A day in a District hospital costs an average of $218 a day, nearly double what it was five years ago.

At the same time, a typical type of non-group health insurance coverage supplied by Blue Cross-Blue Shield will soon cost subscribers in the District $71.40 a month, compared to a monthly rate of $29.43 five years ago.

Rising costs like these, health specialists say, are partly due to overexpansion of hospitals, sophisticated medical equipment and health services. One way to curb the overexpansion, they add, is planning - planning that would look at existing medical facilities throughout the metropolitan area before building more.

The District has taken a step toward regional planning that would look beyond its own borders by signing an agreement with two neighboring jurisdictions to prevent unnecessary duplication of hospitals and other health services.

The assistant director of human resources for state agency affairs in the District, Jacqueline Johnson, signed the agreement last week with three health planning agencies in Northern Virginia and suburban Maryland.

"The agreement opens up a strong possibility that as a region, we will be able to control the growth of hospitals and additional beds," said Joseph Payne, acting director of state health programs for the District. "Our signing of the agreement helps strengthen the cooperative atmosphere among the jurisdictions in health planning."

The agreement calls for all the health planning groups to join forces to combat overexpansion of health facilties throughout metropolitan Washington.

The District originally had not planned to sign the agreement, since it is waiting for federal designation and funding as a local health planning agency. Payne says he expects designation by March 1.

"Without the funding for more staff to handle the information exchange and other provisions of the agreement, we will be under quite a bit of additional work for the moment," Payne said. "But we would have participated in the agreement even if we had not signed it."

The health planning groups will continue to make decisions concerning health care in their own jurisdictions.

But representatives from each of the agencies, according to the agreement, will exchange reports and views and invite each other to sit as non-voting members when the organizations examine new requests for medical buildings and equipment.

"That agreement also calls for periodic meetings among representatives of the agencies," said Dean Montgomery, director of the Northern Virginia Health Systems Agency. "But we will probably try to set up monthly meetings to keep up a strong croscurrent of information."

"Until now, the District had nothing to do with what hospitals went up out in the suburbs," Payne said. "Now we will have some input as to how new facilities outside the District will affect our own health services."

Blue Cross analysts project that at the present rate of construction, the metropolitan area will have more than 1,170 unneeded hospital beds by 1980, which will cost more than $70 million a year to maintain. Blue Cross maintains that the time for regional effots to control health care overexpansion and the consequent higher costs is long overdue.

The agreement not only provides for the exchange of information in frequent inter-jurisdictional meetings, but also sets up a data base complied from information gathered by the individual agencies. It also calls for the development of common positions on health planning issues and the establishment of criteria to identify health facilities or projects that would affect more than one jurisdiction.

Under the criteria, proposed health programs or facilities would be considered to have a metropolitan-wide effect if a significant number of people crossed jurisdictional boundaries to use them; if they affect the delivery, cost or quality of services in another jurisdiction, or if the proposed service is highly specialized (e.g. heart surgery or kidney care) and requires regional coordination to "insure high quality and efficient utilization."

The agreement comes at a time when the Maryland and Virginia health systems agencies are developing their comprehensive plans for health care growth and distribution in their jurisictions.

Input from the individual health planning groups in each other's plans hopefully will produce common positions on health planning issues, a Maryland health official said.

The development of a cooperative health planning scheme for the entire metropolitan area also comes three years after Congress passed a new national health planning act that set a goal to establish strong regional planning bodies to cut across state lines in multistate metropolitan areas.

At various times, District, Maryland and Virginia officials refused to join in a single agency. The new agreement, while not creating one umbrella agency for the region does form a common ground for the separate groups to work toward the same goals - keeping health care facilities well distributed and well utilized, while curbing the rising costs of health care.