Background: Maintaining access to a broad range of old and new antibiotics is increasingly difficult due to supply, market, and demand issues. Next to immediate negative consequences for individual patients and healthcare systems, antibiotic unavailability can accelerate resistance development due to unmotivated use of suboptimal broad-spectrum antibiotics. Objectives: Although academics and policymakers agree that lack of access to antibiotics is a major public challenge, there are widely different situations of lack of access that are not always clearly identified. Therefore, this paper aims to clarify potential confusion by delving into four different types of lack of access, their specific causes, consequences, and potential solutions. Sources: The paper builds on a narrative review of academic and policy literature about lack of access to antibiotics and potential solutions to address it. Content: We discuss causes as well as economic and clinical consequences of four different types of antibiotic unavailability: short-term shortages, long-term shortages, deregistrations, and lack of registration. The discussion is supported by examples from Norway, Romania, and Ethiopia, three countries characterized by clearly different market sizes and ability to pay. Common causes for all types of lack access include unattractive markets, dependence on few suppliers and insufficient communication, whereas other causes are specific to one type (e.g. insufficient inventories cause short-term shortages or regulatory complexity hinders registration). Longer lack of access entails more serious clinical consequences and higher risk of resistance development, but may not correspondingly increase costs in the long-term if alternatives are identified. Implications: It is essential to understand the type of unavailability at hand because no single solution can address all types. For instance, stockpiling addresses short-term shortages, but not long-term ones or deregistrations. However, supply chain transparency and pooled procurement are remedies that support other solutions and can cope with several types of lack of access. Enrico Baraldi, Clin Microbiol Infect 2025;31:333 (c) 2024 The Author(s). Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).