Can i be sacked for having a number of days off work due to an ongoing medical condition?

my partner has had 13 days off work since January (5months), one period was a week when he was signed off by the doctor, the others have been days off due to an ongoing medical condition for which he has tests coming up at the hospital for to determine what is wrong. He is now being given a disciplinary hearing in which the letter states may lead to his dismissal. On a few of the days the paramedics have been called out to his work or he has been sent home by the manager. Can they sack him for this?