In spring 324 BC Hephaestion left Susa, where he had been married, and accompanied Alexander and the rest of the army as they travelled towards Ecbatana.
Piecing the accounts together, it seems as if Hephaestion's fever had run its course for seven days, after which time he was sufficiently recovered for his doctor, and Alexander himself, to feel it was safe to leave him, and for Hephaestion to feel hungry.