Objective: To compare the efficacy and safety of intravenous and oral iron supplementation in adult patients with iron deficiency anemia (IDA) and chronic kidney disease (CKD) who are not on dialysis (NDD-CKD). Methods:A literature search was performed for English-published studies from inception till November 1, 2022. The search included MEDLINE/PubMed, Cochrane Library, Academic Search Complete (EBSCOhost) and Web of Science using the terms ("Chronic renal insufficiency") AND ("Iron-deficiency anemia") and ("Iron Compounds"). Results: Twelve studies were included.Intravenous iron showed significantly higher final levels of haemoglobin (MD: 0.39, 95% CI: 0.29 to 0.49, p<0.001), ferritin (MD: 196.81, 95% CI: 113.57 to 280.05, p<0.001) and transferrin (MD: 4.02, 95% CI: 1.87 to 6.17, p<0.001). The rate of overall adverse effects was higher in the oral group (RR: 0.77, 95% CI: 0.59 to 1.00, p=0.05). However, intravenous iron was significantly associated with a higher risk of allergic reaction/hypotension (RR: 3.87, 95% CI: 2.00 to 7.51, p<0.001) and infection (RR: 1.72, 95% CI: 1.11 to 2.66, p=0.01). Conclusions:The evidence suggests that intravenous iron supplementation may be superior to oral iron in improving the haemoglobin, ferritin and transferrin levels in NDD-CKD patients. However, intravenous iron increases the risk of serious adverse effects. Because of the limitations of the studies included in this review, it is recommended to carry out large, randomized trials to assess