Outlays for Medicare and Medicaid in fiscal 1989 would be cut by $11.9 billion from currently projected spending levels for that year under a budget plan sent to the Office of Management and Budget by Secretary of Health and Human Services Otis R. Bowen.

Bowen also proposed cutting National Institutes of Health funding to about $6.2 billion in 1989 -- about $800 million less than the $7 billion just approved by the House for 1988.

But he said appropriations to combat AIDS should be boosted to $1.145 billion in fiscal 1989, about $175 million above the House's 1988 figure.

All three proposals were suggested last month for inclusion in President Reagan's fiscal 1989 budget, which will be sent to Congress at the start of next year. Although Congress still has not passed the fiscal 1988 budget, planning has already started within the administration on the 1989 requests.

According to summaries of Bowen's plan obtained by The Washington Post, Bowen wants to reduce Medicare outlays in fiscal 1989 by $10.3 billion from the spending level anticipated if there are no changes in the law. Most of the reductions would come from proposals submitted in the past but not approved by Congress.

The documents indicated the administration would propose a $1.6 billion Medicaid cut, including $1.3 billion savings from an "across the board reduction" in Medicaid payments to the states.

Bowen told the OMB he does not want to resubmit a controversial fiscal 1988 proposal to include compensation for radiologists, anesthesiologists and pathologists who treat Medicare patients in the flat payments made to the hospitals for each patient.

Instead, Bowen said, to save money the Medicare payment scale for all physicians except primary care doctors should be frozen instead of increased in 1989, payments for nine overpriced procedures cut and payments to doctors cut for inappropriate admissions.

Medicare patients would have to pay more than now for doctor services in hospital outpatient departments and ambulatory surgery centers.