Is it permissible for me to fast Ramadan while having only one kidney?

If a trustworthy, specialized doctor informs you that fasting will lead to illness, an increase in it, or a delay in your recovery, then you are permitted to break your fast, and you must make up the days if you become able to fast later. However, if the doctor tells you that fasting will not affect your health, then you are obligated to fast Ramadan, and you are not permitted to break your fast as long as you are able to do so.