Hamlin is undergoing evaluation at Buffalo General Medical Center/Gates Vascular Institute in the state of New York, having been released from University of Cincinnati Medical Center on Monday.
The 24-year-old said he is passing medical examinations and asked well-wishers to keep him in their prayers.
"Damar Hamlin remains hospitalized, but is in good spirits, at Buffalo General Medical Center/Gates Vascular Institute, a Kaleida Health facility in Buffalo, NY," read a tweet from the Bills.
"Hamlin is going through a series of testing and evaluation today."
Hamlin's heart stopped nine minutes into last Monday's match at Paycor Stadium after he collided with Bengals wide receiver Tee Higgins.
"Not home quite just yet," he tweeted. "Still doing & passing a bunch of test.
"Special thank-you to Buffalo General it's been nothing but love since arrival! Keep me in y'all prayers please!"