Is there a way to be a Doctor and a professional painter at the same time?

You most certainly can. It is a common misconception that if you are pursuing the sciences or medicine, that there is no room for creativity, or simply outside interests. I am a physician educator with Children's Hospital of Philadelphia, as well as an artist. I have to balance my time very wisely so I do not take energy from one or the other. The thing to keep in mind, as Phillip mentioned as well, diluting yourself too much can lead to frustration and sub par work. These fields are vastly different in their scope and level of responsibility. I happened to have started my career as an artist, and then pursued my education background after being well established in the art world. This allowed me the time to focus on something else while being an artist, and to leverage my creativity in a more traditionally scientific and rigid field.

Therefore, my suggestion is to consider which profession is your clear path to commit to and focus on that to the point of expertise. Then, your secondary path can be developed with more thoughtfulness and with less frustration. I've been there biting off more that I could chew...often. I now know that it is critical, especially in your formative years, to exercise patience, focus, and dedication to a particular goal. This can then lead to other paths that can either reinforce your initial focus, or take you in an entirely new direction.

My friend Kathryn Ko check out this article is a Neurosurgeon in NY as well as being an accomplished artist. I work with dozens of docs who are either writers, musicians, artists, act...but they all focused on medicine first, then, once at a level of mastery, could apply more focus to their creative pursuits.

So it can be done, you just have to figure out which is the cart, and which is the horse (i.e. which you are truly will to commit to first).

Best wishes...let me know if you need more clarification.

Kind regards,
~Law

Yes you can but how good your are depends on how much you practice each.