Title: Injecting knowledge into language generation: a case study in auto-charting after-visit care instructions from medical dialogue. Abstract: Factual correctness is often the limiting factor in practical applications of natural language generation in high-stake domains such as healthcare. An essential requirement for maintaining factuality is the ability to deal with rare tokens. This paper focuses on rare tokens that appear in both the source and reference sequences, and which, when missed during generation, can hamper the factual correctness of the generated text. Starting from our fundamental premise that high-stake domains are also knowledge-rich, we show how to use knowledge to (a) identify what rare tokens that appear in both source and reference are important and (b) uplift their conditional probability. We introduce the ``utilization rate'' that encodes knowledge and serves as a regularizer by maximizing the marginal probability of selected tokens. We present a study in a knowledge-rich domain of healthcare, where we tackle the problem of generating after-visit care instructions based on patient-doctor dialogues. We verify that, in our dataset, specific medical concepts with high utilization rates are underestimated by conventionally trained sequence to sequence models. We observe that correcting this with our approach to knowledge injection reduces the uncertainty of the model and improves factuality and coherence without negatively impacting fluency. 