He made the announcement via Twitter with a photograph of himself signing the filing form at the Board of Elections.
"I filed for re-election to continue to serve as your delegate because I want to keep standing up for our community in these uncertain times," the tweet read.
"It's been a great honor to represent the city of Annapolis and surrounding areas," the Democrat said in a telephone interview Friday. "I think I have made a positive impact, particularly as speaker of the House.
"I've been able to accomplish things I don't think would (otherwise) be available to the city."
Busch, who has lost a significant amount of weight in the last year, acknowledged there have been concerns about his health.
He said he had a violent reaction to strong prescription drugs taken during treatment for skin cancer on his legs. The reaction caused internal bleeding.
Busch said he is under care and on the mend, and he hopes to be back to full strength by the fall.
"Nothing is more important that your health," Busch said. "If I thought that would hold me back, I would not even consider putting that in jeopardy. That comes first, no matter what you do in life."
He said "uncertain times" in his announcement tweet referred to "what's going on in the administration in D.C."
"We have spent a lot of time protecting K-12 education, health care and the environment — all those things are under challenge from the Trump administration," Busch said.
"I feel comfortable with what I have tried to accomplish and I hope to be able to continue."
The district he has represented for 30 years has seen demographic changes. After the 2010 census, the legislature juggled the electoral map, splitting District 30 in two. Busch and Republican Del. Herb McMillan represent the new subdistrict, 30A; Del. Seth Howard represents 30B.
The entire district has one state senator, currently state Sen. John Astle, D-Annapolis. Astle has entered the Annapolis mayoral race, and McMillan is said to be weighing a run for his seat.
McMillan, should he remain in the House race, garnered more votes than Busch in the last election at 14,484 to 14,289.
Asked about others in the race, Busch seemed to take the upcoming election in stride.
"I face challenges every time I run for office, it's nothing new," he said. "They might have four or five people in there. They will have to face their own primary. I can't worry about that, I can only worry about what we think we can do."
He thinks the 2018 race will be a nationwide referendum on President Donald Trump, with an effect on down-ballot races.
He said Democrats have a lot to be hopeful about.
"Throughout the state there are concerns from Republicans, many of whom have ridden on the coattails of other candidates," Busch said.
"They are a little shaken by the prospect, thinking they could be painted with the same thing Trump is painted with."
Busch also noted that many Republicans continuously vote against the issues he has long battled for — the environment, aid to public education and successful health care. He is also concerned about the way some have voted or acted around the issue of civil rights.
"There is an energy among Democrats and Independents going into the election," Busch said. "Anne Arundel still has a slight margin of Democrats over Republicans, but the real swing is the Independents."
When Busch is not banging the speaker's gavel, he works as an athletics director for Anne Arundel County.
Editor's Note: This story has been updated to correct details of the 2014 general election in District 30A.