Greek state hospitals and staff in greater Athens went on strike Wednesday to protest government spending cuts.
Those cuts allow Greece to continue receiving the loans it needs to avoid default.
Although Greece is poised to receive its second financial bailout, creditors say the country may need more economic help and restructuring.
Concerns over a third bailout surfaced Tuesday as parliament approved a new financial package aimed at keeping Greece from bankruptcy.
That deal, plus the one the country has already received, totals more than $225 billion in assistance for the nation.
Greece had to impose new austerity measures to get the bailout loans.
Notwithstanding, the International Monetary Fund, the European Commission and the European Central Bank warned that the country may still be unable to implement changes quickly enough.
They say Greece's austerity measures and structural reforms "could be accident prone."
Creditors also see "significant risks" that Greece will not lower its debt targets to qualify for more rescue loans.
The country will hold general elections in late April or early May, likely causing further delays to reforms. A new government might also seek to change the terms of the bailout program.
Greece is in its fifth year of recession and would need to recover before debt reduction plans can have much effect.
The Bank of Greece predicts the economy will contract another 4.5 percent in 2012 and remain in recession next year, while unemployment may surpass this year's average of 19 percent.