Ms Sturgeon became Scotland's first female leader in November.
She said she was using her role to champion social justice but her rivals said it had been a disappointing start.
Labour claims she is ignoring the "emerging crisis" in the NHS, while the Tories believe she is too reliant on state solutions to Scotland's problems.
Scottish Lib Dem leader Willie Rennie has accused her of remaining fixated on independence.
Ms Sturgeon succeeded Alex Salmond who stepped down as first minister after a majority of voters rejected independence in September's referendum.
On her appointment, she pledged to build a "social democratic and socially just" nation and vowed to lead Scotland's "most open and accessible" government.
She said some of her key achievements included appointing the first gender-balanced cabinet in the UK, abolishing the poll tax, launching a consultation on land reform and agreeing the delivery of votes for 16 and 17-year-olds in Scotland.
Ms Sturgeon also said she had delivered on the pledge to be open and accessible with online Facebook Q&As and frequent Cabinet meetings around the country.
"When I became first minister I was clear that I wanted to create a Scotland where everyone has the same chance of success, whatever their background," she said.
"That is how we not only improve lives but also grow our economy.
"In the first 100 days of my government we've begun work to achieve those aspirations."
She added: "This week have demonstrated my commitment to helping to break down the barriers that prevent our young people from achieving their full potential.
"I am very proud of the work myself and my team have done so far - but I am also clear that we have much more to do.
"Everything I have learned over the first 100 days has made me more determined than ever - over the next 100 days and beyond - to make Scotland a better, fairer, more prosperous place for us all to live and work."
Scottish Labour leader Jim Murphy said: "We have worse outcomes on A&E than there is in England, and there is an emerging crisis in Scotland's A&E departments.
"The SNP are currently letting down NHS staff and NHS patients by the way they are entirely unfocused on improving the NHS in Scotland.
"So I wish her well, but - must do better on the NHS."
Ms Sturgeon said Scotland's health service had been protected with a budget of more than Â£12bn for the first time and highlighted Â£100m to help reduce the number of people delayed in hospital.
She marked her 100-day milestone with a visit to pharmaceutical company GlaxoSmithKline in Irvine, North Ayrshire, where she announced a new initiative to encourage more young women to take up modern apprenticeships.
Nicola Sturgeon says she is proud of her achievements as first minster but has admitted there is "much more to do" as she marks her 100th day in the role.