Removing blood from the body—whether by ḥijāmah (cupping), faṣd (venesection), or withdrawing blood to donate it for a patient—breaks the fast in every case.

Drawing only a small sample of blood, such as the amount taken for laboratory analysis, does not affect the fast. Likewise, bleeding that occurs involuntarily—through a nose-bleed, a cut, or the extraction of a tooth—does not invalidate the fast.

Among the nullifiers of the fast is vomiting: deliberately expelling the contents of the stomach—food or drink—through the mouth. Doing so invalidates the fast. If, however, one is overwhelmed by vomiting and it comes out without intention, the fast is not affected, for the Prophet ﷺ said: “Whoever is overcome by vomiting is not required to make up the day, but whoever induces vomiting intentionally must make it up.” The phrase “is overcome by vomiting” means it occurred against his will, whereas “induces vomiting” means he made himself vomit deliberately.

The fasting person should also avoid applying kohl or medicating the eyes with drops or the like during the day, in order to safeguard his fast.

He should likewise avoid exaggeration when rinsing the mouth or inhaling water into the nose during wuḍūʾ, for water might reach the stomach. The Prophet ﷺ said: “Be thorough in inhaling water into the nose—except when you are fasting.”