– Q. My naturopathic doctor said that I should not fast (in days like 17 Tamuz) so I was thinking to wake up early to eat breakfast and then eat lunch later in the day. However, I forgot it was a fast day and scheduled an appointment to donate blood. 

Although this is a nice thing to do, I  am doing it for medical purposes as I have too much iron in my blood. They require drinking 500 ml and eating a salty snack before donating. Can I still do it or do I need to change the day?

A. Poskim usually are lenient on cases that seem as serious as what you describe and no fasting is necessary. However, if you can without any harm fast a few hours at the early beginning, it is also correct.

A well trained and expert MD that is familiar also with these Shailos should be constantly consulted for every change you may make.
Horav Shlomo Miller Shlit’a opinion is similar.

Rabbi A. Bartfeld as revised by Horav Yaakov Hirschman, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.