Can I have a PhD in mathematics or physics after having a bachelor degree in medicine? Can I have a PhD in mathematics or physics after having a bachelor degree in medicine provided that I score high in GRE physics or math?

I have had zero coursework in math or physics but I am not sure if I could greatly increase my chances into grad school by taking GRE and scoring highly in the test.

I'm not trying to show that I'm smart or anything but I think that mathematics is my cup of tea for I'm very passionate about it and I have studied analysis and algebra and quantum mechanics other things from standard textbooks getting help from resources such as MIT OCW.
The hard answer is a straight no.

Doing research level Mathematics or Physics requires a broad set of knowledge and maturity that takes years to achieve. GRE exams are quite crappy, they just ask a lot of questions on basic knowledge and arithmetic; but you won't see an integration by parts (first year maths).

But not everything is lost. There are fields where medicine and maths overlap, and definitely your expertise on one field and interest in learning the other can definitely help. Look at Biomathematics, Bioinformatics, and perhaps, Biophysics. I myself am a Physicist working in Bioinformatics. I do pure analysis of the data, but in the group we also have a wet lab, where my colleagues are trying (among other things) to come up with new creative ways to gather data more suited for our purposes.