Exceptions to particular fasting rules: Orthodox Christians must always fast in ways that are not a detriment to one’s health (to do things that harm the body goes contrary to the faith). Particular fasting disciplines are relaxed, when necessary, when one is travelling or ill. Also, when receiving the hospitality of others (if someone invites you to dinner, for example, go and receive with thanksgiving what is set before you).
For those who live in households where not everyone is Orthodox, for example, modifications will need to be made for everyone to be able to eat as a family. If you have not already, consult the priest and maybe make a good fasting plan that works for you. For those who have special health needs, for example diabetes, modifications need made to fasting rules. In such a case, fasting from all foods that are unhealthy may be your form of fast. Likewise, those who take medications that require a certain pattern of eating should do so as needed.
In general, the words of St. Isaac of Syria are pertinent for exceptions, where he states: “If you cannot fast for two days in a row completely, at least fast until evening. And if you cannot fast until evening, then at least keep yourself from eating too much.” (Homily 51).