It is generally recommended that students begin preparing for the MCAT after completing the relevant coursework in the sciences, which typically occurs after the completion of a bachelor's degree program. Therefore, students who have completed their A-levels would typically complete a bachelor's degree program first before preparing for the MCAT.

However, it is never too early to begin thinking about your future academic and career goals, including attending medical school. Students who are interested in pursuing a career in medicine can start exploring the field early on by volunteering at a hospital or clinic, shadowing a physician, or participating in research related to healthcare. These experiences can help students gain a better understanding of the profession and develop the skills and qualities necessary for success in medical school.

In summary, while it is not necessary to begin preparing for the MCAT immediately after A-levels, it is never too early to start exploring your interests and gaining relevant experience in the field of medicine.