Many cultures and religions across the world practice fasting, or the absence of caloric intake for a few hours to several weeks, at different times throughout the year. Islam, Judaism, Buddhism, Christianity, Hinduism, and Taoism religions most commonly use fasting for various reasons, but the overall purpose generally is to demonstrate sacrifice or spiritual cleansing.

Fasting may be harmful for patients undergoing cancer treatment who are dehydrated or malnourished, receiving nephrotoxic chemotherapy, at risk for tumor lysis syndrome, or need to take certain oral medications with food. Because of its implications on health, most religions and cultures consider fasting during a serious illness as self-harm and qualify illness as an exemption; however, some patients may still wish to fast or feel guilty if they do not. 

During multiple studies, less than half of patients undergoing treatment for cancer discussed their intent to observe religious fasting with their oncology team and only 20% talked with a religious leader about fasting during illness, sometimes citing certain religious texts that instruct about the private nature of fasting. Additionally, some of the patients who did engage their healthcare team or religious leader made attempts to fast despite being advised against it.

Nursing Considerations

Rather than waiting for patients to initiate questions, oncology nurses must identify patients’ cultural and religious beliefs, assess whether and how they practice fasting, and collaborate on solutions for those who wish to fast.

Clinical support for fasting during cancer treatment may include:

  • When possible, timing drugs between sunset and dawn if they need to be taken with a meal
  • Providing supplementary IV hydration if needed
  • Using a safe trial technique where a patient initiates fasting but is instructed on the signs and symptoms of when to stop fasting (e.g., dizziness, vomiting, diarrhea, poor intake overnight)
  • Recommending that patients ask their religious leader whether the fast may be observed later when they are no longer on treatment, which some religious texts encourage during illness
  • Encouraging patients of the Jewish religion to discuss the concept of a shiur with their religious leader, which may help them meet their desire to fast without increasing risk. The Jewish faith allows for consuming drink or food less than a shiur at specific time intervals. A shiur’s specific volume may vary slightly and should be confirmed with one’s rabbi.

Have you experienced a cultural clinical practice encounter or situation that would be helpful for other oncology nurses to understand? Email us about it at for consideration for a future article.

Acknowledgements: ONS thanks Rabbi Adrienne Rubin and Iman Yusaf Hasan for contributing to the development of this article.