If you are travelling for treatment and looking at a week of hotel nights, this is the first thing worth resolving, because the answer changes what you should book. The short version is that your medical plan probably will not pay, but there are four or five specific places the money can come from instead, and most people never check any of them.
Health plans pay for medical services. A hotel room is not one, however necessary it is to receiving the care. That is the whole of the reasoning, and it is why you will not usually find lodging in a summary of benefits at all rather than finding it listed and excluded.
It is worth being precise about the question you ask, though. "Do you cover hotels" gets a fast no from almost any call centre. "Does this plan include a travel or lodging benefit for care received outside my area" is a different question, and it is the one that occasionally gets a yes.
Each of these is real, each covers a different group of people, and they are easy to miss because none of them lives in the part of the plan documents anybody reads.
This one catches people out, because it is not really about coverage. Even where your plan pays nothing, lodging while away from home for medical care can be a qualified medical expense, which means you may be able to pay for it with pre-tax HSA or FSA money.
The limits are specific and low. The care has to be received at a licensed facility, the stay cannot be lavish, there can be no significant element of recreation in the trip, and the amount is capped per night per person. It is not a lot of money, but it is real, and it applies to a caregiver travelling with you as well.
The person on the other end of the insurance line is answering the question you asked, so the phrasing matters more than it should. Three calls usually settle it.
Whatever the answer turns out to be, treatment dates move. Clinics reschedule, procedures get delayed, and a course of treatment that was five days becomes seven.
The single most useful thing you can do while you are still working out who pays is to make sure whatever you book is cancellable, and to know the deadline. A cheaper non-refundable rate stops being cheaper the first time a date moves.
Usually not for a commercial medical plan. A letter of medical necessity matters for HSA or FSA reimbursement, and for some employer travel benefits, but it does not generally turn lodging into a covered medical service.
Original Medicare does not cover lodging as a benefit. Some Medicare Advantage plans include supplemental transportation or travel benefits, so it is worth checking your specific plan rather than assuming.
The lodging limit is set per night per person and is deliberately modest, and a companion travelling with you may be counted separately. The conditions matter as much as the number: the care has to be at a licensed facility and the trip cannot have a significant recreational element.
Ask the study coordinator first. Trial sponsors commonly cover travel and lodging for participants, and that support is arranged through the study rather than through your insurance.