Activists and healthcare workers descended on St Thomas' Hospital on Saturday to protest against new NHS ID checks and charging rules for migrants.
From October 23rd anyone not entitled to free NHS care will be expected to pay up-front for treatment being accessed either in hospital or in the community.
Campaigners have warned that this could lead to vulnerable people and those with spreadable diseases being deterred from seeking help.
Around 200 people took part in the protest in London while others took to the streets in similar actions in Newcastle and Manchester. Those attending the events heard from patients who have already been affected by additional NHS checks.
"I suffer from an anxiety disorder so I was using the NHS for support, but when they started asking questions and challenging my identity, I became too anxious to even see a doctor," one person said.
Last month, Politics.co.uk reported that the changes, which also apply to children, could see school nurses and health visitors being forced to turn young migrants away.
The organisation Docs Not Cops, which led the protests, said the new rules will destroy the relationship between healthcare workers and patients.
"Eligibility checks directly and disproportionately burden individuals who are ill, from lower socio-economic backgrounds and identify as BME, whether they be legally eligible to NHS care or not," Docs Not Cops campaigner Dr Timesh Pillay said.
"I believe in a healthcare system independent from the policies of the Home Office and UK Border Agency that is freely accessible to all."
The group is planning further action before the rules are introduced later this month.