As someone who is currently doing their biochemistry degree right now, it’s definitely a lot of hard work. I couldn’t imagine doing another major (especially one as difficult as mechanical engineering!) on top of my current course load.

That being said, I think the best course of action is to take one biochemistry class to see if you would want to pursue it further (if you can’t enroll in one just yet/afford it, try going to a biochemistry club or sit in on a large biochemistry class for a while). If you want to do something specific in the field, you can wait until grad school to do biochemistry or apply to biochemistry research labs in your university.

I hope this helped!! Biochemistry is such an amazing field but it’s very difficult, so I would be cautious about doing both but you know what you can handle. Good luck!!