Hartley is a student at the Johns Hopkins School of Nursing. Her roommate reported her missing Tuesday after she didn't return home.
Police said she takes the shuttle bus to school from her home in Charles Village. She was last seen in the 500 block of North Wolfe Street.
"She was in class we know on Monday and apparently she was not feeling good in class. So is that a contributing circumstance to her disappearance? We don't know. We've checked area hospitals right now to no avail so we're asking for the public's help in locating Miss Lauren Hartley," said Baltimore Police Media Relations Chief T.J. Smith.
Police say Hartley suffers from severe migraines and her family and friends are concerned about her wellbeing.
"At this point, we don't have any overt signs of any kind of foul play, but we don't know what led or caused her disappearance," said Smith.
It is a mystery, which has struck fear in the hearts of Hartley's family, which is now traveling to Baltimore from her home state of South Carolina to aid in the search.
"You get an inkling that something just isn't right,” said Smith. “In this particular scenario, again, with the circumstances that have been presented to us, something isn't right now, but we don't have anything else to point to."
If you have any information on Hartley's whereabouts, you're asked to call the Baltimore Police Missing Person's Unit at 443-984-7385.