But the Tavistock and Portman NHS Trust say the claimants are seeking to "impose a blanket exclusion" on children under the age of 18 being able to consent to medical treatment, which they say is "a radical proposition".
The High Court's ruling is expected to be delivered at 10.30am on Tuesday.
She added: "It is a safe and reversible treatment with a well-established history".
"The court has ruled that there will be a stay on implementation of its judgment until the later of 22 December or the determination of any appeal", they said. "My life would be very different today", she said outside the court. It argued that under-16s can not give informed consent to puberty blockers, a reversible, "life-saving" treatment that prevents trans kids from going through the wrong puberty.
Trans children's charity Mermaids called the judgment potentially discriminatory and an "absolutely devastating blow" for young people who had benefited positively from hormone blockers.
Stephanie Davies-Arai, the founder of Transgender Trend, a support group catering to parents of trans children, said that the organisation has been "inundated" and "swamped" with more than 100 messages from "anxious" parents following the ruling.
The 23-year-old had been prescribed puberty blockers when she was 16.
She added: "Today's ruling sets a unsafe precedent not just for the rights of trans young people, but for all young people".
The judges said in their ruling that it is "doubtful" children aged 14 to 15 could understand "the long-term risks and consequences" of taking puberty blockers and then hormone replacement therapy (HRT), and "highly unlikely" that children under 13 would be competent to give consent.
One of the claimants, Keira Bell, said the clinic should have challenged her more over her decision to transition to a male as a teenager.
In a ruling, Dame Victoria Sharp, sitting with Lord Justice Lewis and Mrs Justice Lieven, said: "It is said therefore the child needs only to understand the implications of taking puberty blockers alone.in our view this does not reflect the reality".
The Tavistock and Portman NHS Trust - as well as University College London Hospitals NHS Foundation Trust and Leeds Teaching Hospital NHS Trust, to which Tavistock refers children and young people experiencing gender dysphoria - argued that taking puberty blockers and later cross-sex hormones were "entirely separate" stages of treatment.
A spokesperson confirmed that no current GIDS patients who take puberty blockers have been contacted yet, due to the a stay on implementation for the time being.