Thousands of people have signed up to register as blood stem cell donors after an online campaign was started by a 13-year-old girl from Winchester.
Zara Al Shaikh set up the Twitter account @Match4Zara to encourage people to sign up to the Delete Blood Cancer UK register.
She is urgent need of a bone marrow transplant but has a very rare tissue type because of her mixed Arabic and British ethnicity.
Her initial Tweet last week has been retweeted almost 10,000 times.
The teen needs a blood stem cell donation to treat her leukaemia - so far a matching donor has not been found.
The charity said that as Zara's heritage is half-English and half-Arabic, those who share her background in particular are being encouraged to register as this is likely to provide the most suitable match for her.
Zara was diagnosed with myelodysplastic syndrome when she was 11 which has now transitioned to leukaemia.