The musician is suffering a side effect from his brain hemorrhage called hyponatremia, which is described as a lack of sodium in the body that leads to seizures.
Michaels, 47, is best known as the front man for the band Poison. He is also a contestant on the current season of TV's "The Celebrity Apprentice."
He has been hospitalized in an intensive care unit since suffering the brain hemorrhage last Thursday. He reportedly was transported to the undisclosed medical facility after suffering a severe headache.
Michaels, who is diabetic, was also hospitalized earlier this month for an emergency appendectomy.
"Due to the severity of his condition, Bret Michaels continues to remain hospitalized in an intensive care unit at an undisclosed hospital. He remains in critical but stable condition according to his doctors," said the posting on Michaels' Facebook page Tuesday.
"Doctors state Michaels is very lucky as his condition could have been fatal," the message continued. "With further testing and rehabilitation, they are hopeful that Bret will gradually improve as the blood surrounding the brain dissolves and is reabsorbed into his system, which can be a very painful recovery and take several weeks to months. Michaels remains under 24-hour observation in the ICU and is in positive spirits. He is responding well to tests and treatments. Even though today was a minor setback, doctors remain hopeful for a full recovery and plan to release more specific information next Monday."