As far as Islamic Shari`ah is concerned, an ill person whose condition requires taking medications during the day is allowed not to fast, as Almighty Allah says, (Whosoever of you is sick or on a journey, (let him or her fast the same) number of other days. Allah desires for you ease; He desires not hardship for you) (Al-Baqarah 2:185). Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states that:
Fasting, properly speaking, entails complete abstention from any intake of foods or drinks, including medicines or any other substances that goes to your belly or stomach. Therefore, if you take such medications, your fasting is undoubtedly rendered null and void.
If you are suffering from a medical condition that requires taking medications during the day, then you should skip fasting. You need to offer fidyah (compensation) that entails feeding a poor person for every single day of fast you missed. If, however, you hope to recover from this condition, then you need not offer fidyah; rather, you can simply make up for the days you have missed later whenever your condition improves and you are able to fast.