The opposition Fatherland party, led Tymoshenko, took second place in October parliamentary elections in Ukraine to the ruling Party of Regions.
Tymoshenko is serving a seven-year prison sentence after being convicted on corruption charges stemming from a 2009 deal with Russian energy company Gazprom. Her allies say the charges against her are politically motivated.
Oleksandr Plakhotnyuk, her lawyer, said Tymoshenko will keep to her hunger strike until Ukrainians and members of the international community issue an "appropriate" reaction to the elections.
European observers expressed concern about the "abuse of power and the excessive role of money in this election." Ukrainian leaders brushed off the allegations.
Tymoshenko began her hunger strike in late October. Plakhotnyuk was quoted on her website as saying her health had deteriorated substantially.
"At this point she can barely stand up," he said.
Tymoshenko last year staged a brief hunger strike to protest her treatment in prison.