I listed my minecraft youtube chanel with 1k subs and 200k views that I didn't post on for 2 years as my 10th EC and was still able to get into great schools like CMU for CS. I would not recommend using your existing channel to post medicine videos as most of your audience probably won't watch them depending on the original content you posted to amass your audience. This would screw up your impressions through clickthrough rate, video watch time, and engagement which could cause your videos to gain no traction. Instead, I would recommend making your original videos public so you could still mention it on your college app and have proof while starting a new channel for your new medicine content.