In the Ḥanafī madhhab, the obligation of ghusl is that water must flow over the entire outer body, including the skin. However, the jurists also clearly state that when there is a valid medical need that prevents water from reaching a part of the body, the ruling changes according to necessity.

The Ḥanafī jurists discuss cases such as bandages, plasters, medical dressings, and wounds. When removing such coverings would cause harm, delay healing, or create hardship, it is permitted to leave them in place and perform ghusl without removing them. In such cases, one washes what is accessible, and the ghusl remains valid. If wiping over the dressing is possible without harm, it is recommended; if even that is not possible, the obligation is waived due to necessity.

The principle underlying this ruling is that hardship and harm are lifted in the Sharīʿah. Allah says: “Allah intends for you ease and does not intend for you hardship.” (2:185). He also says: “He has not placed upon you in the religion any hardship.” (22:78).

Your glucose monitoring sensor is a medical device inserted under the skin and relied upon for proper diabetic management. Removing it would require discarding it and replacing it, and frequent removal could interfere with stable medical monitoring. Given that diabetes management is a serious and ongoing medical necessity, and that maintaining stable glucose control is essential to prevent harm, this situation falls under recognized medical need.

Therefore, according to Ḥanafī principles, your ghusl is valid while the sensor remains in place. You are not required to remove it. You should wash the entire body as normal, ensuring water flows over all accessible skin. If water can pass over the outer surface of the sensor without harm, you may allow water to flow over it, but you are not required to remove it to ensure water reaches the skin underneath.

There is no requirement for you to revert to finger-prick testing solely for the sake of ghusl validity. Your purification and prayers are valid, and you are not sinful for continuing to use a medically beneficial device.

You should not allow anxiety to overtake you in this matter. The Sharīʿah does not require a person to compromise their health in order to fulfill purification in a way that causes harm or serious inconvenience. The Prophet ﷺ said: “Indeed this religion is ease.” (Bukhari).