Medical schools require applicants to complete a specific set of prerequisite courses before matriculation. These courses provide the scientific foundation for the medical school curriculum and are tested on the MCAT®. Completing them with strong grades is one of the most important components of your application. This page lists every required and recommended course, explains how prerequisites differ between MD and DO programs, and addresses common questions about course selection.
Core Prerequisites (Required by Nearly All Medical Schools)
Biology: Two semesters of biology with lab (typically General Biology I and II or Introductory Biology sequence). These courses cover cell biology, genetics, evolution, ecology, and organismal biology. Some schools accept AP® Biology credit in place of one semester, but most prefer or require that you take college-level biology regardless of AP® credit. Strong biology performance is essential because it correlates most directly with first-year medical school coursework.
General Chemistry: Two semesters of general chemistry with lab (General Chemistry I and II). Covers atomic structure, bonding, stoichiometry, thermodynamics, kinetics, equilibrium, acid-base chemistry, and electrochemistry. General chemistry is a prerequisite for organic chemistry, so you typically take it during freshman year. See our general chemistry study guide.
Organic Chemistry: Two semesters of organic chemistry with lab (Organic Chemistry I and II). Covers carbon-based molecular structure, reaction mechanisms, stereochemistry, functional groups, and synthesis. Organic chemistry has a reputation as the most difficult pre-med prerequisite, and it is the course where many students question their commitment to medicine. Strong study strategies make a significant difference. See our organic chemistry study guide.
Physics: Two semesters of physics with lab (typically algebra-based physics, though some schools accept or prefer calculus-based). Covers mechanics, thermodynamics, waves, optics, electricity, magnetism, and modern physics. Physics content appears on the MCAT® Chemical and Physical Foundations section. See our physics study guide.
Biochemistry: One semester of biochemistry (some schools require two semesters or accept it as strongly recommended rather than required). Covers amino acids, protein structure, enzyme kinetics, metabolism, molecular biology, and signal transduction. Biochemistry is heavily tested on the MCAT® and is one of the highest-yield courses for medical school preparation. See our biochemistry study guide.
English/Writing: Two semesters of English composition or writing-intensive courses. Medical schools want to see that you can communicate clearly in writing, a skill you will use daily for clinical documentation, research publications, and patient communication. Any college-level English, writing, or humanities course that involves substantial writing assignments typically satisfies this requirement.
Mathematics: One to two semesters of mathematics, typically including statistics. Some schools require calculus; others accept college-level math of any kind. Statistics is increasingly required or recommended because evidence-based medicine relies on statistical analysis. See our statistics study guide.
Recommended Additional Courses
Beyond the core prerequisites, many medical schools recommend (and some require) additional coursework in psychology (tested on the MCAT® Psych/Soc section), sociology (also tested on the MCAT® Psych/Soc section), genetics (deepens your understanding of molecular biology and is relevant to the MCAT® and medical school), anatomy and physiology (directly relevant to first-year medical coursework), cell biology or molecular biology (extends your biology foundation), microbiology (relevant to infectious disease content in medical school), and public health or epidemiology (increasingly valued as medical education incorporates population health). Taking these recommended courses strengthens both your MCAT® preparation and your readiness for medical school, even if they are not strictly required.
MD vs. DO Prerequisites
MD programs (applying through AMCAS®) and DO programs (applying through AACOMAS®) have similar but not identical prerequisite requirements. Most DO schools accept the same core prerequisites as MD schools. One important difference is that AACOMAS® uses grade replacement for repeated courses (if you retook a course and earned a higher grade, AACOMAS® uses only the higher grade), while AMCAS® does not (both grades are included in your GPA calculation). This policy makes DO programs particularly accessible for students who had early academic difficulties and demonstrated improvement through retaken courses. Check the specific prerequisites for each school on your list, as requirements vary. See our AACOMAS® guide and MD vs. DO comparison.
When to Take Prerequisites
A common sequence is: freshman year (general chemistry, biology, English, math), sophomore year (organic chemistry, physics, psychology), junior year (biochemistry, sociology, genetics, upper-level electives), senior year (remaining requirements and recommended courses). This sequence allows you to take the MCAT® in the spring of junior year or the summer before senior year, after completing most prerequisite content. See our pre-med timeline for the full semester-by-semester plan.
AP Credit and Prerequisites
Whether to use AP® credit to skip college prerequisites is a strategic decision. Many pre-health advisors recommend retaking prerequisite courses in college even if you have AP® credit, because medical schools want to see your performance in college-level science courses, the college version often covers material in greater depth than AP®, and a strong college science GPA is one of the most important factors in your application. However, using AP® credit to place into advanced courses (taking Genetics or Molecular Biology instead of Intro Biology, for example) can work well if you are confident in your preparation and perform well at the advanced level. Discuss this decision with your pre-health advisor based on your individual preparation and goals.
For study strategies across all prerequisite courses, see our academic resources section. For GPA considerations, see our GPA calculator guide.
Course Sequencing Strategy: The order in which you take prerequisites matters. General Chemistry must come before Organic Chemistry (orgo requires gen chem knowledge). Biology should be completed early because it provides context for biochemistry and upper-level courses. Physics can be taken at any point but is typically scheduled sophomore or junior year. Biochemistry should be taken before you take the MCAT®, as it is one of the most heavily tested subjects. If you are planning to take the MCAT® in the spring of junior year, ensure that you have completed or are currently enrolled in general biology, general chemistry, organic chemistry, physics, biochemistry, psychology, and sociology by that point. Missing prerequisite content at MCAT® time is one of the most common reasons for lower-than-expected scores.
Online and Community College Courses: A common question is whether medical schools accept prerequisites taken online or at community colleges. The answer varies by school. Some medical schools accept online and community college courses without reservation; others prefer or require that prerequisites be taken at four-year institutions with in-person lab components. The safest approach is to take your core prerequisites (biology, chemistry, organic chemistry, physics) at your four-year university with in-person labs. If you need to take a prerequisite elsewhere (due to scheduling conflicts, summer availability, or cost), check the policies of the medical schools on your target list. See our GPA calculator guide for how different institutions’ grades affect your AMCAS® GPA.
What If You Earn a Low Grade in a Prerequisite: A single low grade (C+ or below) in a prerequisite course is not the end of your medical school aspirations, but it needs to be addressed. Options include retaking the course at your institution (AMCAS® will include both grades in your GPA; AACOMAS® uses only the higher grade), demonstrating improvement by earning strong grades in subsequent, higher-level courses in the same discipline (an A in Biochemistry after a C+ in General Chemistry demonstrates growth), addressing the grade in your application (if there were specific circumstances, your personal statement or secondary essays can provide context), and earning a strong MCAT® score in the relevant section (a high Chem/Phys score can partially compensate for a weak Chemistry grade). What you should not do is ignore a weak prerequisite grade and hope no one notices. Admissions committees will see it, and they will want to know what you did about it.
References
Association of American Medical Colleges (AAMC). “Medical School Admission Requirements (MSAR).” AAMC, 2025. https://www.aamc.org/services/medical-school-admission-requirements. Accessed March 2026.