Greek doctors and pharmacists have gone on strike in the country's first walkout of 2012.
State hospital doctors have said they will treat only emergency cases until Thursday, in protest at changes to healthcare provision.
Pharmacists are angry at government plans to cut the cost of medicines in an attempt to reduce state spending.
A government spokesman warned on Monday that Greece needed more reforms to meet the terms of an international bailout.
Pantelis Kapsis told Greek television that the unity government led by Lucas Papademos could not afford to postpone austerity measures it had agreed with the EU and IMF as part of a second bailout deal last October.
In total, Greece has secured 240bn euros (£200bn; $310bn) in bailouts. The latest requires Athens to reach an agreement with private creditors to write off 50% of the value of the Greek bonds they hold.
Pharmacists went on strike for 48 hours on Monday arguing that government cuts to social welfare meant they could no longer continue to operate.
The Panhellenic Pharmaceutical Association complained that social insurance funds owed its members 400m euros and said a 3% cut in the profit margin on medicines would harm them further.
Greek Health Minister Andreas Loverdos said that lowering the price of medicines would save 90m euros this year.
Athens is trying to cut health spending from 10.6bn euros in 2009 to 7bn this year.
Despite their decision to go on strike for four days, hospital doctors have said they will staff clinics but treat only emergencies.
Last week, tax officials went on strike over salary cuts and workers at Greece's museums and archaeological sites walked out in a dispute over weekend pay.