Paddy Igoe, from Coventry, who needs a bone marrow transplant, has aplastic anaemia and has to have blood platelet transfusions every week.
The football-mad boy's battle is even harder than normal because he has a rare tissue type and his mother Donna told Sky News they are "desperate for healthy people aged 17 to 55 to join the Bone Marrow Register".
Aplastic anaemia is a rare and serious blood disorder caused by the bone marrow not functioning properly.
In people with the condition, the bone marrow fails to produce enough of all three types of blood cells - red, white and platelets.
Mrs Igoe told The Kay Burley Show: "Only 20% of the UK population are on the register and it's just not enough.
"We need to educate people because it's such a simple procedure. Three mouth swabs and a consultation form and that's all you need."
And, if called to give bone marrow, the process is equally straightforward.
"In 90% of cases, it's like giving blood. It takes a few hours," she said.
Ms Igoe went on to say her son who suffers intense fatigue "has been really brave throughout the whole thing", adding: "We literally cannot wake him up in the mornings".
"I can't play football, I can't go out with my friends or on my bike because my platelets are too low," Paddy said.
"He is a normal, energetic 12-year-old lad but his life is governed by hospital appointments and weekly transfusions," Ms Igoe added.
The pair's week is dominated by his treatment, she explained.
"On Monday we go down to London, we go to Great Ormond Street [Hospital] on Tuesday, come back home and we normally go to hospital on Wednesday for IVs and then on Friday for IVs, too."
As part of their Paddy's Plea campaign, set up to encourage people to join the register, the family has been running promotional drives around Coventry.
The Igoes' world was turned upside down when Paddy fell ill on New Year's Eve.
Assuming it was a "tummy bug", his parents ignored it, but when he didn't improve, they took him to their GP at the end of January.
After tests, the doctor told them to take him to a walk-in unit and he was diagnosed with suspected leukaemia at Birmingham Children's Hospital.
Ms Igoe said they are grateful that was proved not to be the case, but Paddy's condition remains severe.