What are the high school requirements to be a doctor?

The answer will always be: As good as you need to get to the next level of education.

The first question you need to ask yourself is: What kind of grades will I need in HS to get to College/University?

For example, if you need a 87% average to get into a Heath Sciences program at University, this is the "kind of grades" you need in high school to become a doctor.

From College or University, depending on the Med school you apply, you will need a combination of things including grades, which may be averaged over 1, 2, 3 or 4 years. You might have to do a MCAT, letter of intent, volunteer work, experience in the field, interviews etc.

Medical schools won't look at your grades in HS.