is somewhat weak and unhealthy, then he/she may feel uncomfortable ---- Not necessarily due to X-ray per se, maybe due to something else (e.g., noise, even just mental stress: 太紧张)
not noramlly for any plain plate X-ray tests, eg. chest/abdominal x-ray; but certain people do experience nausea and vomiting when contrast is used for the procedure. The adverse effects usually does not last long and subside within hours.