Transgender people are being put at greater risk of suicide and self-harm because of "unacceptably" long waits for specialist medical clinics in Scotland, according to campaigners.
The Scottish Trans Alliance (STA) said there was a desperate need for the NHS to invest in the services.
It said the health service needed to catch up with the rising number of adults seeking help.
Scotland has four adult gender identity clinics (GICs).
They are based in Glasgow, Edinburgh, Inverness and Aberdeen.
A BBC freedom of information request found that almost 2,000 patients are now under their care, with the number of referrals rising steeply over the past five years.
At the start of 2019, almost 300 people had been waiting more than a year for a first appointment with a specialist.
NHS guidelines say gender dysphoria is a condition where a person experiences discomfort or distress because there is a mismatch between their biological sex and gender identity.
The condition is not covered by the NHS's 18-weeks referral-to-treatment target but the STA thinks the first appointment with a specialist should be within that timescale, because delays can take a "real toll" in terms of depression and anxiety.
By BBC Scotland Health Correspondent Lisa Summers
Gender reform is a controversial issue. The Scottish government's plans to make it easier for people to change their gender in law have been put on hold, and there are particular ethical concerns around the treatment of children with gender issues.
But gender dysphoria has been recognised as a medical condition in the UK since 2002, and, as with any other condition, the NHS has a duty to follow protocols to provide timely treatment and support.
It remains a niche specialism for doctors. But for the very small number of people who need their help, the long waits can have a huge impact.
'It changes how you feel'
Alex McIntosh, who was born Chantelle, was a shy child and struggled with bullying as a teenager. In his early 20s, after finally speaking to his GP, he told his family he was transgender.
There was then a 16-month wait to be seen at Scotland's biggest gender clinic, in Glasgow.
After lengthy psychological assessments, a doctor prescribed hormones to begin his physical transition.
Alex told BBC Scotland he got in the car after seeing the specialist and cried all the way home.
"Everything that I'd worked for had just happened and I was finally going to get what I'd wanted for pretty much 24 years," he said. "It was instant relief and excitement to get it."
Alex now gets hormone injections from the nurse at his local medical practice in Arbroath, every three weeks.
He remembers the first dose vividly.
"It changes how you feel. The next morning you could smell the difference, you could feel the oil on your face the very next morning," he said.
"But now it's fine, it's just the same all the way through. I already had hair on my arms and legs before, but now I've got a bit on my chest coming through."
After his initial long wait, Alex has now joined another queue - to see doctors in Manchester who will be able to perform surgery to remove breast tissue.
Operations like this are not available at all in Scotland, and it will be more than a year before he can get a first appointment in England.
In the meantime, he wears a tight binder to flatten his chest and make his appearance more masculine.
Alex said: "It's going to be six months to a year before the pre-op assessment. But before that it was six months of dieting and weight loss to get below a BMI of 30.
"Now it's just a waiting game. It would be so much better to be able to get the surgery in Scotland.
"It would probably relieve the service and cut down the waiting times, because there would be more options to go through."
Whether he carries on for full gender reassignment surgery will be a decision for further down the line.
Alex has had lot of support from his family and friends, but said the length of the process sometimes gets him down.
"I used to get manic depressive episodes but it's been better recently. I get counselling every two weeks in Glasgow," he said.
"You need to manage your expectations. You put a lot of work into it and you're excited.
"But now I'm stuck in limbo. You get through all the anxiety and then there's a delay and it's a knock."
Long waiting times
Dr Jo Gardiner, a GP near Leith Walk in Edinburgh, has seen a growing number of transgender patients on her practice list.
She works closely with experts from the capital's gender clinic to look after them.
But she thinks the services have become overwhelmed, and the long waiting times are having a serious impact on some patients.
Dr Gardiner said: "They often don't have the same support as other patients. Family and relationships break down when they transition so it can be quite distressing for them.
"Some patients are very isolated and alone and at high risk for things like suicide."
Last year, the average wait to see a specialist in Edinburgh was 324 days. Dr Gardiner said GPs can't do much in the meantime to help people who are desperate to start hormone treatment.
"They are waiting and waiting and I've got my hands tied, I'm not allowed to start a prescription. That's sad," she said.
"When people go to the clinic they get a good service and are seen by caring, understanding people who spend time with them. These people are doing their best - we just need to expand the service to meet the demand."
James Morton, from the STA, said the long waits to begin hormone therapy in particular can put people at greater risk of hate crime.
He said: "If you're trying to live in your gender identity in society, but you haven't been able to access hormones or surgery, then your physical appearance is more likely to indicate you are trans.
"So it can create a high level of risk in social situations and take a real toll in terms of depression and anxiety.
"Some people are waiting up to two years for a first appointment, and it's unacceptable for them to be languishing on the waiting list for so long, without support."
He said it was imperative that the Scottish government and the NHS invested more - but said it would not take a large amount of resources to make a difference.
"We're talking about maybe three or four clinicians across the whole of Scotland," he said. "It's really a pretty small drop in the ocean."
'Isn't rocket science'
Trans people might make up around 0.5% of the population, according to best estimates quoted in a 2018 report by the Scottish Public Health Network (ScotPHN).
It suggested that the rising referral rate for gender clinics might be levelling out, but said the challenge remained to catch up with current levels of demand.
The service also needs to adapt to the growing proportion of younger, questioning, and non-binary people presenting to them according to its authors.
They recommended more resources and specialist training to help reduce delays, and greater support for patients who are waiting.
A Scottish government spokesman said everyone who needs it should get "timely access" to gender identity services.
He said: "Patient safety is essential and we recognise that specialist surgery is best provided in centres of excellence. NHS National Services Scotland coordinates with the National Gender Identity Clinical Network for Scotland to arrange service provision for patients."
Mr Morton said that better training could also allow GPs to routinely look after trans patients with more confidence.
He said: "GPs prescribe hormones for a whole range of other reasons and they also prescribe far more complicated medication with higher side effects for other health conditions.
"Looking after a trans person's health and prescribing them hormones isn't rocket science."