The NHS referred 420 patients and staff to police in England and Wales in a year over concerns they were at risk of radicalisation, the BBC has learned.
National Police Chiefs' Council (NPCC) figures show an average of 35 referrals a month in the year to July 2016 - up from 21 a month the previous year.
Since July 2015, public bodies have a legal duty to report people considered at risk of being drawn into terrorism.
The government says its Prevent programme safeguards people at risk.
BBC Radio 5 live used a Freedom of Information request to obtain the figures from the NPCC, which said that, following assessment, one in 10 were found to be vulnerable to radicalisation and offered support.
Those referred undergo an initial assessment and may then be considered by a multi-agency "Channel panel", chaired by the local authority.
If the person is considered to be at risk, they would be offered a mentor and counselling, as part of the Channel programme, a de-radicalisation process that uses psychologists, social workers and religious experts.
Health professionals have previously voiced concerns over referrals.
The Royal College of Psychiatrists warned patients might be less willing to access mental health treatment and questioned the "the variable quality" of evidence underpinning the Prevent strategy.
Some doctors have also said they fear some psychiatric patients have been referred inappropriately.
One former healthcare assistant, who asked not to be named, told the BBC that she was referred to Prevent by colleagues after she started wearing a headscarf at work.
She said she was called to a meeting with safeguarding nurses and a Prevent police officer, and told that allegations had been made by colleagues concerned about some of her social media posts.
She said one photo she shared showed so-called Islamic State members praying in opposite directions because "if they claim to be Muslim, surely they'd know where Mecca is?"
After the meeting, she was told there were no concerns but several weeks later two Prevent officers paid an unannounced visit to her home and asked the same questions.
She said she explained that she was not a risk, but said she has been left feeling paranoid.
"It's been over a year and a half and I'm still not over it. That meeting just changed me, it changed who I was," she said.
As a result of the referral by her colleagues, she felt forced to leave the job she loved, she said, and hated to think what patients would go through in the same situation.
'Knee jerk referrals'
Adam Deen, of the counter-extremism think tank Quilliam Foundation, is an advocate of the scheme but believes better training is needed to avoid "knee-jerk referrals".
He said the fact that most referrals were rejected suggested individuals in the public sector were making inadequate referrals.
There is no breakdown of how many of the 420 referrals in the 12 months to July 2016 were for patients and how many for staff.
However NHS Trust figures obtained by campaign group Docs Not Cops suggested most referrals were for patients, of which a significant number were people with mental health needs.
It found a hospital in Durham referred one staff member and 11 patients.
Birmingham and Solihull Mental Health Trust made 10 referrals and eight mental health patients were referred from Bradford District Care, their figures showed.
'Spot the signs'
A Department of Health spokesperson said: "Radicalising vulnerable people and encouraging terrorist acts is something which NHS staff should treat as a safeguarding issue."
NHS staff training and guidance was being improved so they can "spot the signs and act in the same way they would for any other form of abuse", they added.
Security Minister Ben Wallace said: "Rules for health sector workers on patient confidentiality are the same across all areas of safeguarding, including referrals made because of concerns about radicalisation."
He added that 1,000 people, who had been referred, had been offered support through Channel since 2012.