ObjectivesThis study aimed to investigate the effect of vitamin D supplementation therapy on disease activity and fatigue in rheumatoid arthritis (RA) patients.Material and methodsA prospective randomized clinical trial was conducted at rheumatology clinics in Tripoli Central Hospital, Libya. The eligible patients received disease-modifying antirheumatic drugs (DMARDs) and were divided into two groups: group A received 50,000 IU of vitamin D once a week; while group B received conventional DMARDs without vitamin D supplementation. The groups were monitored for 12 weeks.ResultsThe study included 68 RA patients, with the majority being female (75%). There were no significant differences in parameters such as age, sex, duration of illness, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), calcium, and vitamin D levels, as well as DAS28 (Disease Activity Score with 28-joint count) and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) levels between these two groups at baseline. After 12 weeks, group A showed a significant improvement in mean vitamin D levels and FACIT-F scores compared to group B. The increase in vitamin D levels in group A (24.21 ±4.81 nmol/l) was higher than that in group B (5.76 ±3.36 nmol/l). Furthermore, the FACIT-F score in group A was in the normal range (mean: 39.36 ±6.15), whereas group B still exhibited “abnormal” FACIT-F < 27.75 ±4.41. Correlation analysis indicated a positive correlation between FACIT-F and vitamin D levels, suggesting that higher vitamin D levels were associated with improved fatigue. Additionally, a weak inverse correlation was observed between DAS28 and vitamin D levels though the difference was not statistically significant (p > 0.05). Finally, the correlation between DAS28 and FACIT-F was positive (R = 0.557, p = 0.000).ConclusionsThe results of the recent study indicated that vitamin D3 (50,000 IU of cholecalciferol) supplementation had a positive impact in RA patients compared to conventional DMARDs drugs, as was clear from the significant FACIT-F.