Is religion considered deficient due to the inability to fast because of diabetes?

What you feel regarding the belief in a deficiency in religiosity and deprivation from good is from the whispers of Satan. Strive against yourself to rid yourself of it, and be patient, seek reward from Allah, and be content. For if a servant is patient, seeks reward from Allah, and is content with Allah's decree and destiny, Allah will raise him to the ranks of His close servants.