The medical laboratory Theranos, facing skepticism about the accuracy of its tests, is planning to announce that it has reduced the size of its unusual board of directors, eliminating members like Henry A. Kissinger and George P. Shultz.

The board is also planning to issue a statement expressing its support for the company and its leader, Elizabeth Holmes.

“We stand wholeheartedly behind the management, achievements, vision and commitment of this company,” the statement says.

Theranos, a privately held company founded by Ms. Holmes, 31, after she dropped out of Stanford at age 19, has been trying to swat down suspicions that the capability it has promoted — being able to do a wide range of medical tests cheaply and quickly using only a finger prick of blood — is more hype than reality.