When enough is enough: Understanding saturation in qualitative research

Despite its widespread use in qualitative research, saturation is often improperly stated or loosely used in the methods section and cited as a methodological checkbox to persuade editors and peer reviewers that research methodology is robust. This narrative review sheds light on this multifaceted concept, tracing its origin in grounded theory to its current, diluted applications across qualitative methodologies. Four conceptually distinct forms of saturation are synthesized: theoretical saturation, where researchers can no longer develop category properties due to lack of new data; inductive thematic saturation, where more data yield no new codes or themes; a priori thematic saturation, where sufficient examples exist for predefined categories in an existing theory; and data saturation, where new information merely restates what has already been heard, without offering new perspectives. Empirical evidence indicates saturation is often achieved within 9 to 17 In-Depth Interviews and 4 to 8 Focus Group Discussions, yet these are estimates, not fixed rules, and parameters such as study goals, population, and sampling strategy influence when saturation is reached. Most qualitative researchers stop data collection not because saturation is truly achieved but because of budgetary and time constraints. Saturation should not be regarded as a rigid universal rule but must align with the goals of the research, guiding, not dictating, qualitative inquiry. This review emphasizes defining saturation properly, aligning it with analytical and epistemological methods, and reporting it separately in the protocol and publication for transparency rather than retrofitting the label to satisfy editors and peer reviewers.