Why was this study done?: Health care needs of autistic adults are often unmet. This may contribute to poorer health outcomes in autistic compared with nonautistic adults. Autistic differences may not be obvious in this group because of behavioral compensation strategies. Health care providers may underestimate the support needs of autistic adults, leading to decreased quality of care. By analyzing autistic adults' own experiences, we may better understand barriers to effective health care. What was the purpose of this study?: We aimed at identifying patterns of sensory and communicative experiences that autistic adults find problematic in health care settings. What did the researchers do?: In an online questionnaire, we asked autistic and nonautistic adults how they experienced various medical settings. We focused on specific sensory inputs, such as light levels and background sounds, in waiting rooms and other medical contexts. We also asked questions about communication between patients and providers. Finally, we did a qualitative analysis on free-text responses about sensory environments for both groups, and about communication for the autistic group. What were the results of the study?: Ninety-eight people (62 autistic) participated. Most of the cohort was female or gender-diverse, middle-age, and well educated. Autistic participants identified auditory inputs as one of the greatest stressors in medical settings. They discussed the impact of light levels and other people's presence on their energy levels and ability to communicate. Health care providers often misunderstood their autistic patients, leading to a failure in transferring medical information. Participants described how providers underestimated their needs, even when they were aware of the autism diagnosis. Participants wanted to get information delivered at a slower pace and with a greater amount of detail, to be better able to process medical or procedural information. What do these findings add to what was already known?: The study contributes with information on specific sensory challenges and suggests that auditory noise is particularly problematic for autistic people. On the topic of communication, the findings point to a "double empathy" problem, whereby the provider's own limitations contribute significantly to communication barriers. This was apparent in accounts of nonverbal communication, where the provider's expectations of neurotypical body language caused misunderstandings that were difficult to overcome. What are the potential weaknesses in the study?: The sample was small and comprised an ethnically narrow demographic group. Thus, the results are not generalizable to other autistic populations, such as minimally verbal adults. We also did not measure health status beyond diagnosed conditions. How will these findings help autistic adults now or in the future?: The consequences of sensory and communicative barriers may go entirely unnoticed when autistic differences are not visible. Unsuccessful interactions with the health care system may have enormous effects on the health and quality of life of autistic people. Therefore, educators and providers may use the insightful information provided by autistic participants in this study to inform decisions on staff training or design of sensory environments.