Scotland's First Minister said she had experienced "mild symptoms" after meeting Sinn Fein vice-president Michelle O'Neill in Edinburgh last week, but said on Twitter on Monday that the impact of the virus had worsened.
"Thanks for all the well wishes. The virus has really knocked me for six the past couple of days," she said.
"So while I hope to be back fighting fit v soon, I'm having to stay at home for now."
She added: "Once again - this time from personal experience - please do get all doses of vaccine if you haven't already.
"Covid can be nasty and vaccination protects against much more serious illness. Right now, I'm feeling extremely grateful for that."