As a U.S. foreign student (on an F-1 or M-1 visa), your right to remain in the U.S. depends on maintaining your student immigration status throughout your studies. That means, for example, going to school as expected, pursuing a full course of study, and getting approval from your designated school official (DSO) before pursuing any changes in your overall plan.
But what happens if you become too sick to go to class full-time or otherwise comply with the terms of your F-1 student visa in the United States?
A “full course of study” means that you cannot be going to school on a part-time basis. Your study must “lead to the attainment of a specific educational or professional objective.” This can be a degree such as a Bachelor’s, Master’s, Ph.D., or other certification.
But perhaps you don't need to put in as many school hours as you think. The following types of study are acceptable:
You will be allowed some breaks in your study regimen. These are typically winter and summer breaks. You are not allowed a break for personally scheduled vacations that disrupt your studies during the academic term and prevent you from completing your coursework.
If you still can't keep up with the required study hours, talk to your DSO, who can grant exceptions, including based on illness. Even if you didn't talk to your DSO in advance, and basically dropped out of school for a while, it's still worth getting in touch. Reinstating your student status may still be possible.
As soon as you are fully recovered, you are expected to resume a full-time course load.
If your illness prevents you from completing your studies by the date on your I-20, you will need to apply for an extension of time. The procedure for this involves filling out USCIS Form I-539 and, if and when you travel overseas, renewing your entry visa.