The average cost of care for a hospitalized AIDS patient exceeds $1,000 a day, and only one-third of the patients are covered by commercial health insurance, a Richmond hospital reported yesterday.

The study involved 52 AIDS patients hospitalized at least once at Medical College of Virginia between October 1983 and December 1986.

For 81 hospital stays for which complete hospital and doctor charges were known, the cost ranged from $259 to $68,291, with an average of $13,830. The average stay was 14.8 days, at an average daily charge of $1,038.

The study also examined 102 AIDS-related hospital stays for which hospital charges were known but doctors' fees were not. These ranged from one to 73 days, with an average stay of 12.8 days. The average hospital charge, not including doctors' fees, was $11,696, or $856 daily.

Only 36 of the 102 hospitalizations were covered by commercial health insurance. Another 14 were covered by correctional institutions and 26 by Medicaid, while the patients paid for 26.

The biggest portion of the patients' hospital bill was for room and board and daily care, accounting for 30 percent. Other major charges included pathology (22 percent), drugs (16 percent), diagnostic tests (10 percent) and intensive care (7 percent).

The 50 male and two female patients included 35 blacks, 16 whites and one Hispanic.

The study was undertaken by a team led by Dr. Lisa Kaplowitz, assistant professor of medicine at the Medical College of Virginia.