The former US president took a backseat from the social media site in 2017 after leaving the White House.
He periodically publishes tweets which either are dedications to important figures, news stories he has read, the work of his charity the Obama Foundation and commentary on historic moments.
But in recent days Mr Obama has ramped up his tweets - focusing largely on health and COVID-19, the disease caused by coronavirus.
Mr Obama has encouraged his followers to social distance, praise healthworkers, and volunteer.
On Thursday, he tweeted: "Some great stories of big-hearted people coming up with new ways to come together - even while remaining apart - to help the vulnerable who face some very tough times ahead."
A day earlier, he said: "As communities have begun to recognise the importance of social distancing measures to 'flatten the curve' on COVID-19 transmission, here's a sober but useful primer on what we should expect in the coming months.
"In the meantime, remember to check up by phone on elderly or vulnerable friends and neighbours who may need our help."
On Monday, he wrote: "Here's a useful summary of the current best thinking among public health experts on how we need to approach the fight against COVID-19 in the coming weeks."
Mr Obama's focus on healthcare is not unusual as one of his main campaign pledges during the 2008 election was to improve accessibility to healthcare for all US citizens.
In 2010, he implemented the Affordable Care Act 2010, known as Obamacare.
The aim of the statute is to slow the rising cost of health care by taking steps to make health insurance more available and more affordable to those who need it the most.
It also requires everyone to carry health insurance or pay a tax penalty.
As part of his presidential campaign, Donald Trump said he would aim to have the Affordable Care Act repealed and replaced with another scheme, dubbed the Health Care Freedom Act.
However a vote in the US Senate in July 2017 - six months after Trump took office - saw the repeal being narrowly quashed by 51 votes to 49.
The deciding vote was cast by Republican John McCain, Mr Obama's opposition in the 2008 election and a long-term critic of Obamacare.
At the time, Senator McCain said: "From the beginning, I have believed that Obamacare should be repealed and replaced with a solution that increases competition, lowers costs, and improves care for the American people.
"The so-called 'skinny repeal' amendment the Senate voted on would not accomplish those goals."