Bindura - President Robert Mugabe was once so sick from food poisoning he thought he was going to die, Zimbabwe’s First Lady Grace Mugabe has claimed.The First Lady said her husband was given medicine intravenously and couldn't rise from his bed."He spent two weeks experiencing diarrhoea but we never made a noise about it," she said, in comments carried by NewZimbabwe.com.Mugabe even summoned cabinet minister Sydney Sekeramayi, a Swedish-trained medical doctor because he felt he was on his deathbed, Grace said, speaking in Shona at a Zanu-PF rally on Saturday."My husband asked me to call Sekeramayi to come and see him before he died and I called Sekeramayi who entered his bedroom when he was hardly able to wake up from his bed," she said, without giving a specific date for the incident.She added: "My husband went through food poisoning for sure… but he never went publicly about it."The revelation at the rally in the northern town of Bindura was a jibe at Vice President Emmerson Mnangagwa, whose allies claimed he was deliberately poisoned by political foes at a similar rally in August.Mnangagwa’s faction is said to be opposed by one aligned to the First Lady.The revelation that Sekeramayi was summoned by Mugabe at a time of severe ill-health will likely fuel speculation that the quietly-spoken politician was favoured to succeed Mugabe.But on Saturday Mugabe ruled out choosing a successor, saying it would be against the party's constitution.At 93, Mugabe’s health is a source of constant speculation. The president makes regular trips to Singapore for health check-ups, though officials say these are specifically related to his eyes.