A court in the eastern town of Neubrandenburg halted proceedings against Hubert Zafke, 95, indefinitely after he received a doctor's note saying he was unfit to attend the hearing on Monday.
The presiding judge ordered the defendant to undergo a thorough medical examination in a hospital to determine whether the trial could continue, according to an AFP journalist in the courtroom.
Chief judge Klaus Kabisch had suspended the trial shortly after it opened on February 29th, saying a doctor had found that Zafke had "suicidal thoughts and was suffering from stress and hypertension".
Zafke served as a medical orderly at the Nazi death camp in occupied Poland from August 15th to September 14th 1944, a period when teenage diarist Anne Frank was interned there.
Prosecutors charge that Zafke "knew of and willingly supported the industrially organized mass killing of people in an insidious and cruel manner".
Of his time as a medical orderly - a job that for some officers entailed giving lethal injections to inmates - Zafke has claimed to have only performed first aid and treated prisoners while having no idea Auschwitz was an extermination camp.
Zafke's ability to stand trial had long been in contention.
The Neubrandenburg court had initially ruled against a trial, finding that he was suffering from dementia, before an appeals court overturned the decision.
The higher tribunal found that, although he suffered "cognitive impairments" and diminished physical capacity, he could be tried if he was granted regular breaks and close medical supervision.
State prosecutor Thomas Bardenhagen on Monday raised doubts about the latest medical assessment by the court-appointed physician.
"I consider this to be a show put on by the defence," he said.
Bardenhagen filed a motion to determine whether the defendant was taking medication to keep his blood pressure artificially elevated.
But defence attorney Peter-Michael Diestel told reporters after the hearing that his client was "deathly ill".
"There is a big chance he could die in the courtroom," he said.
One million European Jews died between 1940 and 1945 at Auschwitz before it was liberated by Soviet forces.