His condition is critical but stable and he is undergoring various tests in the hospital, army sources said.
Earlier, he was evacuated to the army's base camp at Siachen Glacier from where was flown to Delhi in a special air ambulance.
He was brought to the Palam technical airport and airlifted to the hospital, the sources said.
Thappa, who hails from Karnataka, was found alive yesterday after being buried under 25 feet of snow for six days following an avalanche hitting his post at the altitude of 19,600 feet close to the Line of Control (LoC) with Pakistan where the temperature was minus 45 degrees Celsius.