There are numerous synonyms for the phrase "in bad health." Some of these include "ill," "unwell," "sickly," "ailing," "weak," "feeble," "debilitated," "infirmed," "indisposed," "under the weather," "ailing," "afflicted," "infirm," "sickly," "weakly," and "challenged." These words all convey a sense of physical or mental unwellness, indicating that an individual may require medical attention or care. They can be used interchangeably but have varying degrees of severity. While some may indicate minor discomfort, others may suggest a more serious condition or long-term ailment. Overall, it is important to choose the most appropriate synonym based on context and degree of severity.