Nelson Mandela, 94, has been hospitalized for the last two weeks. After some improvement in his condition, his health became critical again on Sunday and has since remained the same. A quick look at the numerous health problems he has suffered over the years:
While serving his 27-year prison term, Mandela was diagnosed with early stage tuberculosis in 1988 after being admitted to a hospital in Stellenbosch near Cape Town with a bad cough and weakness and having complained of dampness in his cell.
Two litres of fluid were drained from his chest and he spent six weeks recuperating in the hospital before being transferred to a private clinic near his mainland Cape Town prison where he was the facility's first black patient.
"When the report came back from hospital they indicated that fortunately we sent the specimen before there were holes in the lung," he said in 2004.
"I underwent treatment and was completely cured after four months."
In January 2011, Mandela set the nation on edge when he was hospitalised for two nights with an unnamed acute respiratory infection at the age of 92.
He was released in a stable condition for home-based care and intense medical monitoring.
In December, 2012 Mandela underwent nearly three weeks of treatment for a recurrent lung infection and surgery to extract gallstones.
He was admitted on December 8 and allowed to leave on December 26 for home-based care.
He also spent one night in hospital in early March 2013 for what was described as a scheduled medical checkup.
He was readmitted on March 27 for 10 days of treatment for pneumonia when doctors drained a build up of fluid from his chest, known as a pleural effusion.
On June 8, he was back in hospital with a renewed lung infection after his condition deteriorated. He was initially said to be in a serious but stable condition.
Mandela had surgery in 1985 for an enlarged prostate gland that had caused a urinary blockage.
In 2001, he received radiotherapy treatment for prostate cancer and told reporters the following year that he had been given a clean bill of health against the disease.
In February 2012, he spent the night in hospital after a minor exploratory procedure to investigate persistent abdominal pain.
He underwent a diagnostic laparoscopy, or keyhole surgery, in which doctors made small incisions in the abdominal area to probe it with a tiny camera.
Mandela's tear ducts were damaged by years of being forced to smash limestone rocks in the quarry on Robben Island, due to the alkalinity of the stone, leaving them dry and prone to irritation.
He had cataract surgery aged 75 in 1994, a few months after being sworn in as the nation's first black president.
Press photographers were asked not to use camera flash when taking pictures of Mandela.