Many people fast for religious reasons during Ramadan, Lent or at other times of the year. If you take daily medicine for high blood pressure, diabetes, heart disease or another long-term condition, the timing and dose of those medicines may need to change, and some people are advised against fasting. Speak with your doctor or pharmacist well before the fast begins, not on the first day. Many faith traditions allow exemptions for people whose health could be harmed, and a doctor can help you decide in a way that respects both.
People using insulin or certain diabetes tablets face a higher risk of dangerously low blood sugar when meals are skipped. Symptoms include shaking, sweating, confusion and a fast heartbeat, and a fast should be broken if they occur. Blood pressure tablets may need to be moved to the pre-dawn or evening meal, and fluid-removing medicines can cause dehydration. Never stop or halve a dose on your own. Drink plenty of water between sunset and dawn, avoid very salty or very sugary meals when breaking the fast, check your readings more often, and write them down so your doctor can adjust treatment.