Giorgos Vichas is not someone with time on his hands. Middle-aged, with a head of thick black hair flecked with grey, he has a look of alert determination - but for a moment his gaze becomes wistful.

"When I was studying to become a doctor what I really wanted to do was travel to places that needed voluntary workers," he says.

In the end, he was able to fulfil that ambition without getting on a plane. Eighteen months ago Dr Vichas co-founded the Metropolitan Community Clinic at Helliniko in Athens, for Greeks who found themselves in need without health insurance.

"The crisis in Greece has caused a humanitarian crisis in terms of the health sector. I never imagined we would have to set up social clinics and work on a voluntary basis," he says.

Like many European countries, Greek citizens pay for their healthcare by a system of insurance, with contributions from employers, the state and the beneficiaries themselves. When someone loses their job, they lose their healthcare plan too.

The state gives them a short period of grace, but then they're on their own and have to stump up the cash for drugs and treatment. When the "troika" of the European Commission, the IMF and the European Central Bank agreed a 240bn-euro rescue package for Greece in 2011 the condition was that the Greek government should make tax system improvements, cut the public sector workforce and lower public spending to reduce its debt burden.

What nobody had really properly considered is the impact of the austerity measures - in particular the detrimental effect on that most vital of public services: health care.

There are now around 40 community clinics operating across Greece. Dr Vichas's clinic has 9,500 patients on the books but with a nationwide unemployment increase of 20% since last year (215,735 people) the number of people flocking to the Helliniko clinic is growing fast.

People come to get treatment and drugs. Stamatis Govostis, a dignified, neatly turned-out man in his late fifties, is in no doubt what would happen to him if it weren't for Dr Vichas and his team of volunteers. "That's easy," he says - his eyes watering with emotion. "I would be dead." He says he feels like an old workhorse who, after working all his life as a waiter, is simply being left to suffer and die.

Dr Vichas says his clinic is the only place in the city where cancer patients can get free chemotherapy. They are also providing 200 families with milk formula for their babies.

The municipality provides the premises for the clinic, on a disused American military base, and pays the overheads. But the medical professionals - which include paediatricians, gynaecologists and cardiologists - work there for nothing.

All the drugs are donated by individuals and pharmaceutical companies. They enter the clinic by the plastic bagful, higgledy piggledy, to be processed by a team of volunteers led by pharmacists. They sort them, date them, label them and store them.

"What we're really proud of is this - it's a bit ugly, but it's our storeroom," says Martha Frangiadakis, one of the volunteers. She started to help at the clinic after seeing fellow Athenians suffering day after day on the streets and on TV.

"You sit in your living room and drink your coffee and say, 'Oh my, people are having such problems!' And you feel terrible. And ok, I come and sort meds once a week - big deal. But it's something."

If the clinic finds itself particularly short of a medicine, it posts a request on its blog. But if the clinic's storeroom can't supply a patient with what he or she needs, it's not uncommon for volunteers to walk with them to a pharmacy and pay for it out of their own pocket.

Katerina Dolianiti and Alexandros Zaganas recently came to the Helliniko clinic in desperation.

Their seven year-old son, Christos, had been diagnosed with angioneurotic edema of the larynx. The pair knew immediately what this meant, since Alexandros has the same rare disorder.

They knew that Christos would be prone to sudden and dramatic swelling that would move rapidly along his body. If the swelling reached his stomach it would be excruciatingly painful - if it reached his face or neck, it would be life-threatening. For this reason, Christos would always have to have with him a syringe filled with a strong anti-inflammatory.

Each syringe costs 600 euros (£520), and Christos might need two or three a month. The family used to own a café and a bar, but both businesses closed during the recession. Now, Katerina and Alexandros are unemployed, like 27% of the working-age population - the highest rate in the EU.

"Every time we go to the hospital they won't see us," says Katerina. "Because we don't have insurance, we can't get the injection. If it's urgent and he needs the injection, sometimes I have to lie and say that I am insured. I don't like doing this but I have to."

Katerina has previous unpaid medical bills of her own, but there is no hiding from the system and they will eventually be added to her tax bill. She is so worried for her son that she checks on him every 10 minutes or so and won't let him play with his brothers - but she is also worried that her unpaid tax bill could land her in jail.

"Thank God that these community clinics are now operating and these doctors are helping - otherwise there would be no way of getting treatment," she says. "People are dying - people do not have insurance and they can't get into hospitals."

Dr Vichas is now acting as an intermediary between the family and a local hospital: he is trying to get to supply anti-inflammatories for free. His clinic has a track record of applying pressure on behalf of patients with complex or serious problems. He recently succeeded in getting the state to waive a 6,000 euro (£5,200) fee for a cancer operation on a patient he had referred himself.

The Evangelismos General Hospital in central Athens is one of the largest in Greece. They have felt the pain of the 23% cut in the Greek health budget - last year, their budget was 103 million euros (£90m), down from 150 million euros (£130m) in 2009.

The CEO of the hospital, Michail Theodorou, runs a tight ship. He says that the hospital has been able to make efficiency savings, and the quality of service to patients has not suffered.

One of his senior doctors is more forthright and frank: Ilias Sioras, a cardiologist and staff representative at the hospital with 25 years' experience, says that the staff are struggling, with nurses sometimes scheduled to work for three weeks without a day off.

Dr Sioras adds that some doctors don't follow the law and ask for all the patients' insurance details. "Every day I break the law," he says. "I never ask for insurance for any patient." He gives patients diagnostic tests for free, and says that as yet, no doctor has been punished for bending these rules.

The Greek health service has been hit by multiple blows since the country's economy was thrown into turmoil. As well as the budget cuts and the care needs of patients without insurance, there has been a migration into the state-sponsored insurance scheme of citizens who had previously paid for private healthcare.

Dr Panos Eustathiou from the Ministry of Health agrees that Greece and the Greek health service are facing difficulties, however he insists that no-one - including non-Greek citizens and Greeks without insurance - is being turned away from hospitals. "Health services continue to be provided to all Greeks," he says.

He also denies that the emergence of community clinics is a sign that the health service is collapsing.

"These are signs of a society operating in austerity and difficulty," he says. "These are positive signs for a civilisation and society - not signs of disintegration."

At the Hellinikon clinic in Athens, Dr Vichas does not see it that way. He says that the government have "disregarded" their patients, although like many Greeks, he feels they are not ultimately to blame.

"We are sure the troika are aware of what is going on," he says. "It is the troika who are manufacturing these policies."

He says that his team cannot continue firefighting the city's health problems forever. He is especially worried about poor children falling behind with their vaccinations and malnutrition among babies with insufficient supply to milk powder.

"You could compare our situation to the story of Hydra and Hercules," he says. "When you cut off the head, and you feel like you have achieved something, another four or five grow."