Thousands of transgender adults and children face waits of up to three or more years for gender identity treatment as NHS services come under strain from growing demand.

The number of adults and children being referred to gender identity clinics in England rose from 3,330 in 2014-15 to 8,074 in 2018-19, an average year-on-year increase of around 25%, according to freedom of information data from five clinics offering services.

At the Tavistock and Portman NHS foundation trust, Britain’s first children’s gender identity clinic, the number of referrals for under-18s has almost quadrupled, from 678 in 2014-15 to 2,590 in 2018-19. This equates to an average year-on-year increase of about 40%.

The longest wait for a first appointment across all the five clinics that responded was 1,133 days – more than three years.

Experts said the figures highlighted the lack of capacity in NHS specialised gender identity services. They said long waits for appointments were acutely stressful for patients, with suicide and self-harm a major risk.

Kirrin Medcalf, the head of trans inclusion at Stonewall, said it was positive that there had been a rise in referrals as it showed GPs were becoming more aware of those who need treatment.

“Obviously the waits are really concerning. People should be held to an 18-week referral limit, that is what the NHS has said. When we are talking about a three-year wait, that is over 130 weeks, way over what it should be,” Medcalf said.

“Nottingham now have an average wait for a first appointment of two and a half years, according to their website. The NHS is not being funded properly at the moment and the GICs are generally not expanding at a rate which they are getting increase of patients. The impact on patients is hugely negative. It puts people’s lives on hold.”

At Northumberland Tyne and Wear NHS foundation trust, the number of referrals has risen from 242 in 2014-15 to 520 in 2018-19. There were 806 people on the waiting list for their first appointment as of 1 August 2019.

The longest wait for treatment was at Nottingham Centre for Transgender Health, where a patient waited for 1,133 days. At Northumberland Tyne and Wear trust a patient faced a wait of 1,019 days.

A spokesperson for the Nottingham Centre for Transgender Health said: “In common with many clinics of its type, there are long waiting times for people wishing to use these services. This is due to a national increase in the number of people requiring these services and also a lack of suitably qualified clinicians.”

Sarah Rushbrooke, the group director at Cumbria, Northumberland, Tyne and Wear NHS foundation trust, said: “Our service has waiting times longer than we would like, which reflects the national picture of gender identity services.”

At the Charing Cross gender identity clinic in London, the oldest and largest adult clinic, 6,049 people were waiting to be seen as of the end of September. This compares with 3,938 young people who were waiting at the Tavistock’s gender identity service.

Eli Joubert, clinical lead at the Leeds and York partnership NHS foundation trust gender identity clinic, said the rise in demand was due to trans rights becoming more accepted and support networks on social media encouraging people to seek treatment.

He said: “It’s true to say that all gender services are under pressure. We are funded to see 27 patients a month and get on average more than 100 new referrals a month.”

Samantha Walker has been on a waiting list for gender identity services in London since April 2018 and is still awaiting her first appointment. ﻿She said there was not enough funding at the moment to support those coming forward. “It’s a very minimal approach to the care offered in most cases. It could and should be reviewed.”

Walker said a lot of patients ended up self-medicating. “I know many trans women in the UK and almost all of them have at some point needed to self-medicate. A few months after seeing my doctor it became apparent to me that I wasn’t going to last the waiting time. I did my research, got my bloods tested, sourced my own hormones and started self-medicating. It sounds crazy and extreme, even irresponsible, but if I hadn’t done it I honestly think I would have taken my own life before now.”

At Tavistock, almost three times as many people assigned female at birth (1,740) were referred in 2018-19 as people assigned male at birth (624).

Medcalf said: “I think because parents and society are more tolerant to children who are assigned female at birth behaving masculine. Those assigned male at birth and presenting feminine behaviour is still much more taboo, and parents are less likely to act on that. Children also pick up on that and come out later.”

Bernard Reed, a trustee of the Gender Identity Research and Education Society, said the Guardian’s findings highlighted “the continuing lack of capacity in NHS specialised gender identity services”, which he saidwere not meeting “the exponential increase in numbers of those seeking specialised help”.

He added: “The resultant long waits for a first appointment are acutely stressful. Although gender dysphoria is not itself a mental illness, failure to treat it does cause mental health problems. Self-harm and suicidality are major risks. NHS England is keenly aware of the problem and seeking to solve it but its efforts have not so far been successful.”

An NHS England spokesperson said: “Demand for gender identity services continues to rise as more people feel able to come forward for support and treatment, and we’ve increased investment to respond to the rising demand for these services, with staff working hard to reduce waiting times for patients.”