Yes, you should. It is necessary to avoid possible surprises like you might be rescued from the middle of the trekking due to altitude sickness or any other things. So, it is must. Do not forget to get your medical and travel insurance before visiting Nepal for trekking or tour. Such medical and travel insurance should cover proper altitude up to where you hike. This will benefit you at the time of evacuation by the helicopter if you are gripped by any kind of altitude sickness.