Ms Suu Kyi was taken into prison in Rangoon on 14 May
The health of jailed Burmese pro-democracy leader Aung San Suu Kyi is a cause for "grave concern", her National League for Democracy (NLD) says.
Ms Suu Kyi, 63, has not been able to sleep at night because of continuing cramps in her legs and needs urgent medical attention, the NLD says.
She is on trial for violating the terms of her house arrest after a US man came uninvited to her home.
She denies the charges and faces five years in prison if found guilty.
One of her lawyers, Nyan Win, said the court had decided to delay final arguments in her case until 5 June. They had been expected to take place on Monday.
Ms Suu Kyi is widely expected to be convicted at the trial. Observers believe that Burma's military leaders will seize on the incident to keep her behind bars during what they say will be multi-party elections in 2010.
Ms Suu Kyi, who is being kept in Rangoon's notorious Insein prison, has suffered from ill-health in the past.
Shortly before her arrest on 14 May she was treated for dehydration and low blood pressure.
The NLD said she was "in desperate need of proper medical treatment".
"We are very much concerned about her health," it said in a statement.
Ms Suu Kyi has been under house arrest and banned from seeing all but a small group of people for 13 of the past 19 years.
She was arrested on 14 May after an American man, John Yettaw, swam across the lake to reach her compound, spending two nights there.
He and two women who live with Ms Suu Kyi are also being tried.
On Sunday Burma's foreign ministry said in a statement that the pro-democracy leader was "provided with adequate health care and she is in good health".
The ruling junta has also rejected international condemnation of the trial, calling it "an internal legal issue".