D.C. General Hospital, the city's only full-service public medical center, which has a large clientele among the impoverished, has received a full two-year accreditation by the national Joint Commission on Accreditation of Hospitals.

The action restores the huge Southeast Washington facility to the top-ranked medical status it enjoyed before 1975, when it lost accreditation entirely. In 1978, it received the first of three one-year certifications, which in effect represented probationary status, pending completion of a $20 million construction and renovation program and administrative reforms carried out under a D.C. General Hospital Commission substantially independent of the city administration.

Gilbert Hahn Jr., the commission chairman, said the restoration was "a recognition of the high quality of care provided" to hospital patients. Hospital administrator Robert B. Johnson credited "the hard work of all our employes."

The hospital received another push forward recently when U.S. District Judge Barrington D. Parker dismissed a class-action lawsuit filed in 1975 by senior citizen groups accusing the hospital of maintaining substandard records and facilities.

A neighboring facility, the voluntary Hadley Memorial Hospital, recently won a similar two-year accreditation. But the National Naval Medical Center at Bethesda, the Navy's medical flagship, has been threatened with the loss of its accreditation because of purported shortcomings.