Tymoshenko arrived in the German capital Friday night and immediately checked into the Charite, one of Europe's largest hospitals, where doctors performed scans on her back.
"We can't say how long she will have to stay here. That depends on what therapeutic path is taken," said Dr. Karl Max Einhaeupl, the hospital's chief executive, who visited Tymoshenko during her 2 1/2 years in jail on charges of abuse of office.
Western governments had condemned her seven-year sentence as politically motivated, and Tymoshenko's early release was greeted as a significant event following the ouster of pro-Russian President Viktor Yanukovych. Although she now holds no formal post, she is believed to wield considerable political influence and a possible contender in Ukraine's May 25 presidential election.
Einhaeupl said he didn't expect her to engage in political activity while in Berlin, but doctors wouldn't forbid it.
He said doctors would perform more tests and decide by Monday whether to recommend an operation. Until then, she is receiving medication and doing physical rehabilitation exercises.
If Tymoshenko does have an operation - a routine procedure that can be done in under an hour - the recovery would typically last about four days followed by rehabilitation over several weeks, he said.
Tymoshenko refused to receive invasive medical treatment while in prison, fearing that political opponents might seek to injure her further.
One common treatment for her condition, known as infiltration, involves injecting painkillers and anti-inflammatory drugs into the site of the slipped disc.
The limited treatment that Tymoshenko did receive in prison to relieve pain and prevent her condition from worsening appears to have improved the first slipped disc, which she suffered in October 2011, Einhaeupl said.
In her public appearances in recent days Tymoshenko looked much better than she did immediately after her release, when she appeared on a stage in central Kiev in a wheelchair looking pale and worn out.
Dr. Anett Reisshauer, who oversees rehabilitation at the Charite, said Tymoshenko's improvement reflected the relief of freedom. Stress can impair the back muscles, which in turn affects the spine, she said.
While she isn't experiencing any paralysis, Tymoshenko requires a mobility aid to walk because she cannot put strain on her right leg, Einhaeupl said. Any long-term damage to the nerves in her back would become apparent only during the course of her treatment.
"I can't tell you whether she will recover completely but I'm confident that ... she will be able to walk unaided," he said, adding jokingly: "Whether she can still take part in the pole vault is something I can't say right now."
Asked whether the German government, which had invited Tymoshenko to come to Berlin, would be paying for her treatment, Einhaeupl said the patient would settle the bill herself.
AP reporter Maria Danilova in Kiev, Ukraine, contributed to this report.