into ethylenediaminetetraacetic acid (EDTA) containers for the estimation of haematological parameters, while the remaining 5mls was dispensed into plain containers for the determination of biochemical parameters. The samples in the containers were properly labeled with the subject’s name, sample number and date of collection. The blood dispensed into the EDTA containers was stored in a refrigerator at 40C while the serum was stored in a freezer at -200C prior to use. Haematological parameters and renal profile test were determined using standard laboratory procedure. The results of the tests were analyzed using SPSS version 21. The mean values of haemoglobin (9.84±1.32) g/dl and PCV (30.97±2.43) % were significantly lower in rheumatoid arthritis patients when compared to controls (12.48±1.57) g /dl and (33.20±4.57) %, while platelets (33844.00±102083) cells/ul were significantly higher in rheumatoid arthritis patients when compared to controls (234180.00±132329.01). There was no significant difference in the mean value of creatinine (1.35±1.98) mg/dl, in rheumatoid arthritis patients when compared to controls (1.34±1.86) mg/dl. The mean values of urea (37.56±20.88) mg/dl, sodium (151.02±44.78) mmol/l and potassium (4.94±2.08) mmol/l were significantly raised in rheumatoid arthritis when compared to controls (26.27±15.16) mg/dl, (132.27±5.98) mmol/l and (4.76±1.19) mmol/l (p=0.012, p=0.001, p=0.026, p=0.010. There was a non-significant positive correlation of PCV with urea, creatinine, sodium and potassium in rheumatoid arthritis patients (r=0.04, p=0.767; r=0.10, p=0.474; r=0.01, p=0.975 and r=0.03, p=0.834). Early detection and management of anemia, thrombocytosis, and renal dysfunction are essential for improving patient outcomes and quality of life.