Objective: This article aims to address knowledge gaps and misconceptions among healthcare professionals regarding needle selection (specifically the length and gauge/size chosen) for intramuscular (IM) and subcutaneous (SC) injections. It investigates the impact of needle selection on injection efficacy and adverse effects, considering factors, such as, needle length, size, patient characteristics, and medication requirements. It also aims to evaluate current injection guidelines against research findings from the past two decades, identifying areas requiring revision or updating. Methods: The discussion paper employs a literature review, including an analysis of past research that employs imaging techniques, such as, CT and ultrasound to examine tissue depth in both IM and SC injection practices; the author's extensive experience across various clinical settings, including immunisation, primary care, and acute care settings. The author's roles as academic staff and a clinical facilitator allow for the identification of gaps between theoretical knowledge and practical implementation in injection practices. These insights contribute to a comprehensive understanding of the challenges faced by healthcare professionals. Results: The study reveals significant discrepancies in needle selection practices, with traditional methods often diverging from evidence-based recommendations. Challenges noted include reliance on needle hub colour coding for IM and SC injections and insufficient understanding regarding the rationale behind these injection methods. Another additional barrier is interpreting needle packaging information to identify the actual needle length for injection. Staff training and education is essential to improving accuracy and safety in injection practices. Further, patient characteristics, such as, weight, BMI, gender, and injection sites were found to impact needle selection, highlighting the need for tailored approaches. The article suggests that inconsistent and outdated guidelines from various agencies in injection practices and techniques often lack robust scientific rationale. Implications for research, policy, and practice: The findings and recommendations have significant implications for healthcare policies and guidelines. They highlight the need to incorporate research findings to update current guidelines, ensuring safe and effective injection practices across all clinical settings. An algorithmic flow chart could be developed to reflect the above concerns. What is already known about the topic? * Nursing textbooks often differ in IM and SC procedures, with some based on non-evidence-based recommendations. * Unsafe injections have severe consequences, including increased morbidity and mortality, along with substantial medical costs. * Complications like muscle fibrosis, abscesses, gangrene, and nerve injury may arise. Inappropriate injections can result in subtherapeutic absorption and reduced medication efficacy. What this paper adds: * This article highlights the overreliance on traditional practices in injection procedures and advocates for nurses to embrace evidence-based approaches in their injection techniques. * It also emphasises the importance of proper needle selection, including the correct identification of length and gauge/size (rather than relying solely on the needle colour hub for IM/SC injections), to ensure medication efficacy and patient safety. * This shift towards best practice is anticipated to enhance nursing proficiency in intramuscular and subcutaneous injections, ultimately leading to improved patient outcomes. [ABSTRACT FROM AUTHOR]