A march and demonstration in London was supported by NHS campaigners who gathered at hospitals around the country, including in Leeds, Huddersfield and Dewsbury.
They called on the government to take action on hospital staffing levels, cash shortages and overcrowding in accident and emergency departments.
Protesters gathered in central London and marched towards Downing Street during the "NHS in crisis: Fix it now" protest, organised by the People's Assembly and Health Campaigns Together.
Speakers included shadow health secretary Jon Ashworth and actor Ralf Little, who told the crowd that Britain's NHS was the envy of the world. He had previously told how his mother was saved by NHS treatment for free when she suffered a stroke. He said the quality of the NHS was threatened by under-funding.
"It's a political choice to leave patients sleeping in corridors," he said.
Royal College of Nurses president Cecilia Anim, speaking at the protest, said there were 40,000 nursing vacancies around the UK and the shortage was affecting services. She said: "I've never in my 40 years in nursing seen anything like this."
Protesters gathered with banners and placards outside Leeds General Infirmary as part of the day of action.
At the Leeds protest John Puntis, a retired consultant paediatrician, said: "The staff who work in this hospital are very overstretched at the moment because of the winter crisis, and this is really because of under-funding of the NHS which has gone on over the past eight years."
Gilda Peterson, of Leeds Keep our NHS Public, said: "We reckon there were between 150-200 people there today. We got a lot of public attention. I think people are fed up of what's happening to the NHS.
"The support of NHS staff is great. They are doing a great job but they shouldn't have to work under the circumstances they are working in."
A Department of Health and Social Care spokesperson said: "We know the NHS is extremely busy, which is why the government supported it this winter with an additional £437m of funding, and why it was given top priority in the recent Budget with an extra £2.8bn allocated over the next two years.
"Despite the extra pressure that comes with winter, the most recently published monthly figures shows hardworking staff treated 55,328 people within four hours every single day, 1,272 more each day than in the same month the previous year.”