The family of a six-year-old boy with epilepsy has applied to the government to be able to use cannabis oil.
Alfie Dingley, from Warwickshire, has a very rare form of the illness that causes up to 150 seizures per month.
His family said his condition improved after using it in the Netherlands – where it is legal – and has given a petition to Prime Minister Theresa May.
During Prime Minister's Questions Mrs May said she wanted the Home Office to look at the application quickly.
His mother, Hannah Deacon, said: "It's a big decision and if they say no, they're condemning our son to death."
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Speaking during Prime Minister's Questions earlier, Jeff Smith, Labour MP for Manchester, Withington, raised Alfie's case and revealed the family had applied to the Home Office for a special licence to use medical cannabis.
Theresa May responded by saying she had met Alfie and his family and that "we want to ensure that people get the treatment that they need" but "it's important that medicines are tested properly".
She said she wanted the Home Office to look at the application quickly.
Ms Deacon, from Kenilworth, told BBC News they applied on Tuesday and have been advised officials will expedite the process based on compassionate grounds and that they hoped to hear something in the within two weeks.
"It's obviously the first time ever it's being done for a person as it is usually a business that applies," she said.
"I am very anxious.. there's a lot riding on this."
She said if the government refuses the licence her son would most likely have to take intravenous steroids which can cause psychosis and problems for his organs.
The Home Office has previously turned down requests by the family to legally take the drug, saying that cannabis cannot be practically prescribed, administered or supplied to the public and can only be used for research under a licence.