The number of blacks in U.S. medical schools is not going to be appreciably changed by the Supreme Court's decision in the Bakke case on admissions policies because the "central" problem occurs long before admission, the nation's leading medical journal will say today.

The basic problem is that far too few blacks apply and not enough blacks are properly educated to apply, Dr. Arnold Relman, editor of the New England Journal of Medicine, will say in an editorial. Blacks over the past four years have made up only from 5.4 to 6 per cent of all applicants, the journal reports, though blacks total 11 per cent of the U.S. population.

The "national soul-searching" over Bakke has forgotten this fact, Relman maintains, though it means there will continue to be too few black medical students and black doctors regardless of any Supreme Court decision and no matter how much medical schools "tinker" with their admission policies.

As the "obvious, sensible, long-term solution," he calls for both new pre-medical education and recruiting programs in high schools, and a sustained new national commitment "to practical social action" to educate poor black children intensively so they will be ready for medical education.

The "Bakke case" is the effort of Allan Bakke, a white, to overturn his rejection by a University of California medical college, which had accepted some minority group students with lower test scores. The Supreme Court has heard his case, and medical educators and minority advocates fear a decision in his favor could shatter the "affirmative action" programs by which they are trying to consider other qualities than test scores alone in their admissions.

The "evidence," Relman says - citing new figures in the same issue - "suggests that if black underrepresentation is to be corrected," affirmative action programs must be developed before college, since programs limited to students already in college are inadequate.

Dr. John A. D. Cooper, president of the Association of American Medical Colleges, said yesterday he agrees with the New England Journal analysis and conclusion. His association reported new figures showing that:

There were only 2,480 black applicants this fall in a total applicant pool of 42,000.

The rapid rise in blacks entering medical schools' freshman classes - from only 266 or 2.7 per cent of all freshmen in 1968 to a high of 1,106 or 7.5 per cent in 1974 - has continued to level off. The proportion of blacks dropped to 6.7 per cent in both fall 1976, and fall 1977.

The problem, said Relman and two University of California at Berkeley scholars, Boyd C. Sleeth and Dr. Robert I. Mishell, is that too few blacks enter the highest education pipeline in the first place, too few opt for medical education at the outset - when they would have to start taking mathematics and science courses, which they often avoid - and some who enter medical school drop out or have to be dismissed.

"Effective programs for black high school students are essential," said Sleeth and Mishell, and these should also help other minorities - American Indians, Hispanics and mainland Puerto Ricans - "who are also seriously underrepresented" in medicine.

Dr. Arthur Hoyte of Georgetown University said yesterday that he agrees with the need for high school recruiting and education. But he said medical schools could do "far more" to seek out and help promising minority students who might not have high test scores at first, but could develop into high quality graduates.

As a long-range effort that "needs financial help," he cited Georgetown's Health Education and Service Corps. It has enrolled 500 District high school students to learn about health and become a pool from which future health workers may come.