Theo Morris family say he has been 'hungry for his entire life' as a result of a rare protein disease.
The schoolboy's life is constantly dictated by the tiny amounts of food he can eat each day.
Theo from Urmston in Greater Manchester has Phenylketonuria (PKU) which means he could suffer brain damage if he eats more than 12 grams of protein a day - that is the equivalent of three slices of white bread.
They family say they were given hope when a drug, KUVAN, was approved by National Institute for Health and Care Excellence - which would allow him to manage his condition.
But, despite being due to start last November after funding was approved, Theo's mum Georgina says they were getting extremely concerned the treatment trial had been delayed.
She says doctors at the Royal Manchester Children's Hospital said they still had to wait for the funding they needed to allow them to administer and monitor the treatment.
But, Georgina said the hospital have since called to say the trial would start within the next five weeks - something that was a 'huge relief'.
She says Theo is "very excited to try it" - although he will have to be on an even stricter diet ahead of the treatment.
She said, "It is horrible, her son is constantly starving, but they have to strictly limit his protein intake."
Theo will take a daily tablet and have his blood sugar closely monitored, it will take around a fortnight to know if his body responds to the treatment.
Around one in 1,000 babies are born with the disease every year, but now a drug that could prove a lifeline has been approved for use on the NHS.
After KUVAN was approved by National Institute for Health and Care Excellence - Theo's family had hoped it would transform his life.
There are no guarantees he will respond, but if he does, it could mean he could triple the amount of protein he eats.
Video report by Rachel Townsend when funding for the treatment was improved
"I cried," Theo's mum Georgina Morris said. "I think I spent the whole day crying when I heard the news - with happiness and with joy."
The company says while they are pleased to recommend the drug, which will be made available on the NHS until its user reaches the age of 22.
They added: "It’s disappointing not to have been able to extend the recommendation to all adults.
"Even when considering some additional potential benefits of sapropterin in this group, the price of the drug was too high to allow it to be considered an acceptable use of NHS resources.
"The committee were aware that generic products could be available in the near future and hoped these would be priced to allow access to this drug for all adults with PKU.”
Georgina, said: "Theo is eight years old and things have progressed hugely so I'm hoping by the time that Theo gets to the age of 21 things will have changed again.