Red blood cell (RBC) transfusions are essential in health care. The quality of recommendations included in clinical practice guidelines (CPG), regarding this intervention, has not been systematically evaluated. This paper systematically assessed CPGs for RBC-transfusion, to appraise their methodological quality, to explore changes in quality over time, and to assess the consistency of the hemoglobin threshold (HT) recommendations. We searched for CPGs that included recommendations of RBC-transfusion in generic databases, compiler entities, registries, clearinghouses and guideline developers. Three reviewers extracted data on CPGs characteristics and HT recommendations, independently appraised the quality of the studies using AGREE II and resolved disagreements by consensus. We examined 16 CPGs. Mean scores (mean ± SD) were: scope and purpose (59.4% ± 19.8%), stakeholder involvement (43.2% ± 22.6%), rigor of development (50% ± 25%), clarity of presentation (74.4% ± 12.6%), applicability (19.4% ± 18.8%), and editorial independence (41% ± 30%). Seven CPGs recommended a restrictive strategy for RBC transfusion; four CPGs gave a guarded statement considering an HT of 7 g/dL, as safe to prescribe an RBC transfusion. Eight CPGs did not provide an HT stating that RBC transfusions should not be prescribed by HT alone. Only 3 out of the 16 evaluated CPGs were "recommended" by the independent evaluators. Four domains "stakeholder involvement," "rigor of development," applicability," and "editorial independence" had serious shortcomings. Recommendations about the use of an HT for RBC-transfusion were heterogeneous among guidelines. Greater efforts are needed to provide high-quality CPGs in the RBC-transfusion practice.